ML18025B431

Application for Amend to Licenses DPR-33 & DPR-52 Submitted as Proposed Changes to Tech Specs & Mods of Electrical Sys. Responses to NRC 800408 & 0509 Questions Encl

ML18025B431
Person / Time
Site:	Browns Ferry
Issue date:	04/09/1981
From:	Mills L TENNESSEE VALLEY AUTHORITY
To:	Harold Denton Office of Nuclear Reactor Regulation
Shared Package
ML18025B432	List: ML18025B431 ML18025B433
References
TVA-BFNP-TS-156, NUDOCS 8104130162
Download: ML18025B431 (224)

Text

REGULATORY INFORMATION DISTRIBUTION SYSTEi+

ACCESSIOV NBR:8104130162 DvC.DATE: 81/04/09 i

NOTARIZED: YES (RIOS)

DOCKET FACIL: 9 Browns Ferry,4uc1 ear Power Stati onP Uni t 1 Tennessee P 05000259 26 BrOwnS Ferr y I4uCl ear POwer StatiOn< Uni t 2P TenneSSee 05000260 AUTH ~ I AUTHOR AFF1LIATIOI4 MILLSg L ~ "I. Tennessee Valley Author ity RFCIP ~ iVAME RECIPIENl'FFILIATION DENTONtH ~ RE Office of '4ucl ear Reactor Regulationi Director

SUBJECT:

4pplication for amend to Licenses DPR-33 8 DPR 52 submitterI as prooosed cnanges to Tech Specs R mods of electrical sys ~

0ISTRISUTION CQOE: ASSIS TITLE: General COPIES RECEIVES:LTR P ENCL fP SIZE:

Distribution for af ter Issuance of Operating License NOTES:icy:FCAF/NESS 05000259 icy:FCAF/NESS 05000260 RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAHE LTTR ENCL IO CODE/NAliIE LTTR ENCL ACTION: IPPOLITOE T ~ 0g 13 13 INTERNAL: D/DIR,HUM FAC08 1 1 9?R g DIV OF LIC 1 1 IKE 06 2 2 VRC PDR 02 1 OELD RAG AS<IT BR ll 1 1

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TENNESSEE YALLEY AUTHOR/TY CHATTANOOGA. TENNESSEE 37 '01 400 Chestnut Street Tower II April 9, 1981 (p

TVA BFNP TS 156 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation Q~

U.S. Nuclear Regulatory Commission Washington, DC 20555

Dear Mr. Denton:

In the Matter of the Docket Nos. 50-259 Tennessee Valley Authority 50-260 In accordance with the provisions of 10 CFR Part 50.59, we are enclosing 40 copies of a requested amendment to licenses DPR-33 and DPR-52 to change the technical specifications of Browns Ferry Nuclear Plant units 1 and 2 (Enclosure 1). The proposed technical specifications are needed to accommodate operation of Browns Ferry units 1 and 2 with a modified electric distribution system. A schedule for performing the system modifications and a description of the modified system is provided (Enclosure 2). Also enclosed are responses to NRC staff questions forwarded to TVA by letters from T. A. Ippolito to H. G. Parris dated April 8 and May 9, 1980 (Enclosure 3). Included in Enclosure 3 are responses to questions the NRC staff had on the license amendment request transmitted by my letter to you dated August 6, 1980 (TVA BFNP TS 143).

The electric distribution system of Browns Ferry units 1 and 2 will be modified in accordance with the enclosed description during the spring 1981 unit 1 refueling outage. NRC approval of the enclosed technical specifications is needed before startup of unit 1, now scheduled for July 23, 1981.

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Mr. Harold R. Denton April 9, 1981 In accordance with the requirements of 10 CFR Part 170.22, we have determined this proposed amendment to be Class III for unit 1 and Class I for unit 2. These classifications are based on the facts that the proposed amendment involves a single safety issue which does not involve a significant hazard consideration for unit 1, and the proposed amendment for unit 2 is a duplicate of the unit 1 proposed amendment. The remittance of $ 4,400 (44,000 for unit 1 and 4400 for unit 2) is being wired to the NRC, Attention: Licensing Fee Management Branch.,

Very truly yours, TENNESSEE VALLEY AUTHORITY M. Mills, Manager Nuclear Regulation and Safety Subscribed,hand sworn to before ae taint~pry" day of ~1981. ~

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Notary Public My Commission Expires Enclosures cc (Enclosures):

Mr. Charles R. Christopher Chairman, Limestone County Commission P.O. Box 188 Athens, Alabama 35611 Dr. Ira L. Myers State Health Officer State Department of Public Health State Office Building Montgomery, Alabama 36104

0 II

ENCLOSURE 2 PROPOSED MODIFICATIONS OF THE ELECTRICAL SYSTEM FOR THE BROWNS FERRY NUCLEAR PLANT SECTION 1 - Background Information on Equipment Installation SECTION 2 - Schedule of Modifications SECTION 3 - Modified System Description

b SECTION 1 E ui ment Installation In preparing the proposed technical specifications it has been assumed that the following equipment will have been installed on

,.- uni.ts '1 and 2 before, unit 1.is started up after the April 1981 refueling outage.

1.'nit station E service transformer, with on-load- tap changer on unit .1;

2. Genei ator .breaker on unit 1.

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3. Solid s'tate undervoltage and overvoltage relays on units 1 and 2 4-kV shutdown boards;

4. Low pressure coolant infection motor generator set on unit 1..

5. Unit station service transformer with on-load tap changer on unit 2.

6. -

System to provide annunciation of 161-kV voltage.

These modifications will provide:

1. Additional offsite 'power sources from the 500-kV system.

2. Improved regulated plant voltage under varying gr id voltage.

3. Improved 4-'kV shutdown system voltage sensing, load shedding, and diesel generator star ting under degraded voltage conditions.

~ ~

SECTION 2 Schedule of Modifications The modified electrical system described in the following section 3 is the proposed permanent arrangement of modifications to correct potential conditions of undervoltage. The electrical system will be configured as described in section 3, with the exception of certain instrumentation and control (IKC) bus modifications, upon startup of unit 1 after the

'cycle 4 refueling outage. Because of delays in equipment delivery the modification on the 120-volt ac power system identified in subsection 8.4.3. 1 and shown on figures 8.4-1 and 8.4-2 of section 3 will not be implemented during, the spring 1981 outage. This modification will be implemented on the I&C power system for unit 2 during the spring 1982 refueling outage and for, unit during the spring 1983 refueling outage.

1 In the interim, the DC system will remain in its,present configuration as shown in the Browns Ferry Final Safety Analysis Report Chapter 8 figures 8.6-1 and 8.7-1, with the auxiliary power system's degraded voltage limit maintained at the existing limit (3920 volt) to ensure proper system operation.

SECTION 3 DESCRIPTION OF PROPOSED PERMANENT ARRANGEMENT OF UNDERVOLTAGE CORRECTIVE MODIFICATIONS FOR BROWNS FERRY NUCLEAR PLANT UNITS,1 AND 2

TABLE OF CONTENTS

8.1 INTRODUCTION

8.1.1 Utility Grid and Interconnections 8. 1-1.

8.1.2 Plant Electrical Power Systems 8.1-1 8 .2 OFFSITE POWER SYSTEM Utility Grid

,

8.2.1 Description of and Preferred Power 8.2-1 8 .2.2 Analysis 8.2-2 8.3 NORMAL AUXILIARY POWER S YSTEM 8.3.1". "

.: General 8 . 3-1.

8.3.2 Power Generation Objective 8.3<<1 8.3.3 ,Power Generation Design Basis 8.3-2

. 8.3.4 Safety Design Basis 8.3-3

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8.3.S Description 8.3-3 8.3.6 Safety Evaluation 8.3-7 8.3.7 Inspection and Testing 8.3-1O

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8.4 120-VOLT AC POWER SUPPLY AND DISTRIBUTION 8.4.1 Power Generation Objective 8.4.1 8.4.2 Power Generation Design Basis 8.4.1 8.4.3 Description 8.4.1 8.4.4 Inspection and Testing 8.4.2

LIST OF TABLES Title'uxiliary Power Supplies and Bus Transfer Schemes

LIST OF FIGURES Title TVA Transmission System - Extra High Voltage Expansion Plan Typical Normal Conditions Loads on USSTs Trip Three Units - Loads of Units 1 5 2 on USSTs, Loads of Unit 3 on CTTs LOCA Unit 1, Trip Units 2 8 3, Shutdown Bus 2'Out, Loads of Units 1 & 2 on USSTs, Loads

,of Unit 3 on CTTs Trip Three Units - Loads of Unit 1 on CSSTs," Unit 2 on USSTs, and Unit 3 on CTTs LOCA Unit 3, Trip Units 1 5 2 Loads of Units 1 & 2 on USSTs, Loads of Unit 3 on CTTs Browns Ferr y 20.7-kV Unit 1 Bus Voltage and Frequency Loss of One Cumberland Unit - Loads on USSTs Browns Ferry 161-kV Bus Voltage and Frequency - Loss of One Cumberland Unit Loads on USSTs Browns Ferry 20.7-kV Unit 2 Bus Voltage and 'Frequency Loss of Browns Ferry Unit 2 Loads on USSTs Browns Ferry 161-kV Bus Voltage and Frequency - Loss of Browns Ferry Unit 2 Loads on USSTs

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LIST OF FIGURES (cont. )

Fi ure No. Title

'

8.2.2-8a Browns Ferry 20.7-kV'nit 1 Bus Voltage and Frequency - Loss of Three Browns Ferry Units Steady State Loads ior Units 1

& 2 on USSTs, Unit 3 on CTTs 8.2.2-8b Browns Ferry 161-kV Bus Voltage and Frequency Loss of Three Browns Ferry Units - Steady State Loads for Units 1 & 2

'n USSTs, Unit 3 on CTTs 8.2.2-9a Browns Ferry 20.7-kV Unit 1 Bus Voltage and Frequency - Three Phase Fault on Unit 2 Terminals - Fault Cleared by Generator Breaker - Loads on USSTs 8.2.2-9b, Browns Ferry 20.7-kV Unit 2 Bus Voltage and Frequency - Three Phase Fault on Unit 2 Terminals - Fault Cleared by Generator Breaker - Loads on USSTs 8 .2.2-9c Browns Ferry 161-kV Bus Voltage and Frequency Three Phase Fault on Unit 2 Terminals Fault Cleared by Generator Breaker Loads on USSTs 8.2.2-10 Browns Fer ry 161-kV Bus Voltage

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and Frequency - Three Phase Fault on Unit'2 Termin'als Steady" State Loadsfor Unit 2-Transferred to CSSTs 8.2.2-11 Browns Ferry 161-kV Bus Voltage and Frequency Loss of Browns.

Ferry Unit 3 Steady State Loads for Unit 3 Transferred to CTTS

8. 3-1e Key Diagram of Normal Auxiliary Power System Units 1 and 2 iV

C LIST OF FIGURES (cont.)

Fi ure No. Title

8. 3-1b Key Diagram of Standby Auxiliary Power System - Units and 2 1

8.3-2 Key Diagr am of Normal and Standby Auxiliary Power System Unit 3 8.4-1 Pl'ant DC and Instrument and Contr ol AC Systems One Line Diagram 8.4-2 Instrument and Control AC System One Line Diagram

0 0

BFNP 0 8.1 8.

1.1 INTRODUCTION

Utilit The Tennessee Grid and Interconnections Valley Authority (TVA) is a corporate agency of the United States"Go'vernment serving the State of Tennessee and parts of six other states in the southeast on the boundaries of TVA is interconnected with electric power companies to the north, west, south, and east of its service area. As

'ennessee.

shown .in Figure 8.1.1-1, the TVA grid consists of interconnected hydro plants, fossil fueled plants, and nuclear plants supplying electric energy over a transmission system consisting, of voltages up through 500 kV.

The Browns Ferr y Nuclear Plant is located in Limestone County, Alabama, at river mile 294 on the Tennessee River approximately 9-miles southwest of Athens, Alabama, and 9 miles northwest of Decatur, Alabama (See Figure 8.1.1-1). The plant is connected into an existing transmission grid supplying large load centers'.

Each of the nuclear units is connected into TVA's 500-kV transmission system. The six 500-kV transmission connections consist of two lines to the Madison '500-kV Substation, two lines to the Trinity 500-kV Substation, one line to the West Point 500-kV Substation, and one line to the Davidson 500-kV Substation.

One additional 500-kV connection will be in service in 1981 to the Cordova 500-kV Substation. The 161-kV switchyard is conne'cted into the 161-kV transmission system through one line to the Trinity 500-161-kV Substation and one line to the Athens, Alabama, 161-kV Substation.

The 161-kV system and the 500-kV system via the. main generator step-up .transformers, employing fully rated generator circuit breakers to disconnect the main generator, provide the Browns Ferry Nuclear Plant with sources of offsite electrical power to meet the requirements of GDC-17.

8.1.2 Plant Electrical Power S stem Under nomal operating conditions units 1 and 2 are supplied electric power from their associated main generator via the unit station service transformers. During normal startup and shutdown the unit's main generator is isolated by a g'enerator breaker, and electric power is supplied to the unit auxiliary power system

,from the 500-kV offsite grid via the main transformers. If electric power from the 500-kV grid is unavailable to a particular uni't, power is then supplied from two 161-kV transmission lines via two common station service ti ansformers.

In addition, two cooling tower transformers provide a the backup bus 'tie source of power for units 1 and 2 shutdown loads via board (Figure 8.3-2).'.1-1

e BFNP 0 The standby source of auxiliary power is from four diesel generator units. These units start automatically on loss of voltage or a degraded voltage on the associated shutdown board from self-contained starting air systems. In the long term following an accident, units and 2 diesel generators will be 1

"'paralleled with their unit 3 counterparts (

Reference:

FSAR Section 8.5,.4.1).

250-Volt d-'c Batter S stems There are nine 250-volt d-c battery systems each of which consists of a battery, battery charger, and distribution equipment. '(One addit'ional 250-V d-c plant battery system will be available in approximately two years). Three of these systems provide power for unit control functions, operative power for unit motor loads, and alternative drive power for a 115-volt a-c unit preferred motor-driven-generator set. One 250-volt d-c system provides power for common plant and transmission system control, functions, drive power for a 115-volt a-c plant preferred motor-generator set, and emergency drive power for certain large motor loads, (e.g.', lube oil pump). The five remaining systems deliver control power 'to their respective 4160-volt shutdown boards.

48-Volt d-c Batter S stems There are three 48-volt d-c battery systems each of which consists of a battery, battery charger, and distribution panel.

Two of these systems provide power to the'wo annunciator systems and the third is the power source for the plant telephone system.

115-Volt a-c Unit Preferred S stems.

The two 115-volt" a-c unit preferred systems are each supplied by its associated motor-generator set which is normally driven by a low slip induction motor supplied from a 480-V shutdown bus.

An. alternate 250-volt d-c drive motor is provided .on the common shaft to provide a continous'15-volt a-c power. source throughout an automatic transfer from the. a-c drive motor to the d-c drive motor.

115-Volt a-c Instrument and Control Power Buses There are two 115-volt a-c instrument and control power buses for-each of the two generating units. Each of the instrument and control power'buses is supplied by 'its.-associated 480- 108/120-

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volt transformers which in turn are each supplied from independent 480-V shutdown buses. This provides an independent 8.1-2

BFNP 115-volt a-c control power bus for each of the redundant instrument and control channels for each unit.

115-volt a-c Plant Preferred S stem A 115-volt,a-c plant preferred system is supplied by a motor-generator set with a 250-volt d-c drive motor that is started upon loss of normal plant a-c power. This system supplies the plant chart drives, clocks, and certain communication equipment.

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MURPHY HILL EXISTING ENV FACILITIES C A R S S. (

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BFNP 8.2 OFFSITE POWER SYSTEM 8.2.1 Descri tion of Utilit Grid and'referred Power The Browns Ferry Nuclear Plant generators are connected into an existing network supplying large load centers. The three generating units are tied into TVA's 500-kV transmission system via six existing 500-kV transmission lines. A seventh line, Browns Ferry-Cordova, will be added in 1981. The 16 1-kV, switchyard is supplied by two 161-kV transmission lines. Th'ese sources have the capacity and capability to meet the requirements of GDC-17.

The 500-kV connec tions consist of two lines 37.42 and 40.26 miles long to the Madis on 500-kV Substation, two lines 10.41 and 10.66 miles long to the Trinity 500-kV Substation, one line 104.57 miles long to the 'Davidson 500-kV substation, one line 118.18 miles long to the West Point 500-kV Substation, and one line 207 miles long to the Cordova 500-Kv Substation (the latter to be placed in service during 1981) .

The 161-kV switchyard is supplied by two 161-kV transmission lines. One of these lines is 10.94 miles long and connects to the Trinity 500-161-kV'ubstation, and the other is 14.33 miles long and connects to the Athens, Alabama, 161-kV Substation. The Athens Substation is, in turn, connected to the Ardmore, Alabama, 161-kV Substation which has direct connections to the Wheeler Hydro Plant and to the Winchester 161-kV Substation. The Trinity-Browns Ferry 161-kV Transmission Line shares a 2.09-mile river crossing with the Browns Ferry-Trinity No. 1 500-kV Transmission Line, crosses under all of the 500-kV transmission lines emanating from the Browns Ferry 500-kV switchyard buses, and is on a common right of way with the Browns Ferry-Trinity No. 1 500-kV Transmission Line for 1.31 miles.

The lines in these'sections are separated sufficiently to ensure that the failure of any tower in one line will not endanger the integrity of the one500-kV or the 161-kV transmission systems. A tower failure at transmission line crossing or in the river crossing could remove from service two 500-kV and one 161-kV circuits while a tower failure in several other areas could remove from service one 500-kV and one 161-kV circuit. The Browns Ferry-Athens 161-kV Transmission Line crosses under the West Point 500-kV Transmission Line near the Browns Ferry Nuclear Plant and continues par'allel with the Browns Ferry-Madison No. 1 500-kV Transmission Line for 0.96 mile and crosses under each end of this 0.96-mile section. The Browns Ferry-Athens 161-kV Transmission Line will also cross under the new Browns Ferry-Cordova 500-kV Transmission Line near the Browns Ferry Nuclear Plant. The lines in this section are separated sufficiently to 0 8.2-1

BFNP ensure that the failure of any tower in one line could remove from service no more than one 500-kV and one 161-kV circuS.t.

TVA's transmission lines are designed to meet or exceed medium loading requirements of the National Electrical Safety Code. On 161-kV lines,, design cases provide for wind loadings of approximately 85 mph wind on bare conductors and vertical loading strength based on approximately 1-inch radial ice. On 500-kV lines, design cases provide for wind loadings of approximately 100-mph wind on bare conductors and vertical loading strength based on approximately 1-1/0-inch radial ice.'These loading conditions assure strength to provide adequate reliability under weather conditions encountered on TVA's transmission system.

The wire tensions for the conductors were selected to assure that vibration does not cause damage to the conductors. Galloping of conductors can occur in the Browns Ferry area. TVA's experience prior to one occurrence of severe ice and wind conditions in 1980 has been that galloping has been damaging (causing phase to phase faults), durS.ng only one incident in the adjacent service area.

This incident occurred a number of years ago on a 46-kV line which had relatively close phase spacing.

Transmission lines in the 500-kV voltage class have two overhead ground wires provided for lightning protection. This shielding has been effective for an area isokeraunic level of 60 and's 0 reflected in the average operating record of only 0.8 flashover interruptions annually per 100 miles of line. The operating record of the Trinity-Browns Ferry-Athens 161-kV Transmission Line is 10 operations in the last six years because of lightning. The use of* circuit breakers with automatic reclosing results in most lightning-caused interruptions being momentary.

One 250-volt d-c battery board is provided in the powerhouse to supply switchyard requirements. Two 250-volt batteries are available. For loss of one battery, a manual transfer to the other battery is required. Another battery will be added by April 1982. The 500-kV equipment will be supplied from one battery and the 161-kV equipment will be supplied from the other. Each transmission line is protected with primary and backup relaying systems and each power circuit breaker is equipped with two separate trip coils.

8.2.2 ~Anal sls The seven transmission lines (six existing and one future) connected to the 500-kV switchyard and the two transmissS.on lines connected to the 161-kV switchyard have sufficient capacity to supply the total required power to the plant's electrical auxiliary power system under normal, shutdown, and loss of 8.2-2'

BFNP 0 coolant accident (LOCA) conditions for any single transmission contingency. Power reaches units 1 and, 2 auxiliary loads from the 500-kV system through the main transformers and the unit station service transformers (USSTs) and from the 16 1-kV system over two physically independe'nt 161-kV transmission lines through

.

the common station service transformers (CSSTs). Auxiliary.power is "suppli'ed to unit 3 for shutdown and LOCA conditions from, the 161-kV system over the two physically independent 161-kV transmission lines through the cooling tower transformers (CTTs). These sources have sufficient capacity to supply all loads regardless of plant conditions. Separation of the lines, the protection systems, and a strong transmission grid minimize the probability of:simultaneous failures of offsite power sources. Steady-'state studies show these offsite sources to be capable of supplying th'e onsite power system when all nuclear units are simultaneously removed from service.

Transient stability studies included a. three-phase fault on a.

generator terminal in which the unit was disconnected automatically from the transmission system as a result of the disturbance. Other transient stability studies included loss of TVA's largest unit, loss of one Browns Ferry unit, and the simultaneous loss of'hree Browns Ferry units. These transient stability cases were considered to be the most serious conditions of postulated transmission disturbances. They show that the J transmission system remains stable with negligible disturbance to the offsite power sources.

Steady-state stud'ies show that the 500- and 161-kV networks are capable of supplying the offsite power requirements for normal, shutdown, and LOCA conditions. Due to the large number of diverse generating units and strong interconnections, the likelihood of an outage, of a sufficient part of the transmission system causing the loss of all sources of offsite power is considered to be* extremely remote . Xn none of the steady.-.state or transient stability cases were the offsite power sources.,

incapacitated because of thermal overloads, voltage variations, or frequency deviations'so as to decrease the reliability of the

'transmission system to supply power to the onsite power systems.

. Figures 8.2-.2-1',through 8.2.2-5 show the power flow around the Browns Ferry 500- and 161-kV buses for (1) typical peak system no'rmal conditions, (2) trip three units with uni'ts 1 and 2 loads '=.

on USSTs and unit'3 loads on cooling tower transformers (CTTs),

(3) LOCA unit 1, trip units 2 and 3, shutdown bus 2 out, with

• units and 2 loads on USSTs and unit 3 on CTTs, (4) trip three 1

units, loads of unit on CSST's, unit 2 on USSTs, and unit 3 on 1

CTTs, (5) LOCA unit 3, trip units 1.and 2, loads of units 1..and 2 on USSTs and unit 3 on CTTs.

8.2-3

BFNP Figures 8.2.2-6a,through 8.2.2-8b show voltage and frequency at Browns Ferry for (6a) the 20.7-kV unit bus for the loss of' 1

1300-MW generator at TVA's Cumberland Steam Plant, which is one of TVA's two largest geherators, and (6b) the 161-kV bus for the loss of the Cumberland unit; (7a) the 20.7-kV unit 2 bus for the loss of Browns, Ferry unit 2 with the loads served from the USSTs, and'(7b) the 161-kV bus for the same condition; and (8a) the 20.7-kV unit bus for the loss of all three Browns Ferry units, and (8b) the 161-kV, bus for the same condition. Figures 8.2.2-9a through 8.2.2-10 show voltage and frequency with a"three phase fault on unit 2 terminals for (9a) the 20.7-kV unit bus, (9b) 1 the 20.7-kV unit 2 bus, (9c) the 161-kV bus,.and (10) the 161-kV bus with the steady state loads transferred to the CSSTs. Figure 8.2.2-11 shows the voltage and frequency of the 16 1-kV bus for the loss of unit 3 with the steady state loads transferred to the

CTTS.

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. Analysis Report Browns Ferry 20.7-kV Unit 1 Bus Voltage

-

0 And Frequency Loss Of One Cumberland Unit"- Loads On USSTs Figure 8.2.2-6a

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Unit Loads On USSTs Flguie 8.2.2-6b

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• Figure 8.2.2-7b

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BFNP 8.3 Normal Auxiliar Power S stem (Units 1 and 2) 8.3.1 General The plant electr ic power system consists of the main generators, the main step-up transformers, the unit station service transformers (USSTs), the common station service transformers (CSSTs), the diesel generator units, the batteries, and the electric distribution system as shown on Figures 8.3-1a & b and 8.3-2. Under normal plant operating conditions the main generators supply electrical power through isolated-phase buses to the main step-up transformers and the unit station service transformers which are physically located adjacent to the Turbine Building. The primaries of the unit station service transformers are connected to the isolated-phase bus at a point between the load side generator breaker terminals and the low-voltage connection of the main transformers. The generator breaker has an interrupting capacity of 165,000 amperes at rated maximum voltage, a continuous current rating of 36,000 amperes with a 4.8 cycle interrupting time, and a rated voltage of 24KV(RMS).

During normal operation station auxiliary power is taken from the main generator through the unit station service transformers.

During startup and shutdown, auxiliary power is supplied from the 500-kV system through the main transformers with the main generators isolated by the main generator breakers. Auxiliary power is also available through the two common station service transformers and cooling tower transformers, which are fed from the 161-kV system. Standby (onsite) power is supplied by eight diesel generator units (4 for units and 2, 4 for unit 3).

1 In the event of a main generator trip during normal operation the generator breaker opens and auxiliary power is supplied from the 500-kV system through the main transformers. Failure of a preferred offsite circuit from the 500-kV switchyard to the main power transformer for units 1 and 2 brings about an automatic transfer for both safety- and nonsafety-related buses. The nonsafety-related buses transfer to the CSSTs. The safety-related buses transfer to the alternate units USSTs if voltage is available. Otherwise, they will transfer with the nonsafety-related buses to the CSSTs. If this supply subsequently fails, only the safety-related buses (Class 1E system) are automatically transferred to the standby (onsite) electric power sources.

8.3.2 Power Generation Ob ective The basic function of the normal auxiliary electrical power system is to provide power for plant auxiliaries during startup, operation, and shutdown, and to provide highly reliable power sources for plant loads which are important to its safety. The 8.3-1

r.

BFNP normal auxiliary power system is to furnish power to startup and operate all the station auxiliary loads necessary for plant operation, and to furnish normal and alternate sources of power for safe shutdown. The emergency sources of power for safe shutdown will be provided by the diesel generator units in the standby auxiliary power system.

8.3.3 Power Generation Desi n Basis

1. The normal auxiliary power system shall be designed to furnish adequate sources and distribution of power to station auxiliaries required for the normal station power-producing function, and for the station common functions necessary to support plant operation in a safe and efficient manner.

2. Redundant off-site power sources, and on-site standby sources shall be available to serve these loads.

3. These sources and systems shall be designed to furnish sufficient power to obtain prompt and safe shutdown of the units, and to maintain the station in a safe condition.

4. The system shall have a high degree of reliability.

8.3.4 Safet Desi n Basis

1. The normal auxiliary p ower system shall be designed to prov ide suffic ient no r mal and alternate sources of power to assure a capability for prompt shutdown and continued maintenance of the plant in a safe condition.

2. The normal and standby auxiliary sources shall be sufficient in number and of such electrical and physical independence that no single event, as a minimum requirement, can negate all auxiliary power at one time.

3. The ca'pacity of these sources when degraded to a fraction of their normal capacity shall be sufficient to supply the power required to'shutdown the plant and maintain condition under normal or accident situations.

it in a safe The buses shall be arranged so that essential loads can be easily transferred to the standby diesel generators.

5. Buses and service components shall be physically separated to limit or localize the consequences of electrical faults or mechanical accidents occurring at any point in the system.

R 8.3.

8.3-2

BFNP 0 Reference Normal is made to Figures 8.3-1a and 8.3-2, Key Diagrams of Auxiliary Power System, which shows the arrangement, source connections, and source ratings for this system. Further reference is made" to Figure 8.3-1b and 8.3-2, Key Diagrams of the Standby Auxiliary Power System, which show the sources into the standby emergency auxiliary power system. Table 8.3-1 is provided to explain the flow of power, transfers between normal and alternate sources, and pertinent operational comments on each of the boards and buses involved in the normal and standby auxiliary power systems.

8.3.5.1 Unit Common Station Service and Coolin Tower Transfor mer s The unit station service transformers are located outside the turbine building near their respective main generator leads with isolated phase bus ducts used for the primary connections. The common station service and cooling tower transformers are located outside the building. One lightning arrester per phase, mounted, directly on the transformer, is provided for each common station service transformer secondary.

The transformers are three-phase, double-secondary, outdoor type, oil filled, class OA/FA and OA/FA/FOA, rated for 55 C temperature rise but with 65 C rise insulation. The transformers are designed, manufactured, and tested in accordance with TVA standard specification 54.080. Transformer secondaries are wye-connected with'esistance-grounded neutrals to provide positive relay operation on ground faults, limit short circuit damage, and to avoid damaging transient 'overvoltage during fault conditions.

Common station service and cooling tower transformers are wye-connected on the 161-kV primary, and each has a delta-connected stabilizing winding. Unit station service transformers have delta-connected 20.7-kV primary.'ach is capable of operating continuously with no loss of life at 112$ of rating at 65 C temperature rise.

Unit station service transformers 1B and 2B, which provide the normal supply of power fo'r operational loads on 4160V A and B unit boards and the safety-related buses from the main generator or 500-kV grid, are equipped with on-load tap changers on the primary winding that can regulate the voltage over a + 10-percent range. Load tap changers operate from signals received from voltage sensors on either of the 4160V transformer secondary windings.'pon receiving a voltage signal outside the limits of a set bandwidth adjustable between 105- to 135 volts (on the secondary of a 4160-volt to 120-volt potential transformer) the v'oltage sensors transmit a signal to the load tap changers to compensate for the voltage change.

0 8. 3-3

0 0

BFNP The on-load tap changers on the unit station service transformers have a voltage r'ange from 18630 volts to 22770 volts with the equivalent of 17 possible tranformation ratios. The time required 'to change a'ap position after receiving a signal from the voltage sensors is 4.0 seconds. Remote manual control, of the load tap changers can also be accomplished from the Main Control Room. The on-load tap changers control circuits will block tap changer operation 'and alarm for sensed voltage outside the permissible range for tap changer operation. Alarms are also provided'or tap changer off position and loss of control voltage.

Both common station service transformers in service are capable of, continuously carrying the load consisting of the station units common auxiliaries, plus all auxiliaries of two generating in the shutdown mode.

The unit station service transformers A and B are capable, of continuously carrying the load consisting of all auxiliaries of,-

one generating unit operating at full load plus the load on one of the two common auxiliary boards and the maximum load on one of the two shutdown buses with another generating unit in the accident mode and the other in the shutdown mode.

8.3.5.2 4160-Volt S stems The 4160-volt unit board switchgear consists of three buses as shown in Figures 8.3-1a, 8.3-1b and 8.3-2. The sections are connected-to the station service transformers so that at least two sources of supply are available to each section. The switchgear sections are heavy duty, metal clad, of standardized unit construction. Circuit breakers are of'he air-magnetictransformer.to type. Power connections from the station service Y-winding of the switchgear are with nonsegregated buses. The the A USST supplys power to the recirculation pump boards.

The unit and common station service transformers, cooling tower transformers, and c'ooling tower switchgear are located outside the powerhouse. All overcurrent relays and devices are selected to provide full selective coordination on overloads, ground faults, and phase-to-phase: faults "throughout the system from

-

station service transformers through motor control center. branch circuit molded-case breakers. All control power for switchgear is supplied from 250-V batteries.

Each switchgear bus section and the star tup buses have their source breakers interlocked .to prevent paralleling power sources, and are provided with manual and automatic bus transfer schemes.

Automatic transfers are initiated by generator and transformer protective relays, degraded voltage or loss of voltage at the 8.3-4

BFNP normal supply, or by accidental tripping of the normal supply breaker. Transfer is blocked through manually-reset lockout relays in case of a faulted bus. Each bus section is provided with a manual-automatic transfer selector switch.

All breakers and transformers are rated according to standard electrical industry practice where the impedance of the source, the short circuit current, and the breaker short circuit current capabilities are taken into account.

Equipment is designed and tested in accordance with NEMA and USA Standards for metal-clad switchgear and power circuit breakers.

Each circuit breaker is provided with 250-volt d-c stored-energy mechanism; mechanism-operated, cell-mounted auxiliary switch with sufficient contacts for all required interlocking; current transformers for metering and relaying;" and necessary switchgear-type auxiliary relays for interlocking station auxiliaries and supervision.

Each switchgear bus section and incoming line is provided with two open-delta-connected potential transformers. Each motor breaker and 4160-480-V transformer primary breaker is provided with two current transformers (one in phase A and one in phase C) for metering and phase overcurrent relaying and one ground sensor 0 current transformer for ground relaying. Each includes induction-type overcurrent relays and an instantaneous ground overcurr ent relay.

Each switchgear bus section has an induction-type undervoltage relay which will trip all motors on the bus in case of prolonged undervoltage.

Primary reading, daily logging, two-element watt<<hour meters are provided on each common station service transformer secondary breaker, each tap from the start buses, and for each motor breaker .

Each transformer secondary breaker, and each start bus tap breaker is provided with three ammeters, one wattmeter, and one voltmeter with a transfer switch. One ammeter and transfer switch is provided on each motor and 4160-480-V transformer feeder. One voltmeter and transfer switch is provided on each switchboard bus section.

Metal-enclosed, group-phase, insulated-conductor bus ducts are provided from common and unit station service transformer secondaries to the start buses or switchgear, for start buses, and connections from the start buses to switchgear.. Bus ducts are furnished with a continuous current rating as required for 8.3-5

BFNP the full transformer'r load rating.

Each switchgear bus and startup bus section is provided with a three-phase set of differential relays of the high-speed induction overcur rent type. Each source and load breaker in each differential zone has three. current transformers for .this use only.

Each. common, unit station service, and cooling tower transfoi mer has differential overcurrent protection. Each secondary breaker is provided with three current transformers for differential r'elaying only.

Each main and bus tie breaker is provided with three current transformers in addition to those for differential relaying, for use with metering and overcurrent relaying. Three induction-type overcurrent relays are provided, two for phase currents and one for residual or ground currents.

8.3.5.3 480-V Loa'd Center Unit Substations Each substation consists of 4160-480-V transformers, primary terminal box, and close-coupled or bus duct connected 480-V, metal-enclosed switchgear .

0 Each substation bus is normally fed from its own transformer, with an alternate source consisting either of an adjacent 480-V bus section or of another transformer serving as standby.

Substations serving station lighting have manually operated main breakers. All other substations have electrically operated main breakers and with the exception of the 480-V shutdown board, automatic bus transfer schemes.

Askarel-insulated transformers are connected to the switchgear the .transformer can be enclosed with a curb to contain the so'hat Askarel: in case of a tank rupture.

,Transformers are liquid filled, askarel 'insulated, three-phase; delta-delta, 60-kV BIL, rated for 55 C temperature rise but with 65 C rise insulation for 12$ margin in continuous capability.

Transformers are class OA/fut FA except where dual ratings are shown in Figures 8.3-1a, 8.3-1b, and 8.3-2, in which cases transformers are class OA/FA. A no-load tap changer handle, with "

means for padlocking, is provided outside the tank.

Main and bus tie breakers and the main switchgear bus are rated 1600 or-600 amperes, depending on the maximum transformer capability, and in accordance with USA Standard C37.16.

Each circuit breaker has.three poles, and is electrically 'and 8.3-6

0 BFNP mechanically trip free with either long time and instantaneous or long time and short time overcurrent trip devices unless overcurrent relays are provided. The circuit breakers have manual or electrical stored-energy closing mechanism, mechanical pushbutton trip, position indicator, and are equipped for mounting on the drawout mechanism in the breaker compartment.

Breakers controlling motors are electrically operated with time and instantaneous series overcur rent tripping.

Breakers serv'ing motor control centers 'or panelboards are manually operated with short time selective and long time series overcurrent tripping.

480-V lighting switchgear have main breakers with short time selective and long time series overcurrent tripping, and have key interlocking between main breaker s.

All other 480-V switchgear have main and bus tie breakers each provided with three current transformers, three induction-type overcurrent relays with hand-reset lockout relay, and circuit breaker control switch.

Each incoming line has two potential transformers, ammeter and switch, voltmeter and switch, wattmeter, undervoltage, and 0 overvoltage relay and auxiliary relay for initiating automatic bus transfer and automatically restoring normal condition. Each two-breaker or three-breaker bus transfer scheme has a manual-automatic transfer selector switch. Each bus section which serves important unit auxiliary motors has two delta-connected potential transformers with voltmeter and switch, and induction-type undervoltage relay and auxilairy relay to trip large motors after prolonged loss of voltage.

Each 480-V main bus section has a ground indicator.

Each electrically-operated breaker has a test pushbutton for electrically closing and tripping the breaker only when the breaker is in the test position.

required 8.3.5.4 480-V Motor Control Centers Motor control centers are in accordance with NEMA Standard IC1.

Circuit equipment consists of molded-case, thermal-magnetic circuit breakers, contactors or starters, and auxiliary relays and timing relays are .

Each starter has one red indicating light, rated 550-V for extended lamp life, connected across the load terminals to indicate that the contactor is energized.

8. 3-7

i BFNP 0 Each single-speed motor starter has two hand reset overload relays. Each two-speed motor starter has two overload relays each speed.

for Starters and contactors are controlled with 120-volt a-c, single-

"phase, ungrounded supplies. Two-'pole, 250-V control fuses are

~

provided at each starter or contactor.

8.3.6 Safet Evaluation Components used in the noi mal auxiliary power system .are those which are widely applied for utility and industrial applications. -In such applications,. the usage frequently'demands reliability comparable to.'hat of the requirements under consideration herein. More specifically, some examples of the .

'components which will be used are General Electric type IAV relays for the detection of bus undervoltage, General Electric type HFA, HGA, and HEA auxiliary relays for necessary multiplication of contacts to achieve simultaneous'unctions, General Electric type CR2820 motor-driven timing relays and General Electric type SB-1 or SBM control switches. These electrical devices are of the heavy duty type, conservatively rated and applied, with many years .of operating experience.

Control power is from the 250-V battery system or from 480-120-volt a-c control power transformers.

The control circuitry is designed to provide certain automatic features as described herein and to allow the operators to take other appropriate action as may be required by the circumstances. The occurrence of automatic functions is adequately displayed in the control room so that the operators can, observe that.proper conditions have been established'. For should one of the 4.16-kV buses fail to be energized 'nstance, after loss of the normal power source, the operator has 'available in the control room the necessary annunciation and manual controls to operate the appropriate circuit breakers.

The;normal auxiliary power system provides adequate power to operate all the- station auxiliary loads necessary for plant operation. The power sources for the .plant auxiliary and'f power supply are sufficient in number and capacity, such ele'ctr ical and physic'al independence that no single probable event could interrupt all auxiliary power at one time. Loads important to plant "'safety are split and diversified between switchgear busses, and means are provided for rapid location and isolation of system faults.

In the event of a total loss of all normal auxiliary power system is supplied from standby diesel V

F so'urces, auxiliary power 8.3-8

BFNP generator units located on the site (safety-related boards only) .

The multiplicity of lines feeding the 500-kV and -161 kV switchyards, the redundancy of transformers and buses within the plant, and the divisions of critical loads between buses, yield a system that has a high degree of reliability. Also, the design utilizes physical separation of buses and service components to limit or localize the consequences of electrical faults or mechanical accidents occurring at any point in the system.

The plant is designed to shut down safely on complete loss of offsite elec'trical power. Standby power is required after shutdown to provide auxiliary cooling, lighting, and miscellaneous services to permit access to plant areas and to assure continued removal of decay heat only external power sources become unavailable.

if the normal Shutdown power normally comes from outside sources as described above. A high degree of reliability in the auxiliary power system contributes to continuity of operation and hence to

"

safety.

If unit generators are incapacitated the generator breaker will be opened and auxiliary power backfed from the 500-kV system.

There are still two other 'independent sources of auxiliary power; the offsite 161-,kV system and the onsite standby diesel generator units. Each source may -be connected to feed the shutdown boards, and each has capacity for operation of all systems required to shut down the unit and maintain it in a safe shutdown condition.

This meets the requirement of GDC 17 of two physically independent circuits.

There are two independent shutdown buses that supply the Units 1 and 2 shutdown boards. These buses are normally connected to the 0-kV unit boards, however, they can be manually transferred to the cooling tower transformers via the 4-kV bus tie board. Unit Table 8.3-1 is a listing of the normal auxiliary power supplies and bus transfer schemes.

At no time will loss of auxiliary power prevent scram s'ince pneumatic energy and normal reactor pressure or stored 'tored pneumatic energy alone a't low reactor pressure are the means of driving in the control rods.

The normal auxiliary power system is operated and instrumented either at the individual unit control boards or at the electrical control board which is common to all three units. The electrical control board is located between units and 2 control boards.

1 8.3-9

BFNP The control functions of the normal auxiliary power system which are unit-related only,'uch as feeder and load breaker operation, are located on the respective unit control boards only. ,The electrical control functions which are shared by units 1, 2, and 3, such as feeder breaker operation to the common 4160-V board, are located on the electr ical control board.

Unit 3 is provided with a centralized control room physically separated, from the common control room for units 1 and 2, but sharing, the same control building bay.

The principal elements of the normal auxiliary electrical system are shown on the electrical system key diagrams in Figures 8.3-1a, 8.3-1b and 8.3-2. All plant auxiliaries except the reactor feedwater pumps, high-pressure coolant infection pump, and reactor core isolation cooling system pump (these are steam turbine-driven) are powered by electric drives. Under startup, shutdown, and for normal operating conditions, all loads

'associated with the reactors and turbine-generator sets are supplied from the unit station service, transformers. Loads associated with the rest of the plant and systems common to units 1, 2, and 3, are 'supplied from the common station service transformers.

Recirculation pump boards 1 and 2 supply 'only the variable frequency generator sets of the recirculation pump motors. The 0 high voltage drop incurred during starting of these large motors can be confined to these buses, and will have no effect on the rest of the system. 4160-V unit boards 1A, 1B, 1C, 2A, 2B, and 2C supply the remainder of the motors associated

with the reactors and turbine-generator sets. Safety-related loads

'required during shutdown conditions are supplied from the shutdown board's. Power to these shutdown buses and boards is normally- supplied from the 4160-V unit boards. If necessary, power will be supplied to the shutdown boards from the standby diesel generators. All shutdown boards are located 'within seismic Class I Build'ings. Each.4160-V shutdown board and each 480-V unit shutdown board and their transformers are physically isolated from each other .

If a unit generator is incapacitated the transformers, the common station service unit station service system," and cooling tower transformers will be used before .it becomes necessary to use the standby diesel generators.

If all sources of pbwer other than the diesel generators are lost, provision is made for-manual connecting the diesel generators to back feed a 4-kV unit board for the purpose of operating a main turbine condenser as an alternate reactor cooling heat sink. Interlocks prevent paralleling the diesel 8.3-10

BFNP gen erators with the normal auxiliary power sources should they urn to availability. Operation in this mode does not interfere with the logic for automatic connection of diesel generators for independent operation upon receipt of an accident signal.

Loads and systems 'which are common to units 1, 2, and 3 except standby emergency systems, are supplied from common boards A and B which are normally fed by the common station service transfor'mers. 7 8.3.7 Ins ection and Testin An extensive and exacting inspection and testing program has evolved as standard procedure for all TVA generating station construction. The procedures are formalized by data sheets, check sheets and reports. ,The program is expanded in the case of nuclear plant construction to include tests required to assure reactor safety and to include expanded operational tests, of functions related to reactor safety. The discussion here is limited to quality assurance and field setting of components in the auxiliary power system. 3

~ 3 7

~ ~

All transformers, switchgear, and motor control centers are sub)ected, as a minimum, to factory tests required under NEMA and ANSI standards. These tests include dielectric tests, electrical and mechanical operation of circuit breakers and contactors, and measurement of transformer constants. Manufacturer's certified test reports are submitted to TVA for review and approval.

8.3.7.2 Ins ection TVA maintains a force of inspectors who 3review the manufacturer's..

work during production, and who permit release of equipment for shipment from thefactory only after assuring themselves that the, equipment is complete, has been manufactured in accordance with the specifications, that specified tests have been performed, and that the equipment is 'of high quality. The equipment is again

,. inspected for damage in shipment before acceptance at the Jobsite.

8.3.7.3 Field Tests

,TVA construction forces perform all tests required to determine that the auxiliary power equipment will function safely, reliably, and as designed; These tests are made prior to energizi'ng the equipment. Examples of these tests are: detailed check of sma'll wir ing,'eggering of all electrical power 8.3-11

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BFNP conductors, phase relation and motor rotation checks. All protective relays and circuit breaker series overcurrent devices are set and tested with laboratory equipment in accordance with setting instructions issued or approved by design departments.

8 .'3-12

Table 8.3-1 Auxiliary Power Supplies and Bus Transfer Schemes - Sheet 1 General Remarks

1. All breakers which may supply a given bus are interlocked to prevent parajleling supply sources.

2. Each bus has provision for manually transferring between normal and alternate sources. Manual transfers of all 4160 V buses are high speed except as otherwise indicated.

3. Bus transfers which are initiated automatically by undervoltage are time coordinated to avoid needless transfer of buses toward the load.

4. The term ~high-speed transfer~ applies to 4160-V bus transfers between stored-energy circuit breakers which are controlled for a dead time not exceeding 5 cyoles.

5. The term delayed transfer" applies to 4160-V bus transfers supervised by bus residual relays, which permit either the normal supply breaker to trip or the alternate supply breaker to close when the bus voltage decays to a value safe for conneoted motors. Normally the residual voltage relay will be set at 30S voltage.

6. Automatic bus transfer is blocked by operation of bus overcurrent or current differential relays for all 4160-V buses. Except for those minor 480-V buses normally supplied from main 480-V buses of the nornal auxiliary po~er system, all 480-V automatic bus transfers are blocked by bus overcurrent protective devices.

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Table 8.3-1 Auxiliary Power Supplies and Bus Transfer.Scheaes- Sheet 2 Item Board and/or Hain Bus Noraal Power Sources Alternate'emarks 4160-V Start bd 1 - Start COH SS TR AI COH SS TR B, Automatic high speed transfer Bus 1A X-winding fed from X-winding fed froa from the normal to the alternate Athens or Trinity Athens or Trinity source is initiated by operation 161 kV lines 161 kY lines of protective relays for the noraal source common station service trans-forner, or for the 161-kV line feeding that transformer. Autoaatic delayed transfer fron the normal t'o the alternate source is initiated by'iae delay undervoltage relays.

The bus will be automatically returned to its noraal, source 40 cycles after return of voltage on the nornal source. This tiae delay is to avoid needless switching during 161-kY line reclosing opera-tions. If alternate source voltage is abnormally low, the normal source breaker will not trip (no transfer); if the normal source breaker trips again within 15 seconds, it will lock out with an alarm, and operator reset will be required. Loss of voltage for a time in excess of 1.5 seconds results in a siggal for autonatic starting of all diesel generators.

2 4160-V Start bd 1 - Start COM SS TR B, COM SS TR A, (See Renarks under Itea 1)

Bus 1B X-winding, fcd from X-winding fed from Athens or Trinity Athens or Trinity 161 kV lines 161 kN lines 4160-V Start bd 2 - Start COH SS TR A, COM SS TR B, (See Remarks under Item 1)

Bus 2A I-winding fed from Y-winding fed iron Athens or Trinity Athens or Trinity 161, kV lines 161 kV lines 4160-Y Start bd 2 - Start COM SS TR B, COM SS TR Ai (See Remarks under Item 1)

Bus 2B Y-winding fed from I-winding fed from Athens or Trinity Athens or Trinity 161 kV lines 161 kV lines 4a 4160-V Bus Tie Board Cooling Tower Transf Cooling Tower Transf Hanual transfer from the normal TCT1 TCT2 power source to the alternate power souroe, or visa versa is provided by operating breakers 1920 and 1930 by means of oontrol switches for these breakers provided on the 4160-V cooling tower switohgear A.

1 Table 8.3-1 Auxiliary Power Supplies and Bus Transfer Schemes - Sheet 3 Power Sources Item Board and/or Main Bus Normal Alternate Remarks Alternate 1 5 Shutdown Bus 1 (4160-V) kV unit bd 1A or 4 kV unit bd 2B or The two independent shutdown buses 2B of preselected 1A (that source not normally supply 4160-V power to on-line unit prese lac ted f or assigned 4160-V shut, down boards, "normal" ) with each bus serving as the normal souroe to two boards and as the Alternate 2 alternate source to the two other boai de. Of, the two possible Same 4 kV unit bd feeders to each shutdown bus from of pre-selected the two 4 kV unit boards, one unit, but fed from feeder .is pre-seleoted manually start bus 1A or 1B as the normal souroe to that bus.

Automatic delayed transfer from Alternate 3 the normal to an alternate 1 source is initiated by undervoltage on Two diesel generators the normal'ource. Automatic i!'equired !'r back- high-speed transfer from the nor-

!'eeding a pre-selected mal to an alternate 1 source 4 kV unit 'bd (lA, 2B) is initiated when the normal source See also remarks for 4 kV unit board normal source items 13, 14, 15, and breaker. trips. If an alternate 1 16 souroe is not available, the transfer,is prevented, and the Alternate 4 normal source becomes alternate 2 source. Automatic trans!'er is Bus tie Board blocked after time delay in. the presence of an aocident signal.

Alternate 3 and 4 sources may be selected manually only.,

Alternate 1 6 Shutdown Bus 2 (4160-V) 4 kV unit bd 1B or 4 kV unit bd 2A (See Remarks under Item 5) 2A, of pre-selected or 1B (that source on-line unit not pre-selected for "normal" )

Alternate 2 Same 4 kV unit bd of pre-selected unit, but fed from start bus 1A or 18 Alternate 3 Two diesel generators, if required for

Table 8.3-1 Auxiliary Pover Supplies and Bus Transfer Schemes - Sheet 4 Pover Sources Ttem Board and/or Main Bus Rormai Alternate Remarks back-feeding a pre-selected-4 kV-unit bd ( 1B, 2A) See also remarks for items 13, 14, 15,, and 16 Alternate 4 Bus tie board 7 - 4 kV Recir culation Pump Boards:

(a) Unit 1; Pump M-G Set 1A Unit SS.TR 1A Start Bus 2A Automatic. high-speed transfer Board 1 T-vind ing from the normal to the alternate source is initiated by main generator unit trip relays.

Automatic delayed transfer from .

the normal to the alternate source is initiated by high-speed voltage relay.

(b) Unit .1, Pump M-G Set 1B Unit SS TR 1A Start Bus 28 0 Board 1 T-vinding (c) Unit 2, Pump M-G Set 2A Unit SS TR 2A Start Bus 2A Board 2 T-winding (d) Unit 2, Pump M-G Set 2B Uni SS TR 2A Start Bus 2B Board 2 T-winding, (e) Unit 3, Pump M-G Set 3A Unit SS TR 3A Start Bus 2A Board 3 T-winding Unit 3, Pump M-0 Set 3B Unit SS TR 3A Start Bus 2B Board 3 T-vinding

' Unit Boards, Unit 8 kV 1 Alternate 1 (a) . 4 kV unit bd 1A Unit SS TR 1B Start bus 1A Automatic high"-speed 'transfer X-winding from the normal to the alternate 1 source is initiated by generator breaker failure relaying, USST protective relaying, main transformer protective relaying, or a comnon trip of both 500-kV svitch yard breakers located between the 500-kV switchyard buses and the 500-kV main transformer bank. Automatic delayed transfer from the normal

Table 8.3-1 0

Auxiliary Power Supplies and Bus Transfer Schemes - Sheet 5 Power Sources Xtem Board and/or Main Bus Normal Alternate Remarks to the alternate 1 source is initiated by a time delay voltage relay.

Alternate 2 Backfeed from shut- manual only through backfeed switches down buses Alternate 1 (b) 4 kV unit bd 1B Unit SS TR 1B Start bus 1B T-w in ding Alternate 2 Backfeed from shut- Provisions are included for down bus backfeeding diesel-generator power from the 4-kV shutdown boards into the 4,160-V unit boards for hot standby shutdown cooling if plant power, other than diesel-all generator power,'s lost. The plant design includes a mode of operation for running one condenser circulating water pump to permit use of the condensers as a heat sink.

Alternate 1 (c) 4 kV unit bd 1C Unit SS TR lA Start bus 1B X-winding 9 4 kV Unit Boards, Unit 2.

Alternate 1 (a) 4 kV unit bd 2A Unit SS TR 2B Start Bus lA X-winding Alternate 2 Backfeed from shut-down buses Alter nate 1 (b) 4 kV unit bd 2B Unit SS TR 2B Stac t Bus 1B T-winding

0 Table 8.3-1 Auxiliary Power Supplies and Bus Transfer Schenes - Sheet 6 Power Sources Tten Board and/or Main Bus Rornal Alternate Renarks Alta'mate 2 Backfeed fron shut-down buses Alternate 1 (c) 4 kV unit bd 2C Unit SS TR 2A Start bus" 1A X-winding 10 4 kV Unit Boards, Unit 3 Alternate 1 (a) 4 kV unit bd 3A'-. USST 4-kV Coding Tower Provisions are included for back'-

X-winding Svitchgear B feeding diesel-generator power fron

• panel 14 the 4-kV shutdovn boards into the 4160-V unit boards for hot standby shutdown cooling if all plant power, other than diesel-generator power, is lost. The plant design includes a node of operation for running one condenser circulating water punp to pernit.use of the condensers as a heat sink.

Alternate 2 Backfeed froo shut-down boards Alternate 1 (b) 4 kV unit bd 3B USST 4-kV Cooling Tower The controls provide for back-T-winding Svitchgear D, feeding fron the shutdown boards panel 7 to the 4160-V unit boards A and B on each unit, vith the boards loaded as defined elsewhere. For units 1 and,2 only, the backfeed is through the shutdovn buses.

(shutdown buses do not serve-unit 3) Backfeed switches associated with each shutdown bus and 4 160-V unit boards A and B, provide for trip and lockout of un't trans-forner and start bus souroes to the selected 4160-V unit boards, before olosure of the selected 4160-V shutdown bus breaker which feeds the diesel generator power fron the

'

Table 8.3-'1, Auxiliary Power Supplies and Bus Transfer Sohenes - Sheet 7 Power Souroes Xten Board snd/or Main Bus Mornal Alternate Besarks shutdown bus to the 4 160-V unit board.

Alternate 2 Backfeed fron shut-down boards Alternate 1 (c). 4 kV unit bd 3C USST 4-kV Cooling Tower X-winding Switchear B, panel 13 1.1 4 kV Connon Board A Start bus 1A Unit SS TR 1A, Autonatic delayed transfer fron the X-winding cornel to the alternate source is initiated by undervoltage on the nornal source, sub)cot to voltage check on the alternate source.

Autonatic delayed transfer back to the nornal source is initiated by return of norsal voltage on the noroal source. Manual transfers in either 'direction are delayed type.

12 4 kV Conson Board B Start Bus 1B Unit SS TR 2A, X-winding Alternate 1 13 4 kV Shutdown Board A Shutdown Bus 1 Shutdown Bus 2 (See also renarks for itens 5 and 6.)

Alternate 2 Autouatic delayed transfer frou the nornal to Alternate 1 source is initiated by undervoltsge on the norsal source, and autonatic return is initiated by nornal voltage on nornal source. Autona .ic voltage transfers froa nornal to Alternate 1 are blocked in the presence of an accident signal.

Diesel generator A Alternate 3 Manual, access con- Autonatic delayed transfer frow the nection to diesel nornal to Alternate 1 source is generator 3A via 4-kV initiated by undervoltage on the shutdown board 3EA norsal source, and autonatic return

Table 8.3-1 0

Auxiliary Power Supplies and Bus Transfer Schemes - Sheet 8 Power Sources Item Board and/cr Hain Bus Homal Alternate Remarks is initiated by normal voltage on normal source. Automatic voltage transfers from normal 'o 'Alternate 1 are blocked in the presence of an accident signal.

'lternate 1 14 -

4 kV Shutdown Board B. Shutdown Bus 1 Shutdown Bus 2 Automatic delayed transfer from the normal to alternate 1 source Alternate 2 is initiated by undervoltage on the normal source, and automatic Diesel generator B return is initiated by normal voltage on normal source. Automatic Alternate 3 voltage transfers from normal to Alternate, are blocked in the presence 1

Manual,- access con- oi an aocident signal ~

nection to diesel-generator 3B,via 4-kV shutdown board 3 EB Alternate 1 15 4 kV Shutdown Board C Shutdown Bus 2 Shutdown Bus 1 All diesel generators are automatically started by an accident signal, loss of start bus voltage (see items 1-4), or by loss of voltage on its shut-down board for 1.5 seconds, or degraded voltage, for 4 seconds After 5 seconds without voltage on the shutdown board, all its supply breakers and all its loads except 4160-480-V tra~vformers are automatically tripped. Alternate 2 source is then automatically connected'anual return to the normal auxiliary power system is permitted if normal auxiliary power.

system voltage retu."ns and if a un1.t is not in- early stage of accident.

Alternate 2 Diesel generator C Alternate 3

Table 8.3-1 Auxiliary Pover Supplies and Bus Transfer Schencs - Sheet 9 Power Sources iten Board and/or Hain Bus Nornal Alternate Renarks Manual, access to diesel gene! ator 3C via 4-kV shutdown board 3 EC Alternate 1 16 4 kv Shutdovn Board D Shutdown Bus 2 Shutdovn Bus 1 Alternate 2 Diesel generator D Alternate 3 Manual, access to diesel generator 3D via 4-kV shutdovn board 3 ED Alternate 1 16a 4 kV Shutdown Board 3EA 4 kV Unit Board 3A kV Bus Tie Bd Provision is cade to nanually select alternate 3 source.

Alternate 2 Diesel generator 3A Alternate 3 Hanual, acoess to diesel generator A via 4-kV shutdown hoard A Alternate 1 16b 4 kV Shutdovn Board 3EB 4 kV Unit Board 3A 4 kV Bus Tie Bd Provisions are included for backfeeding diesel generator pover fran the shutdown boards into the 4160-V unit boards for hot standby shutdown cooling if all plant power, other than diesel generator power, is lost. For this purpose, neans are provided to nanually synchronise 4-kV shutdown boards.

Alternate 2

Table 8.3-1 Auxiliary Power Supplies and Bus Transfer Schemes - Sheet 10 Power Sources Ttem Board and/or Main Bus Normal Alternate R k*

Diesel generator 3B Alternate 3 Manual, access to diesel generator B via 4-kV shutdown board B Alternate 1 16c 4 kV Shutdown Board 3EC 4 kV Unit Board 3B 4 kV Bus Tie Bd Alternate 2 Diesel generator 3C Alternate 3 Manual, access to diesel generator C via 4-kV shutdown board C Alternate 1 16d 4 kV Shutdown Board 3ED 4 kV Unit Board 3B kV Bus Tie Bd Alternate 2 Diesel generator 3D

"

Alternate 3 Manual, access to diesel generator D via 4-kV shutdown board D 17 480-V lister Supply Board Alternate 1 (a) Bus 1 4 kV unit bd 1B Bus 2 (item 17b) Automatic transfer from the normal via TR TQI to the alternate source is ini-tiated by time-undervoltage on the normal source. Return to the normal source is automatic upon return of voltage to the normal source.

Alternate 2

0 Table 8.3-1 0

Auxiliary Power Supplies and Bus Transfer Schenes - Sheet 11 Power Sources Iten Board and/or Hain Bus Nornal Alternate Resarks Bus 3 (Iten 17c)

Alternate 1 (b) Bus 2 4 kV unit bd 2B Bus 1 (Zten 17a) via TR TW2 Alternate 2 Bus 3 (Iten 17c)

Alternate 1 (c) Bus 3 4 kV unit bd 38 Bus 2 (Iten 17b) via TR TN3 Alternate 2 Bus 1 (Zten 17a) 18 480-V Unit Boards Alternate 1 (a) Unit 1, 480-V Unit Bd 1A kV unit bd lA 4 kV con bd B Autonatic transfer fron the nornal via TR TU1A (via TR TEB) to the alternate source is initiated by tine-undervoltage on the nornal source. Return to the nornal source is autonatio upon return of voltage to the nornal source.

Alternate 1 (b) Unit 1, 480-V Unit Bd 1B 4 kV unit bd 1B kV ccn bd B via TR TUlB (via TR TEB)

Alternate 1 (c) Unit 2, 480-V Unit Bd 2A 4 kV unit bd 2A 4 kV con bd B via TR TU2A (via TR TEB)

Alternate 1 (d) Unit 2, 480-V Unit Bd 2B 4 kV unit bd 2B 4 kV con bd A via TR TU2B (via TR TEA)

Alternate 1 (e) Unit 3, 480-V Unit Bd 3A 4 kV unit bd 3A 4 kV con bd A

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Table 8 '-1 Auxiliary Power Supplies and Bus Transfer Schemes - Sheet 12 Power Sources Item Board and/or Main Bus Normal Alternate Remarks via TR TU3A (via TR TEA)

Alternate 1 (f) Unit 3, 480-V Unit Bd 3B 4 kV unit bd 3B 4 kV com bd A via TR TU3B (via TR TEA) 19 480-V Lighting Boards (a) 480-V Lighting Bd 1 4 kV com bd A 4 kV com bd B Transfer between sources is manual via TR TL1 (via TR TEB) only. Each 480>>V lighting board serves as the power source, via single phase voltage regulators and 480-V to 240/120-V stepdown trans-formers, for three 240/120-V lighting boards per unit. These unit lighting boards serve various distribution cabinets in the plant.

(b) 480-V Lighting Bd 2 4 kV oom bd A kV com bd B via TR TL2 (via TR TEB)

(c) 480-V Lighting Bd 3 4 kV com bd B 4 kV com bd A via. TR TL3 (via TR TEA) 20 480-V Common Boards

('a) 480-V Common Bd 1 Bub A 4 kV com bd A Bus B of Item 20a Automatic transfer from the normal via TR TC1A to the alternate source is initiated Bus B 4kV com bd B Bus A of Item 20a by time-undervoltage on the normal via TR TC1B source. Return to the normal souroe is automatic upon return of voltage to the normal source.

(b) 480-V Common Bd 2 Bus A kV com bd A Bus B of Item 20b via TR TC2A Bus B 4kV com bd B Bus A of Item 20b via TR TC2B (c) 480-V Common Bd 3 Bus A 4 kV com bd A Bus B of Item 20c via TR TC3A Bus B kV com bd B Bus A of Item 20c via TR TC3B 21 480-V Service Building Main Board Bus A kV com bd A Bus B of Item 21 Same as remarks for Iten 20.

-

~ Table 8.3-1 "Auxiliary Power Supplies and Bus Transfer Schemes - Sheet 13 Power Sources Item Board and/or Main Bus Normal Alternate Remarks via TR TSBA Bus B 4,kV com bd B Bus A of Item 21 via TR TSBB 22 480-V Radwaste Boards.

Board 480-V Serv Bldg Bd (item 21) Bus A

1) 480-V com bd 1

2) 480-V Diesel Aux If the normal feed should fail, a manually aotuated transfer to the 1'oard

'Bd-A souroe may be made. 'lternate 2 480-V com bd 1 1) 480-V Serv Bldg Bd-

- Item 21 Bus B (iten 21) 2),480-V Diesel Aux Bd-B 23 480-V- Auxiliary, Boiler Bd Bus A 480-V com bd 3, 480-V com bd '1, Both buses are normally fed from Bus A Bus B source shown, and with te manually Bus B 480-V com bd 3, 480-V com bd,.1, operated .bus tie break"r closed.

Bus A Bus B Automatic transfer of both buses from the normal to the alternate source is initiated by time-under-voltage on the normal source. Return to the normal source is automatic upon return of voltage to the normal source.

24 480-V Control Bay Vent, Boards Board A 480-V shutdown Bd 1A 480-V com bd 1 Automatic Transfer from the normal Board B 480-V com Bd 3 480-V shutdown Bd 3B to the alternate source if ini-tiated by time-undervoltage on the normal source. Return to the normal souroe is automatic upon return of voltage to the normal source. The normally closed, manually operated bus tie breaker provides for main-tenance on one bus section while keeping the other bus section energixed and in operation.

25 480-V Turbine MOV Boards (a) 'nit 1, Board lA 480-V unit bd 1A 480-V con bd 1, Automatic transfer from the Bus A normal to the alternate source is initiated by time-undervoltage on the normal source. Return to the normal source is automatic upon.

return oi voltage to the normal source.

(b) Unit 1, Board 1B 480-V unit bd 1B 480 V com bd 2 Bus B

0 a

Table 8.3-1 Auxiliary Power Supplies and Bus Transfer Schenes - Sheet 14 Power Sources Iten Boar d and/or Hain Bus Homal Alternate Renarks (c) Unit 1, Board 1C 480-V unit bd 1B 480-V con bd 2-Bus B (d) Unit 2, Board

~ 2A 480-V unit bd 2A 480-V con bd 3-Bus B (e) Unit. 2, Board 2B 480-V unit bd 2B 480-V con bd 2-Bus B Unit 2, Board 2C -480-V unit bd 2B 480-V con bd 2-Bus r

A (8) Unit 3, Board 3A 480-V,unit bd 3A 480-V con bd 3-Bus A (h)

Unit 3, Board 3B 480-V unit bd 3B 480-V con bd 3-Bus B (i) Unit 3, Board 3C 480-V unit bd 38 480-V con bd 2-Bus A 26 480-V Condensate Benin-eralizer Boards (a) Unit 1 480-V unit bd 1A 480-V shdn bd 1B In case of failure of the nornal source,. autonatic transfer is cade to an energized alternate source.

Upon restoration of the nornal source, .autonatic return to nornal is effected.

(b) Unit 2 480-V unit bd 2A 480-V shdn bd 2B (c) - Unit. 3- 480-V Unit bd 3A 480-V shdn bd 3B 27 480-V Reactor Building Vent Boards (a) Unit 1, Board lA 480-V unit bd lA 480-V con bd 1-Bus B See renarks of Iten 24.

(b) Unit 1, Board.1B 480-V unit bd 1A 480-V con bd 1-Bus B (c) Unit 2, Board 2A 480-V unit bd 2A 480-V con bd 3-Bus A (d) Unit 2, Board 2B 480-V unit bd 2A 480-V con bd 3-Bus A (e) Unit 3, Board 3A 480-V unit bd 3A 480-V con bd 3-Bus B (f) Unit 3, Board 3B 480-V unit bd 3A 480-V con bd 3-Bus B 28 480-V Turbine Building Vent Boards (a) Unit 1. Board 1A 480-V unit bd, lA 480-V con bd 1-Bus A See renarks on Iten 24.

(b) Unit 1, Board 1B', 480-V unit bd 1B 480-V con bd 2-Bus B

Table 8.3-1 Auxiliary Power Supplies and Bus Transfer Schemes - Sheet 15 Power Sources Item Board and/or Main Bus Normal Alternate Remarks (c) Unit 2, Board 2A 480-V unit bd 2A 480-V corn bd 3-Bus B (d) Unit 2, Board 2B 480-V unit bd 28 480-V com bd 2-Bus A (e) Unit 3, Board 3A 480-V unit bd 3A 480-V corn bd 3-Bus A (f) Unit 3, Board 3B 480-V unit bd 3B 480-V con bd 2-Bus A 29 480-V Shutdown Boards (a) Unit 1, 480-V Shutdown Bd 1A 4 kV shutdown bd A 4 kV shutdown bd B Transfer from the normal to the via TR TS1A via TR TS1E alternate source is manual.

Interlocking is provided to prevent manually transferring to a'faulted board and to prevent paralleling two sources.

(b) Unit 1, 480-V Shutdown Bd 18 4 kV shutdown bd C 4 kV shutdown bd B Remark (a) via TR TS1B via TR TS1E (c) Unit 2, 480-V Shutdown Bd 2A 4 kV shutdown bd B kV shutdown bd C Remark (a) via TR TS2A via TR TS2E (d) Unit 2, 480-V shutdown Bd 2B 4 kV shutdown bd D 4 kV shutdown bd C Remark (a) via TR TS2B via TR TS2E (e) Unit 3, 480-V Shutdown Bd 3A 4kV shutdown bd 3EA kV shutdown bd 3EB Remark (a) via TR TS3A via TR TS3E (f) Unit 3, 480-V Shutdown Bd 3B 4 kV shutdown bd 3EC 4 kV shutdown bd 3EB Remark (a) via TR TS3B via TR TS3E 30 480-V Reactor MOV Boards Remark 29(a)

(a) Unit 1, 480-V Reac HOV Bd 1A 480-V Shutdown Bd 1A 480-V Shutdown Bd 1B Remark 29(a)

(b) Unit 1, 480-V Reac HOV bd 1B 480-V Shutdown Bd 1B 480-V Shutdown Bd 1A Remark 29(a)

(c) Unit 1, 480-V Reac HOV Bd 1C 480-V Shutdown Bd 1B 480-V Shutdown Bd 1A Remark 29(a)

(d) Unit 1, 480-V Reac MOV Bd 1D 480-V Shutdown Bd lA 480-V Shutdown Bd 1B Automatic transfer from the via MG set via HG set normal to the alternate source is initiated by time-undervoltage on the normal source. Return to the normal source is manual upon return of voltage to the normal source. Isolation between normal and alternate is provided by MG sets.

(e) Unit 1, 480-V Reac MOV Bd 1E 480-V Shutdown Bd 1B 480-V Shutdown Bd 1A Automatic transfer from the normal

~ '

0 0 Table 8 3-1 Auxiliary Power-Supplies and Bus Transfer Schemes - Sheet 16 Power Sources Item Board and/or Main Bus Normal Alternate Remarks via HG set via HG set to the alternate source'is initiated by time-undervoltage on.

the normal-source. Return to the source is manual upon return'ormal of voltage to the normal souroe.

Isolation between normal and alternate is provided by HG sets.

(f) Unit 2, 480-V Reac MOV Bd 2A 480-V Shutdown Bd 2A 480-V Shutdown Bd 2B Transfer from the normal to the alternate sour ce is manual. Inter-locks prevent transferring'a fault from one source to another and paralleling sources.

(g) 'nit 2, 480-V Reac HOV Bd 2B 480-V Shutdown Bd 28 480-V Shutdown Bd 2A Transfer from the normal to the alter-nate source is manual. Interlocks

/

prevent transferring a fault from one source to another and paralleling sources'h)

Unit 2> 480'-V Reac MOV Bd 2C 480-V Shutdown Bd 2B 480-V Shutdown Bd 2A Transfer from the normal to the alternate source is manual. Inter-locks p'revent transferring a fault from one source to another and paralleling sources.

(i) Unit 2, 480-V Reac HOV Bd 2D 480-V Shutdown Bd 2A 480-V Shutdown Bd 2B Automatic transfer from the normal to the alternate source is initiated by time-undervoltage on the normal souroe. Return .to the normal source is manual upon return of voltage to the normal source.

(3) Unit 2> 480-V Reao MOV Bd 2E 480-V Shutdown Bd 2B 480-V Shutdown Bd 2A Automatic transfer frc the normal>

to the alternate source is initiated by time-undervoltage on the normal source. Return to= the normal source is manual upon return of voltage to C

the normal source.

(k) Unit 3, 480-V Reac HOV Bd 3A 480-V Shutdown Bd 3A 480-V Shutdown Bd 3B , Transfer from the normal to the alternate source is manual. Inter-locks prevent transferring a fault from one source to another and paralleling sources.

(I) Unit 3, 480-V Reac MOV Bd 3B 480-V Shutdown Bd-3B 480-V Shutdown Bd 3A Transfer from the normal to the alternate source is manual. Inter-locks prevent transferring a fault from one souroe to another and

. 0 Table 8.3-1 Auxiliary Power Supplies and Bus Transfer Schemes - Sheet 17 Po'wer Sources Iten Board and/ot Main Bus Noraal Alter nate R k paralleling sources.

(m) Unit 3, 480-V Reac HOV Bd 3C 480-V Shutdown Bd 3B 480-V Th'td-wn Bd 3A Transfer tron the normal to the alternate source is manual. Inter-locks prevent transferring a fault from one source to another and paralleling sources.

(n) Unit 3, 480-V Reac HOV Bd 3D 480-V Shutdown Bd 3A 480-V Shutdown Bd 3B Automatic transfer from the normal to vi& MG set via MG set the alternate source is initiated by time-undervoltage on the normal source. Return to the normal source is manual upon return to voltage to the nornal source. Isolation between normal and alternate is provided by HG sets.

(o) Unit 3, 480-V Reac MOV Bd 3E 480-V Shutdown Bd 3B 480-V Shutdown Bd 3A Automatic transfer from the normal via MG set via HG set to the alternate source is initiated by time-undervoltage on the normal source. Return to the normal source is manual upon return to voltage to the normal source. Isolation between normal and alternate is provided by HG sets.

31 480-V Diesel Auxiliary Boards (a) 480-V Diesel Aux Bd A 4 kV Shutdown Bd A 4 kV Shutdown Bd B Transfer from the normal to the via TR TDA via TR TDE alternate source is manual. Inter-locks prevent transferring a fault from one source to another and paralleling sources.

(b) 480-V Diesel Aux Bd B kV Shutdown Bd D kV Shutdown Bd B Remark (a) via TR TDB via TR TDE (c) 480-V Diesel Aux Bd 3EA 480-V Shutdown Bd 3A 480-V Shutdown Bd 38 Remark (a)

(d) 480-V Diesel Aux Bd 3EB 480-V Shutdown Bd 3B 480-V Shutdown Bd 3A Remark (a)

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INTS Daalrac A>0 (to>Paar(W

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BFNP 0 8.4 ~120 Volt 8.4.1 AC Powei Power Generation Su Ob l and ective Distribution The objective of the 120-volt a-c power supply and distribution system is to supply 120-volt a-c power to all equipment and instrumentation requiring it during all mo'des .of plant operation.

8.4.2 Power Generation Desi n Basis The '120-volt a.-c power supply and distribution system shall be capable of supplying all required loads, through the use of several independent systems, depending on the continuity of power required by each load.-

8.4.8 120-volt a-c power supply and distribution is accompli. shed by three systems. These systems are:

a. 120-volt a-c Instrument and Control'ower Supply

b. Plant Preferred and Nonprefer red 120-volt a-c System

c. Unit Preferred 120-volt a-c System The 120-volt a-c power supply and distribution system and .its relation with other plant electrical systems is shown in Figure 8.4-1.

8.4.3.1 120-Volt a-c Instrument and Control Power Su l The 120-volt a-c instrument and control power supply consists of six'nstrument and control buses (two for each unit). Each bus

,

receives its normal power supply from the appropriate 480-volt shutdown board through a 480 208/120-volt a-c 30 instrumentation and control transformer and a 208-208/120-volt a-c 30 line voltage regulator. The line voltage regulator is a regulating transformer with a 1:1 turns ratio and will maintain an output voltage of 208/120-volt a-c + 1 percent for an input range of 208-volt a-c + 10 percent, -20 percent. The 120-volt a-c instrument and control power supply and loads are shown in Figure 8.4-2.

On loss of power supply to an I and C transformer, only the'ower to those I and C .loads of one, redundant channel will be lost.

I On loss of normal auxiliary p'ower, all I and C loads will lose power until the diesel generators have picked up the 480-volt 8.4-1

BFNP shutdown board loads.

8.4.3.2 Plant Preferred and Non referred a-c S stem The plant preferred and nonpreferred a-c system consists of two distribution buses as shown in Figure 8.4-2, volume 4, chapter 8 of BFNP's FSAR. The buses normally receive power from an a-c lighting board. The preferred bus has as an alternate source of power a 250-volt d-c motor-driven generator (plant preferred M-G set). The plant preferred M-G set is started on loss of voltage to the bus and automatic transfer made on presence of voltage from the generator. The M-G set will pick up all loads that do not require manual start. Plant preferred loads will lose power while the M-G set is started and transfer is made. The nonpreferred bus loads will not be picked up by the M-G set.

Transfer of the bus back to the normal power supply is manual.

8.4.3.3 Unit Preferred a-c S stem The unit preferred a-c system, for each unit, consists of a distribution bus with a M-M-G set as the primary source of supply, a backup source of supply from a M-M-G set for another unit, and an alternate source from the. appropriate unit 480-volt shutdown board through the unit preferred a-c bus transformer, as shown in Figure 8.4-3g volume f chapter 8 of BFNP s FSAR.

Each M-M-G set consists of a 480-volt a-c motor, a 250-volt d-c motor, a flywheel, and a 240/120-volt 1 0, a-c generator (all direct coupled) with the necessary controls. The unit preferred bus is normally supplied from the generator driven by the a-c motor with the flywheel. and d-c motor being driven. On loss of power to the a-c motor, the d-c motor is automatically energized with the flywheel driving the generator during the transfer period. Therefore, the unit preferred buses do not lose power at any time during loss of auxiliary power.

Each unit preferred M-M-G set has adequate capacity to supply its normal loads plus the unit preferred loads of one other unit during periods of M-M-G set maintenance. The transfer of loads from one bus to another is accompli, shed, without interruption, by synchronizing the two M-M-G sets and supplying the loads. briefly from both sources before the.set to be shutdown is disconnected.

8.4.3.4 120-Volt a-c Distribution Panels There are four control room distribution panels (circuit breaker boards) supplied by one or more of the 120-volt a-c systems.

There is one panel for each unit and one plant panel common to all units. The 120-volt a-c loads supplied from these panels are 8.4-2

BFNP

.shown in Figures 8'.7-4a, b, c, and d, volume 4, Chapter 8 of BFNP's FSAR.~

8.4.4

~ ~ =

Ins ection and Testin All equipment associated with the 120-volt a-c power supply system, except the plant preferred M-G set, will be in operation at all times.. The plant preferred M-G set and the d-c motor drives of the unit preferred M-G sets can be periodically energized to ensure operability. Inspection of all other equipment is accomplished based upon the manufacturer's instructions and sound maintenance practices.

8.4-3

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~TECCIN5ff I eer I / IVIII,VIFIIIFIFW FaIal Va aI uvI 47 Se REVISIONS BY G.E. COMPANY 4444 Ieee JIIceao JI Ie due JII.IVWae uee ~ Ie aai4<<I W Ira eeaft are cwcaeueiaeefycdw ie Iea (ar w JI 4 w ewewu ieac aeie Aeco 73I E 700 JosE cupzfoca

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~TF NEUTRAL 4LVR-LINE VOLTAGE REGULATOR ZO8/208-/ZDV 3FSOKVA I I 3POLE 3POLE ?ALE 2POLE POLE 3FOLE 2POLE 2POLE 3POLE 3POLE 2FOLE ZPOLE I POLE 3PDLE ZFOLE ZRXE I I I I I I /. 73/E700 DIVE VIVE DIAGRAM,KEYDIAGRA/d OF PLAN'TDCb J L /IVSTRUhfEA'76 CDNTROL AC SYS TEIlA Z. 73/E 7/7 ONE VIVE 0/AGRhhf Zd VOC AWERSUPPLY SYSTEhf V) 3. 73/E753 ONE VNE DIAGRAh/ UNITICKT BKR 80 9'9 ACPANELS

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~e Luo ~o C~ TN'STRUh/ENTATIDN AND CONTROL AC SYSTEhf ONE-LINE D/AGRhkf FIGURE 8.4-2 BATTERY BOARD I /NST AND CONTROL AC SYSTEM PAIVEL BATTERY BOARD 2 INST AND CONTROL AC SYSTEM PANEL

ENCLOSURE 3 SECTION 1 Response to April 8, 1980 letter from T. A. Ippolito to H. G. Parris.

SECTION 2 Response to May 9, 1980 letter from T. A. Ippolito to H. G. Parris SECTION 3 - Response to NRC staff questions based on TVA request for license amendment TVA BFNP TS 143 (reference letter L. M. Mills to H. R. Denton dated August 6, 1980)

'e

~- SECTION 1 RESPONSE TO APRIL 8, 1980,'ETTER FROM T. A. IPPOLITO TO H. G. PARRIS-

"REQUEST FOR ADDITIONAL INFORMATION ~

BROWNS FERRY UNITS 1, 2, AND 3 .

DEGRADED GRID VOLTAGE" I

Staff position (1)(f) requires that the Technical Specifications shall include limiting conditions for operation, surveillance

, requirements, trip setpoints with minimum and maximum limits,

'and allowable values for second level undervoltage monitors.

l

,Staff position 3 states the criteria for testing requirements.

Enclosure=.2 of our June 3, 1977 letter shows all the criteria

'

of staff posi.tions (1) (f) and 3 in Model Technical Specification ITS) format.

A review of your Technical Specifications reveals that the criteria

'

will not be met without changes. Please furnish proposed changes to comply with the criteria including loss-of-voltage setpoints, allowable limits and testing capabilities. These changes should

.also follow MTS format as close as possible.

0 RESPONSE

'(See proposed technica1 specifications.)

~

~

UESTION 2 Staff -position.(l)(e) states'that the voltage monitors shall be designed to satisfy the requirements of IEEE 279-1971. Confirm that your design satisfies these requirements by documenting and describing such requirements 'as (1) seismi.c and environmental qualif ication, (2) class 1E qualif ications, (3) independence, (4) redundant, (5) reliaibility, and (6) testability and others pertinent to the design.

RESPONSE

Re uirements of IEEE 279-1971 and Environmental 'eismic ualifications will be

'he voltage monitors operable under seismic conditions:

(a) Thes'e relays (I-T-E 59H) have been seismically qualified to a more severe seismic level at other plants.

than that required for Browns Ferry Nuclear Plant.

g) The Agastat relays, types E7012 and E7022, are seismically qualified for these specific applications by'ombination of seismic and circuit analysis. The analysis compared the most pessimistic s'eismic requirement imposed on the relay at their mounting locations with the relay seismic capability established by vendor-supplied test data.

/

(c) All equipment will be located above probable maximum flood level. Monitors will be mounted inside switchgear and axe designed to operate under accident conditions with temperature range from -30'C to +70'C.

2~ Class 1E ualifications All equipment is 'Ci.ass 1E. Voltage monitors for overvoltaoe ovep and undervoltage protection are ATE type 59H solid state.

s a e relays.'he relays are arranged in a two out of three logic for each voltage condition; therefore, the failure of a single t

voltage monitor will not cause the system to be inoperable. All voltage monitors will be mounted in the shutdown system switchgear which is of compatible classifications. Time delay

=relays are located in diesel generator logic panels for units 1 and 2 and in the shutdown system switchgear for unit 3. Diesel generator logic panels have compatible classification.

Overvoltage monitors and undervoltage monitors are independent from each other. Overvoltage monitors are also independent from the undervoltage monitors connected to the same phase of the 4-kV shutdown buses. These conditions apply to each of the four shutdown boards associated with units 1 and 2 and also to each of the four boards for unit 3~

4~ Redundanc of E ui ment and Controls Each 4-kV shutdown board is supplied with three overvoltage and three undervoltage monitors. Each system of three mon'itors is connected so that a single failure will not result in the loss of 0

1 the appropriate tripping function'.

5. Reliabilit of Com onents Components used to monitor degraded. grid voltage conditions have been selected to ensure voltage monitoring system operation. These components comply with the quality control and assurance requirements as set forth in 10 PER Part 50.

'

The voltage monitors on each 4-1 V shutdown board will have the capability of being tested during normal operation. Provisions will made for periodic testing of voltage monitors and timing,.relays.

l'e I

'3

0 Provide sufficient information (voltage drop analyses) to allow voltage setpoint and time delay selected will not cause spurious separation of safety buses from offsite power during all modes of plant operation (start-up, shutdown, power operation and accident

.,condition) due to automatic or manual starting of large motors, bulk or sequential loading: or, automatic transfer of electrical loads. The .analyses should include conditions when the safety buses are supplied power 'from the Unit Auxiliary Transformer, the Start-up/Reserve transformer or other available offsite connections and assuming the need for electrical power is initiated by an anticipated transient (e.g., unit trip) oi an accident, whichever presents the largest load'emand.

RESPONSE

The 4kV shutdown board degraded voltage relaying initiates. a transfer of the shutdown board to stand by onsite (diesel) power distribution system when the board steady state voltage fails to stay within a voltage range will ensure all 0 (for 8Q seconds) fed from the board.

which proper operation of safety loads The 4kV safety motors have a normal operating range of + 10% with at least a .15% voltage drop allowed on starting. The 460V safety motors are considered to have an'operating and starting range of + 10%.

The degraded s'et points for units 1 and 2 shutdown boards are 3920V + 1X and 4400V + .1.% Unit 3 degraded voltage system will have this configuration when the generator breaker and new USS XFMR are installed.

IL The relays used for this application are I.T.E. type 59H. These relays reset at a fixed percent of their pickup value. The possibility of spurious trips has been minimized by using relays with repeatability of + 1%"at their P

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In verifying the degraded voltage points acceptability an inhouse computer program (-VNEW) was used to perform the'calculations for all sources of offsite power. The 'summary, sheets for computer studies (NIMV 2, 114, 115,,116, 117 118, 119, 120, 121, 122, and 123) are attached. A minimum of one percent and a maximum of 5% steady state voltage drops in feeder cables to the 480V loads was assumed.

The effect of minimum 500kV 'switchyard voltage (465kV) was studies in NIMV 2 and 123.

Summary sheet N'Q!V 2 shows the shutdown board voltages for the unit station service transformer carrying full unit loads and the maximum load 'on one t

'

of the shutdown buses for one unit in the accident mode. Switchyard voltage is considered to be a minimum (465kV). Shutdown board steady state voltage can 'be maintained at greater than 3920V. The largest non-s safety and shutdown board motors were independently started successfully.

Summary sheet NIMV 123'hows unit. station service transformer voltages for L00A unit 1, shutdown of unit 2, with loss of the unit 2 500kV offsite power circuit. Minimum 500kV switchyard voltage (465kV) was assumed. Under these conditions, shutdown board steady state voltage can be maintained at greater than 3920V. The largest non-safety. and shutdown board motors were started successfully.

NIMV 2 and NIMV 123 show that steady state shutdown board voltage can be s

maintained at 3920V when being fed from the minimum 300kv switchyard voltage unde" maximum loading conditions.

0 Maximum shutdown board voltage can be obtained by multiplying- the maximum switchyard voltage '(550kV) by the main 'transformer voltage ratio adjusted for 2.5X boost tap 20.7 (1.025) ('00 (.9)

'

and the USS transformer ratio adjusted for 10X buck tap ( .

4160 20 '

7

); therefore, 5501@V x ( 20.7 500 (1.025) x

)

20 7 ) = 4221V (106% of 4-kV).

/

This value is within the equipment ratings of the safety system and is well within the upper degraded set point (4400V).

,Therefore, high 500kV switchyard voltage poses no problem to 4-kVsafety loads.

The following computer runs study required '16lkV switchyard voltage to maintain unit 1 and 2 shutdown board voltages at 3920V for various 16lkV source feeds.

Summary sheets NOlV 116 117 and 118 show shutdown board voltages for units 1 and 2 when supplied from the 161kV offsite power source through the bus tie board due to a manual transfer. A LOCA in'ne unit and a shutdown of the other is assumed. Depending on cooling tower switchgear load, 161kV switchyard voltage must be maintained at 162 168 kV to assure a switch-gear voltage of 3920V. In each case the largest shutdown board motor was started successfully.'n loss of the unit 3 500kV offsite power source, the shutdown boards will stay with the unit boards as they transfer to the cooling tower transformer switchgear.. If the transfer is not successful, the unit 3 shutdown boards will transfer to the bus tie board.

0 1977 NRC'UIDELINES Position 1:

Second level of under-or-overvoltage protection with a time delay item c) reads as follows:

c) The time delay selected shall be based on the following conditions:

'

(1) The allowable time delay, including margin, shall not exceed the maximum time delay that is assumed in the FSAR .

accident analyses;

~

(2) The time delay shall minimize the effect of short duration disturbances from reducing the availability of the offsite power source(s); and (3) The allowable time duration of a degraded voltage condition at all distribution system levels shall not result in failure of safety systems or components; The maximum time delay assumed in the FSAR is 10 seconds to have the diesel generator units ready to accept loads. After a time delay of l-l/2 seconds at zero volts, the diesel generator units get a signal to start.

A degraded voltage setting of l-l/2 seconds could result in starting of P

the diesel generator units on starting an RHR pump (2000 HP). This conflicts with position c) (2). Ve have therefore chosen a 4-second I

degraded voltage diesel generator"unit start setting. This will extend the time until a diesel generating unit is ready to accept load to 12-1/2 seconds. It is felt this is more desirable than spurious starts of'the diesel generating units on motor starting.

s P

Summary sheets NIHV 114'15 and 119 show the shutdown board voltages for unit 3 with LOCA load .being supplied from the 16lkV offsite power source through the unit boards.I All non-spare unit and shutdown board 4-kV motors P

were assumed to be running.'epending;on cooling tower load, 161kV switch-

>

yard voltage must be maintained at 160-166kV to assure a minimum shutdown board voltage o'f 3920V. An overload of up to 20/ was experienced on the s

\

cooling tower transformer "X" winding initially until the Operatorf removes .

cooling tower switchyard load. This is considered acceptable. In each case, the largest shutdown board motor was started successfully.

s t

Summary sheets NIMV 120 121 and 122 show the shutdown board voltages for unit 3 for LOCA load being supplied from the 161kV offsite power source.

I through the bus tie board. Depending on cooling tower switchgear load, v

161kV switchyard voltage must be kept at'160-165kV to assure a minimum shutdown board voltage of 3920V. In each case, the largest shutdown board motor'as started successfully.

As noted on the summary sheets, some shutdown board voltages go below the 3920V level as their largest motor starts. The longest expected motor starting voltage transient is approximately 4 seconds for the RHR pump.

This time is well within .the 8$ second set point for the degraded voltage relay. This would not cause a spurious trip from an offsite source.

P 1

0 J

~ ~

The diesel generators will start if the shutdown board voltage stays below 3920V for more than 4 seconds for motor'tarting but transfer to the diesels I

should not take.place.

Interties exist between units 1, 2, and 3 shutdown boards. An analysis of these circuits is'ot provided because they are used only in the long-term after a loss of offsite power for paralleling diesel generator A with DG 3A,

\

B-3B, C-3C, and D-3D. See section 8.5.4.1, pages 8.5-13 and -14 of FSAR.

Prom the analysis presented, it is concluded that the de raded volta e set-oints are valid for the 4kV safet s stem.

C 'I

'I Summary sheet NIMV 17 gives voltages associated with "worst case" 480V safety loads. The 480V shutdown board lA and reactor MOV board 1B were chosen for analysis because they are fed by the 480V transformer with the highest impendance and in turn feed the largest motors; therefore,, they represent the ".worst case" steady state and motor starting condition. The 4 kV shutdown board A voltage was set at minimum (3920V), the boards were fully loaded, and the largest motors associated with each board started successfully.* The 480V XFMR (TSIA) is set on 5% boost tap and all voltages.

are within acceptable limits. This roves the acce tabilit of the 3920V E

de raded volta e set oint for the 4kV shutdown boards. All 480V shutdown board XFMRS are set on 5% boost ta K 'I

~Control bay water chiller voltag'e (nonsafety load) was 1 volt low while starting.

I This is not considered significant due to the extreme "worst case" conditions.

n

0 Concerning the possibility of a 480V safety system overvoltage when being fed from 500-kV offsite source maximum'480V shutdown voltage i's the product of the maximum unit board voltage (4221V) and the 480V shutdown board transformer voltage ratio adjusted for 5% boost tap 480 (1.05) 4160 ere fore, ](~480105))511V(1 4$ $ V x 4160 1 18 of 460V)

Assuming 1X cable drop from the board to the load, the 460V safet motors cannot be sub ected to an overvolta e while bein su lied from the 500-kV

'offsite source. This is the. case for appioximately 95K .of the time.

Maximum 480V safety system voltage when being fed from 161-kV offsite" power source will be the product of the upper degraded voltage setting 4400V x (

'.

.(4400V) and the 480V shutdown board transformer voltage for'5 percent boost tap ('480 4160 (1.05

) = 533V (116%

Therefore of 460V).

ratio adjusted 4160 Assuming 1 percent cable drop from the board to the motor, the 460V safety motors can be subjected to a maximum of 5 percent overvoltage. To achieve this over voltage, three conditions must exist (1) The shutdown boards supplied from the 161-kV (occurs approximately 5 percent of the time)

(2) minimum loading and (3) maximum 161-kV switchyard voltage. Due to the improbability of the three conditions occuring simultaneously, this over voltage possibility is considered acceptable for the fr'equency and duration that the electrical distribution system is expected to be in the assumed configuration.

(i l

~

elle (C88 seals'ill

'v1 TENNESSEE VALLEY AUTHONITY sldrrr 62r wNacr

~D $T 0 ~I D600e 10/31/80 cddecscs sr DATS PROCRANNI MV2 ASSUMPTIONS This prograa verifies chat che unit station service transforcler fs capable of continuously carrying the load consisting of all auxil farles of one generating 1. The USS XBIR auto tap changer vill keep unit-BD IA at 4160-V steady seats unit operating at full load and thc naxfnun load on one of the tvo shutdovn buses vitb another generating unit fn the accident node 2. All 4-kV unit hoard notors are running and all 480-V XBRS are loaded to their Oh rating at 0.85 PF 500-kV SNITCHYAR6I (465-kV ASSL".!ED) Unit Board IA Unit Board IB Hain Transforner (2-Q percent Boost Tap) 4-'kV Hotors 4.0906 +3 1.7367 4.0906 +3 1.7367 480-V XFHRS .8500 ~6 .5268 1.1050 + .6848 Auto Tap Changer 4.9406 +3 2.2635 $ .19S6 +) 2.4215 Unit Station Ser52fre 28/32 INA - Prfnary XFMR (10 Perrenc Ik oat Tap) 12/16 MVA - Each Secondary

3. The folloving shutdovn board actors are running: 2 core spray, 2 RHR, 4 RHRSN. All 480-V XBIRS are loaded to their OA rating at 0.85 PF.

Unft Bos 18 4-kV Motors: 5.3841 +3 2.4549 CBO-V XFMRSc 500 MCM, 3/8

'00'1200A)

I'1.9141 +3 3.4031 7.7 ~26 ~ 2 HVA 50 RESULTS Shutdovn Board A hutdovn Board B

1. Total X vfnding load: 13.1 ~25.4'VA CS Transforner rating 12/16 HVA

2. Total y vfnding load: 5.7 ~25.0 MVA Transforner rating 12/16 HVA

3. Total XFHR load: 18.9 ~25.4i HVA Transforner rating 24/32 NVA MOTOR A.'0 BOARD VOLTACES NP START UP VOLTACE (kV) STFSDY STATE VOLT (kV)

6. 10 dl ~ 12006 1 d 7.7 6611? r 10666 MOTOR BOARn :IIITOR BOARn CCV 2250 UNIT 3.783 3-933 C. 156 4.190 94.+6 94.5 104.0 100.7 RHR 2000 S2IRUT 3.859 3. 915 4. 160 4 ~ 172 ALL RESULTS ARE UITHIN E UIPMENT RATINGS Tlllg CASE IS ACCFPTABLE DOIRI 96.5 94. I 104.0 (100.3 2000 SIICT 3.789 3.844 4 0160 4. I 72 DOVN 9C +7 92.+4 104.0 100.

3.832 3. S44 4 ~ 166 4.172 95.8 92.4 104.2 100.

(i 4-RV) (2 4.16) (2 4 kV) (X 4 16)

vva vase (c(( De&laze( TENNESSEE VALLEY AUTHORITY

- svaacr D Loveless ~ e I I/4/80 c(ucaao ev OATa PROGRAM N'IMV17 CIRCUIT The purpose of this progran is to verify nfniz(un 480-V voltages are available 4-kV Shutdovn Board A for starting and running 480-V safety loads at the ninf(a(n allovable 4-kV shut- 3920 V Assuued dovn board voltage of 3920-V (degraded voltage setting). 4 A/0> 2/0 l Included in source

/e, 75' 480 V R 'IRBtBfTS XFHR TSIA 750 KVA, E>5.94 Percent Mininun notor starting and running voltage is (5 Percent Boost Tap) 902,(460) i 414-V Assuning ~ aaxinun of 52 voltage drop in the notor feed cable. The niniz(un tt ~ h d ltr i 22 480V Shutdovn Board IA 952 (g) ~ 414-V A/0( 4/0 L R .0024 g > 436-V Control Bay Water Chillera 2/8, 90'x .0019 65 480V Reactor HOV APPROACH Core Spray Ihe circuit at the right uas analyzed for the stsrtup and nornal running of 7(0 Inboard Valve*

the largest shutdovn and reactor MOV board notor. 4-kV shutdoun board A vas chosen because this board feeds the largest 480-V - z(otors and therefore presents

• Largest Hotor on Board the "vorst case". Both boards vere fully loaded: RESULTS - Values in ( ) are nfnfnun acceptable Shutdovn Bd IA 750 kVA Q .85 PP Reac MOV Bd IB &98.8 KVA Q .85 PF START UP VOLTS STEADY STATE HP BOARD MOTOR BOARD MOTOR BOARD 480-V CONTROL BAY 205 S(IUTDOWN 413 427 455 458 WATER CHILLER BOARD A 414 414 436 480-V CORE SPRAY 40 REACTOR MOV 423 446 446 455 INBOARD VALVE BOARD IB 414 414 436 o ALL BOARD AND HOTOR VOLTAGES ARE ACCEPTABLE o ALL 480 V SHUTDOWN BOARD XIIO(S ARE PLACED ON 5Z BOOST TAP

vv>>>>>>ts ION oet It tll TEkkESBEE VALLEY AUTHORITY a>>est 0

D. Loveless a>>~ 10/80 esse>>so sv ASSUMPTIONS PIOCPA.'t NIHV114 4 115 The purpose of these prograas is to evaluate voltages associated vith vorst case 1. The 161-kV Svitchyard voltage ls 166-kV (NIW114) e 165-RV (NIWIIS) cooling tovcr transforner loading under thc folloving conditions Both cooling Tvr arc in servlcc aad are on 2-1/2 Boost Tap

2. XFNRS X (I) Both cooling tover XFMRS are available (2) LOCA - I;nit 3 3. Concerniag CT SMCR load

- running (NIW114) o All 480-V XIIIRS are loaded to their OA rating at 0.85 PF (3) 3 CT Punps/SMGR o 3 CT punps/S'MCR are running (NINV114) 2 - CT Pusps/SMGR running (NIW115) 2 CT puaps/SMGR are runaing (NIHV115)

Tho steady state afnfnua allovable shutdovn board voltage is 3920V HIHV114 'HINV115 161-kV SMITCHYARD CT 4-kV Mtrs 7.2571 +j 2.3853 4.8381 +3 1.5902 5.1000 + 3.1607 Cooling Tover Transforner Total I2.3571*+3 5.5460 9.9381 +3 4.7509 NVA (2'I Percent Boost Tsp)

4. All unit board 4-kV notors are running 4 all 480-V XFMRS arc loaded to 15 16 their OA rating.

CT Svltch car 8 CT Svitch ear C Unit Board 3C Unit Board 3A SOONCH 3/8 LR .0283  !

Unit Unit 4500' X~.0461 4.0906 +3 1.7367 Board Board 3A UB 4-kV Htrs 4.2909 +) 1.8338 UB 480V Loads 8 .8500 + .5268 Total 4.2909 +3 1.8338 4.9406 +3 2.2635 MVA Shutdovn Board 3FA 3EB 5~ All 4-kV shutdova board sotors are. running + all 48DV XIMRS are loaded to their Oh rating RI CS 4-RV Motors 4!7389 +j 2.1189 480-V Loads .6375 + .39SI 5JITClITARD BOARD ASD MOTOR VOLTAGES Total S!3764 +3 2.5140 NVA Sv 'fd STARIUP VOLTAGES (kv) STEADY STATE VOLT (kv)

MOTOR SBUTD04N SBUTDOMN LOADING RESULTS VOLT MOTOR BOARD BOARD 3.916 3. 922 NINVIIA HIW115

.'i IWI 14 166 kv RBR 3.663 3; 692 klie

91. 6 3.601 (88. 8 I. 630 97.9 3.916 7.

(94. 3 3.922 X 'Minding T Minding (15/20/25 Wh)

(15/20/25 HVA) 30.0 ~>>

13.5 ~24 27.0 11.0 4

+ 9n.n 87.3 ~4 3.630 3.915 3.922 Total (30/40/50 Wh) 43.1 ~24.2 38.0 25.0 Cs 3.617 nn,h 87, 97. 4 Q >> 1202 Overload >>>> 1082 Overload 3.666 3. 696 3. 918 3. 925 Hl!iVIIS 165 RV 94.4

91. 7 88. 9 98.0 RBR 3.6ns 3.634 3.918 3 925

+ 90.1 07.4 98. 0 4.4 Cs 3.621 3!634 3.918 3.925 90.5 87.4 98 0 94.4 (X 4-kv) (X4. 16-kv) (X4-kv) (X4. 16-kv

tVAttl t 1t91 OC$ 1 &ttl TENNESSEE VALLEY AUTHORITY 0

co899v9ts e1 D 4 class cate 11/I/80 cwctto sv PROGRA.'I NINV116 ASSUMPTIONS The purpose of this prograa is to verify the cooling tower transforner can 1. The 161-kV svitchyard voltage is 162-kV supply uaft I 4 2 shutdovn loads through the bus tie board under the tolloviag

<<oad it iona 2. The cooling tower avitchgear load is ZERO (no lift punps on)

1. Unit I LOCA9 Unit 2 shutdova 3. For each pair of shutdovn boards, the loading is 2 CS, 2 RHR's + 4 RHRSN's

2. Cooling tover Svgr load ~ Zero all 480-V XFMRS are loaded to their OA rating at 0.8$ PF SHUTDOli'N slmTDGNN RD ceD CIRCUIT 4-kV Motor Loads 5.3841 +$ 2.4548 5.3841 +J 2.4548 161-kV SNITCHYARD 480-V XFHRS 1.5300 + .9482 3.3388 9 (162-kV ASSUHED)

6. 9141 +$ 3.4030 6.9141 +3 3.4030

-

.9'8'ooling 88 7.7 7.7gZS.Z Tover 500 HCH .$ R .0283 TransforLter 6/If 450081 X~.0461

~26.2'ESULTS (ZIf Percent Roost Tap , X 15 1. Loading on the 1200A feed to the shutdovn boards is Cooling Tover 7-7 88 1129A Svitchgesr D us Tio 3.938 l9 1200A 2. Loading on the y vindiag of the CT transforner is 1$ .4 HVA (the Tmfadfng rating is 15/20/2$ )NA) 3, All voltages are vithia acceptable liaits Shutdovn Soarde C D MOTOR AND SOARD VOLTAGES IR CS STARTCP VOLTAGE (kV) STEADY STATE VOLT (kv)

MOTOR SOARD SHUT 3.657 3. 710 3. 926 3.938 91.4 (89. 2 98.2 94.7 RHR SHUT 3.596 3.648 3.926 3.938 89.9 87.7 93.2 (94.7 CS 3.636 90.9 (X 4-ILV) 3.648 87.7 (X 4. 16) 39932 (98.3)

(X 4-ILV) 38938 (94 ')

(X 4. 16)

tvA tete (tv ots (4 ) I) TENNESSEE VALLEY AUTHORITY sNtsv sum) rcf covtvvts sv 0 Loveless o((ft II / I /80 clcctto ev PROGRA.S NLcVII7 4 I lg ASSUHPTIONS The purpose of chess programs is to verify the cooling tover transformer can I. for each pair of shutdovn BOARDS. the loading is 2 CS. 2 RHR's, + 4 RHRSM'S supply unit I 6 2 shutdvon loads through the bus tie board for unit I LOCA, All 480-V XBIRS are loaded to their OA rating at 0.85 PF.

unit 2 shutdovn for the follovfng cooling tover svftchgear 4-kV loading:

SHUIDOMN BD A+D SHUTDOMN BD I. 2CT pumps/svitcbgear running (NIHV118) CCD'-kV Ihcors 5.3841 +j 2.4548 5.3841 +j 2.45CB

2. 3~ punps/svitchgear running (NIHV117) 480-V XFHRS 1.5300 + .9482 1.5300 + .9482 6.9141 +j 3.4030 6.91C +j 3.4030 CIRCUIT ~ 7.7 L26.2i ~ 7.7 g 26.2t 161 kV SMITCHYARD 2. Concerning CT Board loading Cooling Tover o All 480-V XFHRS are loaded to Chair Oh rating at 0.85 PF Transformer ~

(2!I Percent Boost Tap) 500 HCM 1 R 0283 o 3 CT pumps/Svftchgear are running (NIHV117)

X Y 6/!I 4500'j X-.OCGL 2 CT pumps/Svltchgear are running (NIHV118)

NIHV117 NIHV118 Cool fng Tover Svfcchgear D CT 4-kV Motors 7.2571 +j 2.3853 4.8381 +j 1.5902 Bua Tfe 12D571 +j 5.5460 9.9381 +j 4.7509 1200A RESULTS 64 NIHV117 Shutdovn Board. A 1. X Minding (15/20/25 MVA) 29 ~ 0 y Minding (15/20/25 HVA) 13. 5 MOTOR h!H) BOARD VOLTACES Total (30/40/50 MVA) 42. 5 37.4 PH C ai IGX Overload ea 1062 Overload SMYD STARTUP VOLT (kV) STFADY STATF, VOLT (kv P PA% VOLT BOARD H()?OR BOARD MOTOR BOARD 2. The steady state loadfng on the 1200A feed to the shucdovn board fs 3.926

'e IHV117 168 RIIR RHR SHUT DOMN SI IUT 3,647 (91.2$

3.586

3. 699

+88.9 3.637

3. 914 (97.9 3.914 94.4 3.926 7 7 HVA N(IN(((;(( yg~g~yg)

~ 1132 A HVAI (l((N(($ ; (~39lll-kV I 32A kV + DOL'N ~)I9. 7} ~87.4 97.9 (9C.4 3. All voltages are vfthfn acceptable limits

- CS 3+626 3.637 3.920 3.926 (90.7) 87.4 98.0 94.4 5 IIUT 'I. 649 3.702 3.916 3.928

!IDIVI 18 R IUI DO4".I (91. 2 (U9. 0 (97. 9 94.C 167 RHR SHUT 3.602 3.646 3.916 3.928 kv + DOMN ~90~1 87.6 97.9 4.4 CS 3.629 3 646 3 922 3.928 0.7 87. 6 98.1 94.4 (X 4-kV) (2 4 16-kV) (I 4-kV) (X 4 16-kV)

0

'va401clev oel Is nu TENNESSEE VALLEY AUTHORITY 0

svNscv D. Loveless ~ 11/2/80 el&cero sv PROCPAN NLNV119 ASSUMPTIONS The purpose of chin progran fs co evaluate voltages associated vfth vorst case l. The 161-kV Svftchyard Volcage fs 160-kV cool fdg tove'r loading under the follovfng conditions

2. The cooling cover Svftchgcar load fs cero

l. LOCA unit 3 shutdovn loads feed through the unfc boards

3. All unit board 4-kV notors are running and all 480-V Xfnrs are loaded to

2. Both cooling tove'r XIHRS are available their OA rating at 0.85 PP

3. Zero CT svftchgear load Unit BD 3C Unit BD 3A The sceady state nfnfaca shutdovn board voltage fs 392DV UB 4-kV Mtrsf 4.2908 +3 1.8337 4.D906 +) 1.7367 UB 480 V XFHRS e 161-kV SMlTCNYARD (160-kV ASSUMED) Total 4.2908 +3 1.8337 4.9405 +3 2.263S HVA

4. All 4-kV shutdovn board notors are running and tbe 480-V XPMRS are loaded to their OA rating Cooling Tover 4-kV Htrs: 4.7389 +3 2. 1189 Transformer 480V XPMRS .6375 + .3951 (2!f Percent Boost Tsp)

IS 16 CT Svftch ear 8 CT Svicch ear C Total. 5.3764 +3 2.5140 MVA L'nit I:nfc 500 MQI 6/d $ R~.0283 Board 3C Board 3A 4500'X-.0461 LOADINC RESULTS X-Minding (15/20/2S HVA) I 16.0 II24.4 MVA Y-'Nfndfng (15/20/25 HVA)I ZERO Total (30/40/50 HVA) I 16.0 I24.4 HVA Shutdovn Boards 3F NR S I"\ CKi:,all MilRD AgiMit/Ioii VOITIII'.ES STARTUP VOLTACES (kV) STEADY STATE VOLT (kV)

SLYD ~ SIIUTNMI SNUTDOMN PROC VOLT MOTOR MOTOR BOARD MOTOR BOARD 3.675 3e705 3.929 3.936 NfMV119 160-kV 'RIIR 91.8 (89. 1 (98.2 (94.6 RIIR

+ (90.3) (87.5) (98.2) (94,6)

CS 3.629 3 642 3.929 3.936 90.7 87.5 98.2 94.6 (2 4 kV) Z4 16kV) (Z 4 kV) (Z 4 ~ 16 kV)

Q C

1 Lh I R ]I u I

II g

II 77 7

I I

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t II 17 I

( I I:]

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'TVA ~ ETC (EN OES.IDTCI TENNESSEE VALLEY AUTHORITY S NEET ccwTvTED CT 0, Loveless DATE 11/2/80 cvscKED DT DATE PROGRA'.IS NINV. 120 121 122 ASSUMPTIONS The purpose ofthis prograa ls co evaluate voltages associated vlth a unit 3 l. Tvo coollag cover transforaers are In-servfce and set on 2-1/2I boost tap LOCA, vlth shutdova bo~rd loads being fed through che bus cie for the folloving CT svftchgear loads

2. All 4-kV unit board notors are running and the 480-V XFNR ls loaded co ics OA rating at 0.85 PF SINVl20c 3'uaps/Svlcchgear ruaning sl.'IV12lc 2-CT puapslgvltchgear running NivVI22I ZERO load on CT Svitchgear U.B. 4-kV Motors: 4.0906 +g 1.7367 Total 4.9406 +3 2.2635 MVA

3. All 4-kV shutdovn board notors are running (4 CS, 4 RHR, 4 RHRSV) aad all 480-V XINRS are loaded to their Oh rating at 0.85 PF Ccollng Tover Transforaer 500 MCH, 6/8 R~.0283 4-kV Hotors: 9.4719 +) 4.2378 (2II Percent Boost Tap) T 4500' .0461 6

Total 11.0079 +$ 5.1860NVA Bus Tie Cool ing IWt SvCr Unfc Board '8 Shutdovn Boards h

F 64

4. Concerning CT svltchgear loading:

3 CT 2 CT P

punps/Svitchgear are cunning (NIHV120) punps/Svltchgear are running (NINV121)

ZERO Svitchgear load (NIHV122)

S"ITCHYA~PD BOARD ASD NOTOR VOLTAGES'UI CS NIMV120 N INV121 STARTUP VOI.TAGFS ()V) STfADY STATE kV 4-kV Motors SQYD SH!:TDmm SHUTDOWN 7.2571 +3 2.3853 4.8381 +3 1.5402 480-V XFHRS I POG VOLT HOTOR BOARD MOTOR BOARD

'3, 663 3.692 3. 915 3. 921 lI'TVI20 IGS-)V RHR (91 (SS.R (97.9) (94.3 Total 12.3571 +3 5.5460 9.9381 +3 4.1509

+6 RHR 3.602 3.630 3.915 ~ 3.921 LOADING RESULTS

+ 50,~1 <87.3 9~7.9 94.3 CS 3. 617 3. 6'10 3. 914 3.921 NIMV120 NIHV121 NPIVI2 (90. 4 u7, o4 J. GAG F 695 3. 911 3 ~ 523 (88.8 X Niadlng (15/20/25 HVA) 19 0 L24.3 16.4 L25.22 5.4 ~24.6 SINV I 21 164-) V RUR (91. 7 (97.9) (94. 3 BUR 3.604 3.633 3.917 3 '23 Y Minding (15/20/25 MVA) 25,7 /24.1 23.2 L25 ~ 4 12.2 L25.22 Total (30/45/50 MVA) 44 ~ 7 39. 6 17. 6 e +90.1 87. (97, 4.

CS 3.620 3.6'13 '1. 916 3.921 0, I II1.3 2l.. 4

3. 612 3 ~ 702 3. 925 3 '31

'alvV122 I55-)V RIIR (51.8) 90. 0 (98. I 94.5 RIIR ~ 3.610 3.639 3. 925 3.931

+ ~90. 3 87.5 98. I 4 5 CS . 3.626 3+639 3,924 3+ 931 90.7 87.5 8. 4.

(I 4-kV) (I 4.16-kV) (I 4-kV) (24 ~ 16-kV)

I' tvA tttt Its ots 1 MI) TKNNKSSKK YALLKYAUTHORITY sacer D. Loveless sate tt/4/80 oats PROGRAM 'NIMV123 ASSUHPTIONS The purpose ot this progran is co evaluate voltages associated vith a unit I l. The 500-kV svttchyard voltage is a ntninun (465-kV)

LOCA, unit 2 shutdovn, and loss of unit 2's 500-kV offsite pover circuit.

2. The USS XFHR auto cap changer vill keep unit BDIA ac ~ 4160-V steady state 500-kV SMITCHYARD 3. All 4-kV unit board nocors are running and all 48DV XFN are loaded to (465-kV ASSUMED) their OA rating at 0.85 FF L'nit Board IA Unit Board IB Hain Trsnsforner (2ttI Boost Tap) 4-kV Motors 4.0906 +3 1.7367 4.0906 +3 1.7367 480-V XIIIRS Auto Tap Changer (+IOI)

Total 4 '496 +3 2 '63S S. 1956 +3 2 '215 MVA Unit Scatton Service 4. For each pair of shutdovn boards the folloving 4-kV notors are running:

Transforner (102 Boost Tap) 2 core spray, 2 RIIR, 4 RHP~. All 480-V Xlm are loaded to their OA rating ttnt t Untt Board IA Board 18 4-kV Mtrs/2 Shutdovn Bdst 5.3841 +3 2.4548 6.9141 +3 3.4030 MVA Shutdovn Boards LOADINC RESULTS RN CS 500 mt 3/tt X Minding (12/16 INA)t 13.1 MVA SOO'1200A) T ltinding (12/16 HVA) t 13.4 HVA Total (24/32 HVA)t 26.6 25 ' HVA MOICP. hbD BOARD VOLTACES SThRTUP kV STEADY STATE kV MOTOR HP BOARD MOTOR BOARD MOTOR BOARD

3. 767 4.139 4.172 2230 UNIT 94.2t 103.5 100. 3 3.843 3. 898 4. I 42 4. 154 2INO 96. I 93. 7 103. 6 99. 9 RHR 2000 3.773 3.828 4. 142 4.154

+ 4 2.0 IO't. 6 99.9 3+815 3.828 4 ~ 148 4.154

.4 2.0 0't. 7 99.9 (I 4 kV) (I 4 16-kv) (I 4 kv) (I 4 ~ 16-kv)

SECTION 2 RESPONSE TO MAY 9, 1980, LETTER FROM T. A. IPPOLITO TO H. G. PARRIS WITH ENCLOSED "QUESTIONS ON ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES"- BROWNS FERRY NUCLEAR PLANT As requested in the May 9, 1980, letter:

I Confirm .the acceptability of the voltage conditions op the station electric distribution systems with regard to both (1) potential overloading due to transfers to either safety or nonsafety loads, and (2)'otent'ial starting transient problems in addition to the concerns expressed in our June 2, 1977, correspondence with regard "to degraded voltage conditions due to conditions originating on the grid. Specifically:

UESTION 1 Figure 1 *shows that one shutdown bus (Board) can have power supplied from a second shutdown bus. Xf nothing prohibits such a connection, it should be analyzed for all three units as NRC guideline 1 requires.

REFERENCE I

1 . Separate analyses should be performed assuming the power source to

.safety buses is (a) the unit auxiliary transformer; (b) the startup transformer; and (c) other. available connections to the offsite network one by one assuming the need for electric power is initiated by (1) an anticipated tiansient (e.g., unit trip) or (2) an accident, whichever presents the largest load demand situation.

13 . Analysis documentation should include a statement of the assumptions for each case analyzed.

RESPONSE

The interties between units 1, 2, and 3 shutdown boards are used only in the long term after a loss of offsite power'See for paralleling diesel generator A with DG3A, B-3B, C-3C, and D-3D. FS'AR section 8.5:4.1, pg;8,(-13 and -14. '

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• KEY DIAGRAM IN ENCL,OSURE 2

0 c" ~uestion 2 Pith the addition of generator low-side breakers and (automatic7) tap-changing station sexvice transformers (Items 4, 5, ); another-possible power source to the Class lE buses., is established. Per NRC e this be'analyzed for all three units.

guideline 1., should

'

A Reference e

1 . Separate analyses should be performed assuming the power soux'ce to safety buses is (a) the unit auxiliary transformer; (b) the startup transformer; and (c) other available connections to the offsite network one by one assuming the need for electric power is initiated by (1) an anticipated transient (e.g., unit trip) or (2) an accident, whichever presents the largest load demand situation.

I

RESPONSE

1 and 2 shutdown buses

'nits can be supplied from either of the preferred offsite sources (500-kV or 161-kV grid). The safety system design provides for normal, power to the shutdown buses to be provided through the unit station service transformer (USST) which connects to the genex'ator bus through the main transformer to the 500-kV switchyard. If the normal source circuit to a shutdown bus is lost, the shutdown bus will automatically transfer to the alternate unit which has-its normal source connection back to'he 500-kV switch-yax'd. It would take a double failure before a shutdown bus would be powered from the 161-kV switchyard. Analysis has been made for the loads of unit 1 in LOCA and unit 2 in a full load refection (which's the worst case loading) when powered through the USST from the 500-kV switchyard. Separate analysis is

~ not provided for unit 2 USST supplying the identical analysis to that provided for unit 1.

same I

loads, since kt would be an

0 Unit 3 has been analyzed for the LOCA loading (which represents the worst case loading) when the shutdown buses are powered from the cooling tower I

transformers which provide the two preferred offsite circuits to unit 3 from the 161-kV grid. An analysis was also made for this same loading when the safety buses are powered from the 4-kV bustie board which connects I

through the cooling tower transformer to the 161-kV pre'ferred offsite I

power source.

Summary sheets for the various configurations for providing offsite power to the safety buses are included with our response to question 3 of NRC letter, Thomas A. lppolito.to H. G. Parris, Docket Nos. 50-259, 50-260, and 50-296 dated April 8, 1980, Request for Additional Information Degraded Grid Voltage. The summary sheets for each configuration show the connection to the offsite power system that is analyzed, the assumptions made and the results of the computer-assisted analysis.

uestion

3. Supply the calculated voltages for all low-voltage AC (480V and less),

Class lE buses (including alternate source connections) for each analyzed case. Do these systems supply any instruments and control circuits as required by GDC 13? If so, is all I

equipment rated to I

opeiate with the analyzed voltages wihout blowing .fuses, overheating, etc., and w'ithout affecting the equipments'bility to perform the required function?

RESPONSE

For voltages at the 480V buses, see the response to questions 3 of the April 8, 1980, request for additional information. The voltage'as calculated for the buses with the worst case loads, and largest motors, and proved adequate for all safety loads; thus other buses with lesser loads, smaller motors, and shorter feeder cables are assumed to be adequate.

The pickup voltage 'for the 480V MCC starters and contactors is. 85 percent of rated 120 volts, or 102 volts. The dropout voltage for the 480V MCC starters and contactors is 60 percent of rated 120 volts, or 72 volts.

The fuse sizes used on the control power transformer secondaries are I

I selected to prevent blowing fuses. Data used:

Amps fuse can carry Starter Pickup for 8.5 sec. (degraded VA 'mps at Transformer Size- Fuse Size volta e timeout 85X 75va FRN 0.8 4.8 145 1.42 ~

150va FRN 1.6 9.5 '530 5. 196, 200va FRN 2.5 14 1050 10.29 300va FRN 3.2 20 1150 11.27 The fuses used were recommended by the MCC mfr to protect tRe control, 1

power transformers. The inrush volt-amperes to pick up moto starter

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and contactors will produce a current less than that required to blow the fuses during the 8.5 seconds allowed before transferring to the diesel generators due to degraded secondary voltage.

Allowing 5 percent voltage drop in control circuits will maintain a voltage well above the motor starter or contractor dropout voltage.

The starters and contactors will not overheat during the 8.5 seconds before transferring to the diesel generators should a degraded voltage occur.

An analysis of the Instrument and Control (I&C) system was performed, and it was determined that the automatic alternate source connections must be removed due to excessive loading on the I&C transformers supplying this system. These connections have been disabled. It was also determined that the Class 1E instrument and control power systems (I&C) would not operate properly during degraded voltage conditions (less than 3920 volts) due to the lack of voltage regulation in the Class 1E I&C buses.

However, modifications on the Class 1E I&C system cannot be implemented during the units 1 and 2 outage scheduled to begin April 15, 1981.

Therefore, in the interim period the I&C system will remain in its present configuration, with the auxiliary power system's degraded voltage limit maintained at the existing limit (3,920 volts) to ensure proper system operation. This modification will be implemented on the Class 1E I&C power system on units 1 and 2 at their next refueling outage.

The modifications in the I&C system to be implemented will be replacement of the present non-regulating, 30-kVA, 480/208-120-V transformers (2 per unit) by 75-kVA, 'F80/208-120-V transformers and 208-120Y/208-120Y line voltage regulators (1,per bus, 2 per unit), (see attachment 1).

Based on these modifications,'he I&C bus voltages were calculated.

4 The bus voltage calculations were performed assuming the line voltage regulators (LVR's) will have an output,'s specified by the manufacturer, of 208-V + 1 percent, for an input voltage range of"208-V + 10 percent,

-20 percent. The load currents used for maximum load and maximum voltage drops through the cables were determined by using manufacturer's specifications.

The worst case loading was first'examined to determine the minimum voltage of all four I&C buses (2 per unit); Oith worst case loading determined by manufacturers'pecifications, the minimum voltage that occurred at the I&C buses was 205V 1 line-to-line. The maximum voltage at the I&C buses was determined by evaluating the syst: em with minimum loading. The minimum load used was no-load and therefore, no voltage drop was considered in the cables. The maximum voltage possible at the I&C buses was 210-V line-to-line.

All equipment required by GDC 13 connected to the I&C buses was rated to operate within these voltage levels given without inhibiting the function of the equipment.

As indicated before, the output of the LVR was assumed to be 208V + 1 percent.

In order to assure this output of the LVR, the input must range between 166.4V to 228.8V (+10 percent, -20 percent). In order to insure this range (166.4-228.8), the 480volt supply boards must not fluctuate outside the following limits: 400-volts to 528-volts.

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uestion 4~ The ENGINEERED SAFETY FEATURE ACTUATION SYSTEM INSTRUMENTATION TRIP b

VALUES, table shows that a +5 percent tolerance is allowed oa 3920V b

(95 percent of 4160V)'set point (figure 1 ). Positive 5 percent tolerance will cause spurious trip of offsite power (NRC Guideline h

12 ) whereas the negative 5 percent tolerance will cause unacceptable h

voltages on equipment on 480V and below (NRC guidelines 10 ). Justify the proposed tolerance band or provide new values.

h w

. References h

e 0 10 . For each. case evaluated the calculated voltages on each safety bus should be compared with the voltage-time settings voltage relays on these safety buses. Any for the under-identified inadequacies in under-voltage relay settings require immediate remedial action and notifi'cation of NRC.

C 12 . Voltage-time settipgs for undervoltage relays shall be selected so as to avoid spurious separation of safety buses from

/

offsite power during plant startup, normal operation and shutdown due to startup and/or k

operation of electric loads.

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RESPONSE

Units 1 and 2 will have a new degraded voltage scheme installed during the Spring 1981 outage when the new unit station service transformers are added to both units. For details of the degraded voltage operation on units 1 and 2; see 'the response to question 3 of the April 8, 1980, NRC request for additional information.

The +5 percent tolerance for the degraded voltage relays is not a setting tolerance. The relays are set to pick up at 3920V. The +5 percent tolerance is the relay manufacturers expected operating toierance for the life of the relay. TVA expects through testing, recalibiation, and maintenance, if necessary, to get deviations in relay operation of less than the +5 percent variation from the relay setpoint.'he relays have been installed and there have, been no spurious trips from the offsite power source due to degraded voltage relay operation. (The +5 percent tolerance will be reduced to al percent when the new degraded voltage relays are installed during the spring 1981 outage).

guestinn

5. The TVA rcfercnces do not define the minimiim.and maximum anticipated grid voltages. Guideline 6 allows three methods of determining the I

value of the degraded grid vol tagc, whichever provides the wor"'c case.

I TVA shoujd dcscri l>u how their grid voltage'cvcls are dctcnnincit (nnc

~ method may produce thc low voltage while another method may produce

(

the high voltage) and state what these values are.

Rcfcrcnce e

6 . The voltage at the terminals of each'safety load should be calculat:ed based on thc above listed considerations and assumptions and based on the assumption that the grid voltage i.s at the "minimum expected value." The "mimjnum expected. value'hould be selected based on the least of the following:

The minimum steady-state voltage experienced at the connection to the offsite circuit.

vol t age cxpcc ted t the connccL ion to thc -o ffs j t.e I'.

The minimum a circuit du< ~

to cont.ingcncy plans which may result. in reduced 0 voltage frnm this grid.

Co The minimum prcdictcd grid voltage from grid stability analysis (c.g., load flow st.udics).

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In the report to NRC on this matter, the licensee should state planned actions, including any proposed "Limiting Conditions for Operation" for Technical Specifications, in response to experiencing voltage at'he connection to the offsite circuit which is less than the "minimum expected value."

R~es esse The 500kV minimum grid voltage will be 465kV (93 percent of 500kV) based on co'ntingency plans. The 500kV grid maximum voltage will be 550kV (110 percen of 500kV) based on contingency plans.

'The 161-kV grid minimum voltage will be 160 kV (99.4 percent of 161-kV) based on grid stability analysis. The 161-kV grid maximum voltage will be 170-kV (105.6 percent of 161-kV) based on the contingency of loss of the Trinity 161-kV line.

The setpoint to trip the safety loads is based on an analysis at the 4-kV shutdown boards when these boards are carrying the worst case loads.

The trip point is not based on the 161-kV or 500-kV grid voltage, and the boards will not trip and transfer to the diesel generator due to a s

grid voltage. The 161-kV grid voltage is annunciated to make the operator aware that the grid is reaching a point where under worst case conditions, the voltage might be less than desirable.

0

~ 5 uestion e effect of starting and running

6. Per NRC guidelines 3 and 9 , compare the a 8000-HP reactor recirc. M-G set on al'l class 1E buses and loads with 4

the',required voltage range for normal operation of the'se class 1E loads (starters, contactors, motor ratings, .etc.). What are the bus and load voltages when starting the largest 480V class 1E. load when all class 1E, buses are otherwise fully loaded'eferences 3 . ~

All actions .the electric power system is designed to automatically initiate 'should be assumed to occur as designed (e.g., automatic bulk or sequential loading or automatic transfers of bulk loads from one transformer to another). Included should be consideration of starting of large non-safety loads (e.g., condensate pumps).

9 . The calculated voltages at the terminals of each safety load should be compared with the required voltage range for normal operation and starting of that load. Any identified inadequacies of calculated voltage require immediate 'remedial action and notification of NRC.

R~es onse The 8000-HP reactor recirc., M-G set is powered from a separate Station Service Transformer .SST winding and will have no effect .on the voltages to the C1ass 1E buses.

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For bus and load voltages when starting the largest 480V Class 1E load when all Class 1E buses are fully loaded, see the response to question 3 of the April 8, 1980, request for additional information.

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guestion e

7. NRC guideline IIe , which asks for a determination of the maximum voltage expected at each safety load (and starting circuit), has not s

'I been supplied by any of the TVA references. TVA should supply this I.

analysis; they should identify and correct any overvoltage conditions.

Reference ll . To provide assurance that actions taken to assure adequate voltage levels for safety loads do not result in excessive voltage, assuming the maximum expected value of voltage at the connection to the offsite circuit, a determination should be made of the maximum voltage expected at the terminals of each safety load and its starting circuit, If this voltage exceeds the maximum voltage rating of any item of safety equipment immediate remedial action is required and NRC shall be

~ notified. L

~Res onse I

Sec the response to question 3 of the April 8, 1980 request for additional information. on TttItw,'s no load analysts which hqs to be the worst .case for a high voltage condition.

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0 guestion S. The TVA references have not provided a separate analysis for each Browns Ferry unit as required by NRC guideline 2 . TVA should supply

'the analysis of the minimum grid condition and the "largest load demand situation" for each unit, and include the documentation required by NRC guideline 7 References e

2 . For multi-unit stations a separate analysis should be performed for each unit assuming (l),an ac'cident in the unit being analyzed and simultaneous shutdown of all other units at that station; or (2) an

'

anticipated transient in the unit being analyzed (e.g., unit trip) and simultaneous shutdown of all other units at that station, whichever presents the largest load demand situation.

e 7 . The voltage analysis should include documentation for each condition analyzed, of the voltage at the 'input and output of each transformer and at each intermediate bus between'the connection to the offsite circuit and the terminals of each safety load.,

~Res onse Sec response to question 2 in this series of questions.

~ ~

uestion e

9. The NRC requires (page 2, paragraph 3 ) verification of the analysis method and parameters. Th8TVA should submit (a) "a description of the method for performing this verification, and (b) the test results,"

as the referenced submittals did not cover this material.

Reference e

3 . The adequacy of the onsite distribution of power from the offsite circuits shall be verified by test to assure that analysis results are valid. Please provide: (1) a description of the method for performing this verification, and (2) the test results. If previous tests verify the results of the analysis, then test results should be submitted and additional tests need not be performed.

R~es onse TVA's analysis is based on worst case conditions such as loss of coolant accident and/or full load rejection with transmission grid voltage extremes.

These conditions and events cannot be established for test. We propose to verify the analysis and design adequacy as required in the staff position by the following method:

0, 0'

At a given time, the configuration for a specified part of the auxiliary power system will be recorded along with data (current, voltage, kilowatts, and running motors) taken at specified medium and low voltage boards, and applicable grid and/or generator voltage. Using this information, along with manufacturer's data for motors, transformers, etc., voltages'ill

'be calculated for the above boards using the same Computer-assisted methods as used in the worst case conditions calculations. Acceptance criteria for comparing the calculated voltages with measured voltages will be established after test accuracy of meters is established and before calculations are made. Once the calculation methods are verified by comparison to test data within the acceptance criteria, calculations performed previously by the same methods to predict operating voltages for other conditions, loadings, or configurations of the auxiliary power system will be considered valid.

The tests will be performed and verification of the analysis method and parameters will be submitted after installation of the generator breakers and new unit station service transformers.

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~ '4 uestioa I 10. The HRC requested (page 2, paragraph 4 ) that the TVA review the N

Browns Fe'rry,electric power systems to determine if potential I

violations of GDC 17 existed. The TVA references did not contain the 1

requested review. The TVA should supply the requested review.

Reference Paragraph 4, page 2 from NRC generic letter to all Power Reactor Licensees, "Adequacy of Station Electric Distribution System Voltages" reads as follows:

0 In, addition, you.are requested to review the your nuclear station to determine if there electric power systems of are any events or conditions which could result in the simultaneous or consequential .loss of both required circuits to the offsite network to determine if any potential exists for violation of GDC-17 in this regard. These reviews should'e completed, and a copy of the analyses'provided to NRC within/

60 days of the date of this letter.

~Res onse The electric power distribution system has been reviewed for potential violation of GOC-17, and TVA's conclusion is that all requirements are met.

In the process of this review we did find that the 250-volt dc power for both the 500-kV switchyard equipment (power circuit breaker control) and f line

0 relaying and thel61-kV switchyard equipment is supplied from the same battery board. (When the undervoltage modification is installed, the 500-kY system will be on offsite source and the 161-kV system, the other. source.)

This battery board has access to two separate and'independent batteries through a manual transfer switch., It. should be pointed out that in the event the battery board is lost, the status of either offsite circuit is not affected.

Our current practice is to provide separate dc supplies for each offsite power circuit. A second 250 Vdc plant battery is to be installed within

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the next two years,and the 161-kV switchyard and line relaying will be transferred to this new battery system.

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REFERENCES I

TVA letter J.E. Gil1 eland to Edson G. Case, Office of Nuclear Reactor Regulation, NRC, Docket Nos. 50-259, -260, -296, dated May 2, 1978.

TVA letter J. E. Gilleland to Director of Nuclear Reactor Regulation, NRC, Docket Nos. 50-259, -260, -296, dated May 12, 1978.

cd TVA letter R..H. Davidson to 'Edson G. Case, Office of Nuclear Reactor Regulation, NRC, Docket Nos. 50-259, -260, -296; dated May 17, 1978.

TVA letter.H. S. Fox to J. P. O'Reilly, Office of Inspection and Enforcement, Region II, NRC, Docket No. 50-259, dated January 25, 1979.

NRC generic letter to All Pover Reactor Licensees, "Adequacy of Station Electric Distribution I System Voltage." dated August 8, 1979.

TVA letter L. M. Mills to Director of Nuclear Reactor Regulation,,

NRC, Docket Nos. 50-259, -260, -796, dated September 4, 1979.

~ ~

SECTION 3 RESPONSE TO NRC STAFF QUESTIONS FROM REVIEW OF TVA REQUEST FOR LICENSE AMENDMENT TVA BFNP TS 143 (Reference TVA letter from L.N.Mills to H.R.Denton dated August 6, 1980)

Pa e 1 uestion 1

.In Enclosure 1, Table 4.9.A.4.c, "Voltage Relay Setpoints," for the second-level undervoltage sensing relays, an allowable time delay is not given. What is it? The same listing shows an overlap between the trip setpoint and reset setpoint. Discuss, primarily, is it possible for the reset level to be below the trip level or is the reset set-point a fixed (plus tolerance) percent above the trip setpoint?

Response

The degraded setpoints for units 1 and 2 shutdown boards are 3920V + 1%

and 4400V + 1%. The relays used for this application are I.T.E. type 59H.

The characteristics of these relays are such that the dropout and reset times are "instantaneous." These relays are not provided with any type of adjustable time-delay feature. Additional time delay, when required, is provided by auxiliary time-delay relays. Verification of these time-delay functions will be made during the performance of existing surveillance instructions.

These relays reset at a fixed percent of their pickup value. The reset setpoint on these relays is a fixed (plus tolerance) percent above the trip setpoint. The possibility of spurious trips has been minimized by using relays with repeatability of + 1 percent at their setpoint.

Pa e 1 uestion 2 Enclosure 3, section 1, NIMV20, uses 160kV as the lowest 161kV switch-yard voltage, which produces a voltage at the shutdown board of 3782V for the steady-state condition. Since the second-level undervoltage relay trips up to a level of 3845V, it appears some voltage correction is needed to prevent spurious trips of'offsite power to the shutdown boards. GDC 17 requires that the probability of losing this second source of power be minimized. Note that, in the other steady-state studies, the same potential problem exists and also requires correction.

Response

Units 1 and 2 shutdown buses can be supplied from either of the preferred offsite sources (500-kV or 161-kV grid). The safety system design provides for. normal power to the shutdown buses to be provided through the unit station-service transformer (USST) which connects to the generator bus through the main transformer to the 500-kV switchyard. If the normal source circuit to a shutdown bus is lost, the shutdown bus will automatically transfer to the alternate unit which has its normal source connection back to the 500-kV switchyard. It would take a double failure before a shutdown bus would be powered from the 161-kV switchyard.

Analysis has been made for the loads of unit 1 in T.OCA and unit 2 in a full-load rejection (which is the worst-case loading) when powered through the USST from the 500-kV switchyard. Separate analysis is not provided for unit 2 USST supplying the same loads, since it would be an identical analysis to that provided for unit l.

Unit 3 has been analyzed for the LOCA loading (which respresents the worst-case loading) when the shutdown buses are powered from the cooling tower transformers which provide the two preferred offsite circuits to unit 3 from the 161-kV grid. An analysis was also made for this same loading when the safety buses are powered from the 4-kV,bus-tie board which connects through the cooling tower transformer to the 161-kV preferred offsite power source.

The 4-kV shutdown board degraded voltage relaying initiates a transfer of the shutdown .board to standby onsite (diesel) power distribution system when the board steady-state voltage fails to stay within a voltage range (for 8-4 seconds) which will.ensure proper operation of all safety loads fed from the board.

The 4-kV safety motors have a normal operating range of + 10 percent with at least a 15-percent voltage drop allowed on starting. The 460-V safety motors are considered to have an operating and starting range of

+ 10 percent.

The degraded setpoints for units 1 and 2 shutdown boards are 3,920 V +

one percent and 4,400 + one percent. The possibility of spurious trips has been minimized by using relays with repeatability of + one percent at their setpoint.

In verifying the degraded voltage points acceptability, an inhouse computer program (-VNEW) was used to perform the calculations for all sources of offsite power. The summary sheets for computer studies (NIMV 2, 114, 115, 116, 117, 118, 119, 120, 121,. 122, and 123) are attached.

A minimum of one percent and a maximum of five percent steady-state voltage drops in feeder cables to the 480-V loads was assumed.

The effect of minimum 500-kV switchyard voltage (465 kV) was studied in NIMV 2 and 123.

sheet NIMV

'ummary 2 shows the shutdown board voltages for the USST carrying full unit loads and the maximum load on one of the shutdown buses for one unit in the accident mode. Switchyard voltage is considered to be a minimum (465 kV). Shutdown board steady-state voltage can be maintained at greater than 3920 V. The largest nonsafety and shutdown board motors were independently started successfully.

Summary sheet NIMV 123 shows USST voltages for LOCA unit 1, shutdown of unit 2, with loss of the unit 2 500-kV offsite power circuit. Minimum 500-kV switchyard voltage (465 kV) was assumed. Under these conditions, shutdown board steady-state voltage can be maintained at greater than 3920 V. The largest nonsafety and shutdown board motors were started successfully.

NIMV 2 and NIMV 123 show that steady-state shutdown board voltage can be maintained at 3920 V when being fed from the minimum 500-kV switchyard voltage under maximum loading conditions.

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Maximum shutdown board voltage can be obtained by multiplying the maximum switchyard voltage (550kV) by the main transformer voltage ratio adjusted

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(1.025) and the USST ratio adjusted

'500 for 10 percent buck tap ( 4160 (.9) ); therefore, 500 kV x ( 20. 7 (1.025) x 2 07 500 )

( ) = 4221 V (106% of 4kV).

This value is within the equipment ratings of the safety system and is well within the upper degraded setpoint (4,400 V).

Therefore, high 500-kV switchyard voltage poses no problem to 4-kV safety loads.

The following computer runs study required 161-kV switchyard voltage to maintain unit 1 and 2 shutdown board voltages at 3,920-V for various 161-kV source feeds.

Summary sheets NIMV 116 117 and 118 show shutdown board voltages for units 1 and 2 when supplied from the 161-kV offsite power source through the bus-tie board because of a manual transfer. A LOCA. in one unit and a shutdown of the other is assumed. Depending on cooling tower switchgear load, 161-kV switchyard voltage must be maintained at 162 to 168kV to assure a swltchgear voltage of 2 920 V. Xn each case the largest shutdown board motor was started successfully.

On loss of the unit 3 500-kV offsite power source, the shutdown boards will stay with the unit board's as they transfer to the cooling tower transformer switchgear. If the transfer is not successful, the unit 3 shutdown boards will transfer to the bus-tie board.

1977 NRC GUIDELINES Position 1:

Second level of undervoltage or overvoltage protection with a time delay (item c) reads as follows:

c. The time delay selected shall be based on the following conditions:

(1) The allowable time delay, Including margin, shall not exceed the maximum time delay that is assumed in the FSAR accident analyses; (2) the time delay shall minimize the effect of short duration disturbances from reducing the availability of the offsite power source(s); and (3) the allowable time duration of a degraded voltage condition at all distribution system levels shall not result in failure of safety systems or components.

The maximum time delay assumed in the FSAR is 10 seconds to have the diesel-generator units ready to accept loads. After a time delay of

l-l/2 seconds at zero volts, the diesel generator units get a signal to start. The degraded voltage setting of 1-1/2 seconds could result in starting of the diesel-generator units on starting an RHR pump (2,000 hp).

This conflicts with position c (2). We have therefore chosen a 4-second degraded voltage diesel-generator unit start setting. This will extend the time until a diesel generating unit is ready to accept load to 12-1/2 seconds. It is felt this is more desirable than spurious sta'rts of the diesel-generator units on motor starting.

Summary sheets NIMV 114 115 and 119 show the shutdown board voltages for unit 3 with LOCA load being supplied from the 161-kV offsite power source through the unit boards. All nonspare unit and shutdown board 4-kV motors were assumed to be running. Depending on cooling tower load,

- 161-kV switchyard voltage must be maintained at 160- to 166-kV to assure a minimum shutdown board voltage of 3 920 V. An overload of up to 20 percent was experienced on the cooling tower transfer "Xu winding initially until the operator removes cooling tower switchyard load. This is considered acceptable.'n each case, the largest shutdown board motor was started successfully.

Summary sheets NIMV 120 121 and 122 show the shutdown board voltages for unit 3 for LOCA load being supplied from the 161-kV offsite power source through the bus-tie board. Depending on cooling tower switchgear load, 161-kV switchyard voltage must be kept at 160- to 165 kV to assure a minimum shutdown board voltage of 3 920 V. In each case, the largest shutdown board motor was started successfully.

As noted on the summary sheets, some shutdown board voltages go below the 3,920 V level as their largest motor starts. The longest expected motor starting voltage transient is approximately 4 seconds for RHR pump. This time is well within the 8-Q second setpoint for the degraded voltage relay.'his would not cause a spurious trip from an offsite source. The diesel generators will start if the shutdown board voltage stays below 3,920 V for more than 4 seconds for motor starting, but transfer to the diesels should not take place. From the analyses presented, i,t is concluded that the de raded volta e set pints are valid for the 4-kV safet s stems.

Pa e 1 uestion 3 Enclosure 3, section 1, provides studies (NIMV 16, 17, and 18) which show that the 4,160/480-V transformers need to use the five percent boost tap to provide adequate starting voltages for the'480-V buses.

This setting contributes to overvoltage conditions on the 480-V buses in a minimum load, high-gr'id voltage (110.9 percent when the grid voltage is 116.5 kV, 113.3 percent when the grid voltage is 170-kV) (study NIMV 15A and 17A).

Discuss the TVA plans to prevent this overvoltage condi.tion while correcting the inadequate starting voltage problem.

Response

Summary sheet NIMV 17 gives voltages associated with "worst-case" 480-V safety loads. 'he 480-V shutdown board 1A and reactor MOV board 1B were

chosen for analysis because they are fed by the 480-V transformer with the highest impendance and in turn feed the largest motors; therefore, they represent the "worst-case" steady-state and motor starting condition.

The 4-kV shutdown board A voltage was set at minimum (3,920 V), the boards were fully loaded, and the largest motors associated with each board started successfully.* The 480-V XFMR (TSIA) is set on five percent boost tap and all voltages are within acceptable limits. This roves the acce tabilit of the 3 920 V de raded volta e set oint for the 4-kV shutdown boards. All 480-V shutdown board XFMRS are set on five ercent boost ta Concerning the possiblity of a 480-V safety system overvoltage when being fed from 500-kV offsite source maximum 480-V shutdown voltage is the product of the maximum unit board voltage (4,221 V) and the 480-V shutdown board transformer voltage ratio adjusted for five percent boost Assuming one percent cable drop from the board to the load, the 460-V safet motors cannot be sub'ected to an overvolta e while bein su lied from the 500-kV offsite source. This is the case for approximately 95 percent of the time.

Maximum 480-V safety sy'tem voltage when being fed from 161-kV offsite power source will be the-product of the upper degraded voltage setting (4,400 V) and the 480-V shutdown board transformer voltage ratio adjusted for five percent boost tap 480 (1.05) Therefore,

( 4 160 )

4,400 V x ( ~~~~~ ) = 533 V (116% of 460 V).

Assuming one percent cable drop from the board to the motor, the 460-V safety motors can be subjected to a maximum of five percent overvoltage.

To achieve this overvoltage, three conditions must exist: (1) The shutdown boards supplied from the 161-kV (occurs approximately five percent of the time) (2) minimum loading, and (3) maximum 161-kV switchyard voltage. Because of the improbability of the three conditions occuring simultaneously, this overvoltage possibility is considered acceptable for the frequency and duration that the electrical distribution system is expected to be in the assumed configuration.

Pa e 1 uestion 4 , section 1, page 7, indicates that the minimum degraded voltage relay pickup time plus time delay will be approximately 8 1/2 seconds. What is the duration of the longest expected motor starting voltage transient that could operate the trip (3845V)? Will this cause a transfer to diesel power?

Response

Refer to page 1, question 2 response.

• Control bay water chiller voltage (nonsafety load) was one volt low while starting. This is not considered significant because of the extreme "worst-case" conditions.

Pa e 1 uestion 5a , Section 2:

a. The analysis requested for where shutdown board interties are used (for example, shutdown board D to shutdown board 3ED) was not provided. Provide.

Response

Interties exist between units 1, 2, and 3 shutdown boards. An analysis of these circuits is not provided because they are used only in the longterm after a loss of offsite power for paralleling diesel-generator (dg) A with dg's 3A, B-3B, C-3C, and D-3D. See section 8.5.4.1, pages 8.5-13 and -14 of FSAR.

Pa e 1 uestion 5b

b. When will the analy'sis for voltages of less then 480V be submitted7

Response

The analysis for voltages of less than 480 volts is presented below.

The pickup voltage for the 480-volt MCC starters and contactors is 85 percent of rated 120 volts, or 102 volts. The dropout voltage for the 480-volt MCC starters and contactors is 60 percent of rated 120 volts, or 72 volts.

The fuse sizes used on the control power transformer secondaries are selected to prevent blowing fuses. Data used:

Amps fuse can carry 'tarter Pickup for 8. 5 sec. (degraded VA Amps at Transformer Size Fuse Size volta e timeout) 85%

75va FRN 0.8 4.8 145 1.42 150va FRN 1;6 9.5 530 5. 196 200va FRN 2.5 14 1,050 10.29 300va FRN 3.2 20 1,150 11.27 The fuses used were recommended by the MCC manufacturer to protect the control power transformers. The inrush volt-amperes to pick up motor starter and contactors will produce a current less than that required to blow the fuses during the 8.5 seconds allowed before transferring to the diesel generators because of degraded secondary voltage.

Allowing five-percent voltage drop in control circuits will maintain a voltage well above the motor starter or contactor dropout voltage.

The starters and contactors will not overheat during the 8. 5 seconds before transferring to the diesel generators should a degraded voltage occur.

An analysis of the Instrument and Control (I&C) system,was performed, and it was determined that the automatic alternate source connections must be removed because of excessive loading on the I&C transformers

supplying this system. These connections have been disabled. It was also determined that the class 1E instrument and control power systems (I&C) would not operate properly during degraded voltage conditions (less than 3,920 volts) because of the lack of voltage regulation in the class lE I&C buses.

However, modifications on the class 1E I&C systems cannot be implemented during the units 1 and 2 outage scheduled to begin April 15, 1981.

Therefore, in the interim period t'e I&C system will remain in its present configuration, with the auxiliary power system's degraded voltage limit maint6ined at the existing limit (3,920 volts) to ensure proper system operation. This modification will be implemented on the class lE I&C power system on units 1 and 2 at their next refueling outage.

'I The modifications in the I&C system to be implemented will be replacement of the present non-regulating, 30-kVA, 480/208- to 120-V transformers (2 per unit) by 75-kVA, 480/208- to 120-V transformers and 208- to 120Y/208-to 120Y line voltage regulators (1 per bus, 2 per unit). Based on these modifications, the I&C bus voltages were calculated. The bus voltage calculations were performed, assuming the line voltage regulators (LVR's) will have an output, as specified by the manufacturer, of 208-V + 1 percent, for an input voltage range of 208-V + 10 percent, -20 percent.

The load currents used for maximum load and maximum voltage drops through the cables were determined by using manufacturer's specifications.

The worst-case loading was first examined to determine the minimum voltage of all four I&C buses (2 per unit). With worst-case loading determined by manufacturers'pecifications, the minimum voltage that occurred at the I&C buses was 205 V line-to-line. The maximum voltage at the I&C buses was determined by evaluating the system with minimum loading. The minimum load used was no-load and; therefore, no voltage drop was considered in the cables. The maximum voltage possible at the I&C buses was 210-V line-to-'line.

All .equipment required by GDC 13 connected to the I&C buses was rated to operate within these voltage levels given without inhibiting the function of the equipment.

As indicated before, the output of the LVR was assumed to be 208 V + 1 percent. In order to assure this output of the LVR, the input must range between 166.4 to 228.8 V (+10 percent, -20 percent). In order to ensure this range (166.4 to 228.8), the 480-volt supply boards must not fluctuate outside the following limits: 400 to 528 volts.

Pa e 2 uestion 5c Supply the minimum load/high voltage analysis for the 500kV source as required by the NRC (August 3, 1979 letter).

Response

Refer to page 1, question 2-response.

0 Pa e 2 uestion 5d What are the equivalent voltages (500kV nominal) when using the on-load tap changing of the unit station service, transformers (grid voltage varies between 465kV /93%/ and 550kV /110%/)? Are these equivalent voltages bounded by the analysis-assumed voltage of 490kV (98%) and the voltage analysis to be provided in c, above?

Response

Refer to page 1, question 2 response.

Pa e 2 uestion 5e Per NRC quideline 3 (August 8, 1979 letter), what are the analysis results when starting the largest nonsafety load that affects the voltage on the shutdown buses?

Response

Refer to page 1, question 3 response.

Pa e 2 uestion 6 What are the pickup and dropout voltages of the 480V MCC starters and contactors (120V AC circuit)? Can these devices withstand the analyzed voltages without overheating, blowing fuses, or dropping out?

Response

Refer to page 1, question 5b response.

Pa e 3 uestion 1 It is stated that, for Unit 3, a minimum voltage of 160kV must be maintained to have adequate voltage at the 4160V shutdown boards. What are the voltages at the 480V buses and motors at this voltage?

Response

Refer to page 1, question 3 response.

Pa e 3 uestion 2 In Enclosure 3, section', NIMV 15, the minimum 16lkV voltage is stated as being 157.78kV. In Enclosure 3, section 2, page 9, it is stated as being minimum at 160kV. Has the voltage ever been below 160kV? If so, how often, when, and for what duration?

l

Response

Capacitor banks of 41 MVAR and 39 MVAR were added to the 161-kV switchyard at Browns Ferry Nuclear Plant during the spring of 1978. Since that time, the voltage of the 161-kV buses at Browns Ferry has not been below 160 kv.

Pa e 3 uestion 3 If 160kV is the lowest expected grid voltage, and the setpoint to trip the offsite source breakers is at or about 160kV, why annunciate below this value?

Response

The setpoint for this annunciation has been changed. Annunciation of the 161-kV bus voltage is provided when the voltage drops below 166 kV.

Pa e 3 uestion 4 Will the 480V taps be set at 5% boost?

Response

Refer to page 1, question 3 response.

Pa e 3 uestion 5 For NIMV 20, taking 160kV as lowest grid voltage, the voltage at the shutdown board is 3789V. With a voltage band on the relay of 3769 to 3845V, it appears that spurious trips of the offsite power are to be expected. As this would be in violation of GDC-17, please justify.

Response

Refer to page 1, question 2 response.

Pa e 3 uestion 6 , page 292: No diesel testing that resembles the testing called out in June 3, 1977, letter, position 3.

Response

TVA agrees to change surveillance requirement 4.9.A.l.b to read as follows: "Once per operating cycle, a test will be conducted by simulating a loss of offsite power and similar conditions that would exist with the presence of an actual safety-injection signal to demonstrate the following:

1. Deenergization of the emergency buses and load shedding from the emergency buses.

2. The diesel starts from ambient condition on the auto-start signal, energizes the emergency buses with permanently connected loads, energizes the auto-connected emergency loads through the load sequencer, and operates for greater than or equal to five minutes while its generator is loaded with the emergency loads.

3. On diesel-generator breaker trip, the loads are shed from the emergency buses and the diesel restarts on the auto-start signal, the emergency buses are energized with permanently connected loads, the auto-connected emergency loads are energized through the load sequencer, and the diesel operates for greater than or equal to five minutes while its generator is loaded with the emergency loads."

Because of the design of the Browns Ferry electrical system, it is not possible to perform this test with a simulated loss of offsite power in conjunction with a safety-injection actuation or simulated safety-injection actuation test signal. The electrical systems for units 1 and 2 are a shared system, making't difficult to perform testing on one .

unit without placing the other unit in a limiting condition for operation.

The injection signals are not designed to allow an actual signal to be initiated for one board or one loop on any of the units without affecting other boards on that unit and the other unit. More extensive temporary alterations would be required to perform this testing than is required for the present testing. This testing will be performed by simulating the applicable signals on a board-by-board basis. Verification of item 1, the deenergization of the emergency buses and load shedding from the emergency buses, will be verified in testing separate from that for items 2 and 3. The testing specified in items 2 and 3 will be included in the present emergency load acceptance test (Surveillance Instruction 4.9.A.l.b). Since the diesel generators for units 1 and 2 are shared, this testing will be performed in conjunction with the operating cycle for unit 1, utilizing the unit 1 loads only.

Pa e 3 uestion 7a r , page 294: Surveillance Requirements 4.9.A.4a, b should be monthly per NRC positions of June 3, 1977.

Response

It is TVA's position that the surveillance requirements presently specified in Surveillance Instructions 4.9.A.4.a and 4.9.A.4.b are fully adequate.

We feel that the increased frequency of surveillance specified in position 3 of the NRC letter dated June 3, 1977, could possibly produce adverse effects on the diesel generators and the associated logic circuits.

Justification for this position is given below.

1. Board transfers throughout the 4-kV and 480-V auxiliary power systems would represent unnecessary challenges to loss of power and unit trips.

2. Surveillance Instruct'ion 4.9.A.4.b requires extensive wire lifting and jumpering because of our system design. Increasing the frequency of this surveillance would increase the possibility of error and cause conflict with efforts to reduce the use of temporary alterations.

0

3. Excellent reliability of our present system has been evident by the performance of Surveillance Instruction 4.9.A.4.b. There have been no failures recorded to date, and no problems have been encountered during the performance of these surveillance tests.

Pa e 3 uestion 7b No requirement for channel check is called out.

Response

TVA will revise the existing technical specifications to provide a qualitative assessment of channel behavior during operation by observation.

Voltage readings of the 4-kV shutdown boards shall be recorded once every -12 hours.

Pa e 3 -

uestion 8A , page 297a: LOC 3. 9.B.ll does not require the failed channel to be put in tripped position within one hour or at all.

Response

The design for Browns Ferry does not lend itself to placing the failed channel in the tripped position without a temporary alteration. Since determination of a failed channel will most likely be discovered during surveillance and/or routine relay calibation testing by cognizant personnel, immediate repair or replacement will be possible. Therefore, TVA does not believe that this limiting condition for operation is required.

Pa e 3 uestion 8b LOC 3.9.B.ll.B allows all second-level relays to be inoperable for five days. ~Onl protection is loss of power relays.

Response

The limiting condition for opeation of five days is in keeping with the time frame for an inoperable shutdown board and less than the seven days allowed for an inoperable diesel generator. Therefore, TVA believes that the five-day limiting condition is reasonable and that no change is required.

Pa e 3 uestion 8c LOC 3.9.B.11.D allows all UV relays or one bus to be inoperable for five days.

Response

Refer to response for question 8b'.

0, Pa e 3 uestion 9 , page 298a, Table 4.9.A.4.c, item 3: No time delay or allowable limits defined.

Response

Refer to page 1, question 1 response.