ML18025B015

Proposed Changes to Tech Specs Re Limiting Conditions for Operation & Surveillance Requirements

ML18025B015
Person / Time
Site:	Browns Ferry
Issue date:	08/06/1980
From:	TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML18025B016	List: ML18025B015 ML19330C363
References
NUDOCS 8008080288
Download: ML18025B015 (188)

Text

ENCLOSURE 1 PROPOSED CHANGES'O TECHNICAL SPECIFICATIONS BROWNS PERRY NUCLEAR PLANT (DOCKET NOS. 50-259, 50-260)

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0 D ION F R OP RATION SURVEILLANCE RE UIREMENTS 3.9 AUXILIARY ELECTRICAL SYSTEM 4.9 AUXILIARY ELECTRICAL SYSTEM Applies to all the auxiliary elec- Applies to the periodic testing trical power systems. requirements of the auxiliary electrical systems.

Ob ective

~Ob ective To assure an adequate supply of electrical power for operation of Verify the operability of the those systems required for safety. auxiliary electrical system.

S ecification S ecifica'tion A. Auxilia Electrical E ui ment A. Auxilia Electrical E ui ment

.A reactor shall not be started l. Diesel Generators up (made critical) from the cold condition unless four units 1 a Each diesel generator and 2 diesel generators are shall be manually started:

operable, the requirements of and loaded once each month 3.9.A.4 through 3.9.A.7.are met 0 and the following off site power sources are available as. stated:

. Both 161-kV lines and common station service transformers, to demonstrate operational readiness. The test shall continue for at least a one-hour period at 75% of rated load or greatere or During the monthly gene-rator test the diesel The Unit 2 unit station service generator starting air transformer ener~ized, and compressor shall be checked for .operation and Either 161-kV trqnsmission line its ability,to recharge

. and both common itation r l service air receivers. The opera-transformers energized, or tion of the diesel fuel .

. Either. 161-kV liqe, one cool-oil transfer pumps shall be demonstrated', and the ing tower transformer, one diesel starting time to common station service trans- reach rated e'ervoltage,and former, and the bus tie board speed shall be logged.

energized and capable of power to the units 1 'upplying

b. Once per operating cycle and 2 shutdown boards. a test will be conducted to demonstrate the emer-A reactor shall not be started up gency diesel gen'erators (made critical) fr'om the Hot will start and accept Standby Condition unless all of emergency load within the following conditions are satisfied:

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FOR OPERATION SURVEILLANCE RE UIREMENTS

l. At least one of the obove sources of off site power available and capable of supplying auxiliary power to the shutdown boards.

2. Three units l and 2 diesel generators sh'all be operable.

292a

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LIMITING CONDITIONS FOR OPERATION SURVEILLANCE REQUIREMENTS 3.9.A Auxiliar Electrical E ui ment 4.9.A Auxilia Electrical E ui ment

3. An additional source .of power consist the specified time sequence.

ing of one of the followirtg:

C~ Once a month the quantity

a. A second offsite power source of diesel fuel available available 'and capable of supplyin shall be logged.

power to the shutdown boards.

'd ~ Each diesel generator shall

b. A fourth operable units be given an annual inspec-1 and 2 diesel generator. tion in accordance with instructions based on the

4. Buse's and Boards, Available. manufacturer's recommeda-tions.

a. Start buses 1A and 1B are energized. e. Once a month a sample of diesel fuel shall be checked

'or The Units 1 and 2 4kV quality. The quality shutdown boards are shall be within the accepta-energized. ble limits specified in i Table 1 of the latest revision

c. The 480-V shutdown boards to ASTM D975 and logged.

associated with the unit 0 d.

are energized.

The Units 1 6 2 Diesel Aux Boards are energized

2. D.C. Power System- Unit Batteries (250-Volt) Diesel Generator Batteries (125-Volt) and Shutdown Board Batteries (250-Volt)

e. Undervoltage relays a. Every week the specific operable on start buses gravity and the voltage of 1A and IB and 4-kV shutdown the pilot cell, and tempera-boards, A, B, C, and D. ture of an adjacent cell and overall battery voltage shall.

f. Shutdown Busses 1 & 2 energized be messured and logged.

5. The 250-Volt unit and shutdown b. Every three months the mea-board batteries and a battery surements shall be made of charger for each battery boards voltage of each cell to are operable. nearest 0.1 colt, specific gravity of each cell, and

6. Logic Systems temperature of every fifth cell. These measurements

a. Common accident signal shall be logged.

logic system is operable.

c ~ A battery rated discharge

b. 480-V. load shedding logic (capacity) test shall be system is operable. l performed and the voltage, time and output current

7. There shall be a minimqm of 103 300 measurements shall be logged gallons of diesel fuel'in the 'at intervals not to exceed standby diesel generator fuel tanks. 24 months.

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l LIMITING CONDITIONS FOR OPERATION SURVEILLANCE REQUIREMENTS 3.9.A Auxiliar Electrical E ui ment 4.9.A 'Auxilia Electrical E ui ment

3. Logic Systems

a. Both divisions of the common accident signal logic system shall be tested every 6 months to demonstrate that it will function on actuation of the core spray system of each reactor to provide an auto-matic start signal to all 4 units 1 and 2 diesel generators.

b. Once every 6 months, the condi-tion under which the 480-Volt load shedding logic system is required shall be simulated using pendant test switches and/or pushbutton test switches to de-monstrate that the load shedding logic system would initiate load shedding signals on the diesel auxiliary boards, reactor MOV boards, and the 480-Volt shut-down boards.

4. Undervoltage Relays a~ Once every 6 months, the con-under which the under- 'ition voltage relays are required shall be simulated with an undervoltage on start buses 1A and 1B to demonstrate. that the diesel generators will start.

b. Once every 6 months, the con-ditions under which the under-voltage relays are required shall be, simulated with an

'undervoltage on each shutdown board to demonstrate that the associated diesel generator will start.

C~ The undervoltage relays, which start the diesel generators from start buses lA and 1B and the 4-kV shutdown boards, shall be calibrated annually for trip and reset and the measurements logged.,'These relays 294 shall be calibrated as specified in Table 4.9.A.4.c'

LIHLiZH R UIREMENTS 3.9.3 0 eration with Ino erable 4.9eB 0 eration with Ino erable

~Eut ment ~tut ment Whenever a reactor is in Startup mode or Run mode and not in a cold condition, the availability of electric power shall be as speci-fied in 3.9.A, except as specified herein.

1. From and after the date that When one of the two required off site one of the two required off power sources is found to be site power sources or, one .inoperable, all units 1 and 2 diesel start bus becomes inoperable generators and associated boards reactor operation is must be demonstrated to be operable permissible for seven days immediately and daily thereafter.

2. From and after the date that 2~ When the 4-kV bus tie board is the 4kV bus tie board becomes inoperable and only two off site inoperable reactor operation power sources are available, they is permissable for 30 days .shall be shown to be energized if two off site power sources daily.

are available. If three off site sources exist ~ operatio 3~ When one of the units 1 and 2 diesel is permitted indefinitely. generator is found to be inoperable, all of the CS, RHR (LPCI and Contain-

3. When one of the units 1 and 2 ment Cooling) Systems and the diesel generators is inopera51e remaining diesel generators and continued reactor operation i diesel generators and associated permissible during the suc- boards shall be demonstrated to be ceeding 7 days, provided that I operable immediately and daily two offsite power sources are thereafter.

available, and all of the CS, RHR (LPCI and Containment Cooling) Systems, and the remaining three units 1 and 2 diesel'generators are operable.

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• LIMITING CONDITIONS FOR OPERATION SURVEILLANCE RE UIREMENTS 3.9.B 0 eration with Ino erational 4'9.B eration with Ino erable

~Euk ment EcCEuk ment When one units 1 and 2 4-kV 4. When one 4-kV shutdown boarc's shutdown board is inoperable, found to be inoperable, all continued reactor operation remaining 4-kV shutdown boards is permissible for a period and associated diesel genera-not to exceed 5 days, provided tors, CS and RHR (LPCI and that two off-site power sources Containment Cooling) Systems are available and the remain- supplied by the remaining 4-kV ing 4-kV shutdown boards and shutdown boards .shall be demon-associated diesel generators, strated to be operable, imme-CS, RHR (LPCI and Containment diately and daily thereafter.

Cooling) Systems, and all 480 V emergency power boards are 5. When one shutdown bus is found operable. to be inoperable all 1 &' diesel generators shall be proven operable

5. When one of the shutdown busses immediately and daily thereafter.

is inoperable reactor operation is permissible for a period 6. Wh'en one units 1 & 2 diesel of 7 days. Aux board is found to be inoperable the remaining diesel

6. When one of the 480V diesel Aux board and each unit 1 & 2 Aux. boards becomes inoperable diesel generator shall be proven reactor operation is permissibl operable immediately and daily .

for a period of 5 days. thereafter.

7. From and after the date that on of the three 250-Volt unit bat-teries and/or its associated battery board is found to be inoperable fox any reason, continued reactor'peration is permissible during the succeed-ing seven days. except for routine surveillapce testing the NRC shall be notified within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of the situation, the precautions to be taken during this period and the plans to re-turn the failed component to an operable state.

From and after the date that one of the four 250-Volt shutdown 296

LIMITING CONDITIONS FOR OPERATION SURVEILLANCE REQUIREMENTS 3.9.B 0 eration with Ino erational 4.9.B 0 eration. with Ino erable

~Euf ment ~Eu1 ment board batteries and/or its associated battery board is found to be inoperable for any reason, continued reac-tor operation is permissible during the succeeding five days in accordance with 3.9.B;4.

9. When one division of the Logic System is inoperable', continued reactor operation is permissible under this condition for seven days, provided the CSCS require-ments listed in specification 3.9.B.2 are satisfied. The NRC shall be notified within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of the"situation, the precautions to be taken during this period and the plans to return the failed component to an operable state.

10. Undervoltage relays on 1A,or 1B start bus may be inoperable for a period of 7 days provided the'ther start bus 'and under-voltage relay are operable (within surveillance schedule of 4.9.A.4.a).

11. The following limiting conditions for operation exist for the undervoltage relays which start the diesel generators on t'e 4-kV shutdown boards.

A. Undervoltage relays which start the diesel generators for a complete loss of volt-age on a 4-kV shutdown board may be inoperable for 5 days provided the degraded voltage sensing relays on that shutdo board are fully operable (within the surveillance schedule of 4.9.'A.4.b) .

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SURVEILLANCE REQUIREMENTS 3.9.B eration with Ino erable EccEui mene B. Undervoltage relays~hich start the diesel generators for degraded voltage on a 4-kV shutdown board may be inoper-able for 5 days provided the complete loss of voltage relays on that shutdown board are operable (within the surveillance schedule of 4.9,A.4.b).

C. One of the three phase-to-phase undervoltage relays provided to detect a degraded voltage condition on a 4-kV shutdown board may be inoper-able for 15 days provided both of the following con-ditions are satisfied.

1. The other two phase-to-phase undervoltage relays provided to detect degraded voltage on that 4-kV shutdown board are operable (within the surveil-lance schedule of 4.9.A.4.b). "

2. The complete loss of voltage relays on that shutdown board are operable (within the surveillance schedule of 4.9.A.4.b).

D. Both complete sets of under-voltage relays (degraded voltage and complete loss of voltage) may:be inoperable for 5 days provided the other shutdown boards and undervoltage relays are operable (within the surveillance schedule of 4.9.A.4.}7) ~

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U REMENTS 3.9.B 0 eration with Ino erable

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12. When one 480-volt shutdown board is found to be inoperable, the reactor will be placed in hot standby withi 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and will be in cold shutdown within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

13. If the requirements for operating in the conditions specified by 3.9.B.l through 3.9.B'.12 cannot be met, an orderly shutdown shall be initiated and the reactor shall be shutdown and in thy cold condition within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

0 297b

LIMITING CONDITIONS FOR OPERATION SURVEILLANCE REQUIREMENTS 3.9.C 0 eration in. Cold Shutdown Whenever both reactors are in cold shutdown condition with, irradiated fuel in either reactor, the avail-ability of electric power shall be as specified in section 3.9.A except as specified"herein.

l. At least two units 1 and 2 diesel generators and their associated 4-kV shutdown board shall be operable. t

2. An additional source of power consisting of at least one of the following:

a. The Unit 1 or 2 unit stati service transformer energized.

0 b. One line 161-kV transmission common and its associated station service transformer energized.

C~ Either 161-kV line, one tower transformer 'ooling and the bus tie board energized and capable of supplying. power to the units 1 and 2 shutdown boards energized.

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'd ~ A third ope'rable diesel generator.

3. At least one 480-V shutdown board for each unit must be operable.,

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0 Table 4.9.A.4.c VOLTAGE RELAY SETPOENTS/DEESEL GENERATOR START Rela Location Tri Level Settin Remarks

l. 4-kV Start Bus 1A and 1B Trip Setpoint: 0 volts with a 5-second Start diesel generators time delay. on loss of offsite power.

Allowable Values:- +.1 second Trip Range: 4.9 to 5.1 seconds Reset Setpoint: 2870-V Allowable Values: -

+2/ of 2870 Reset Range: 2813-V to 2927-V J

2. 4-kV shutdown Boards Trip Setpoint: 0 volts with a 1.5-second Start diesel generators time delay. on loss of offsite power.

Allowable Values: +.1 second Trip Range: 1.4 to 1.6 seconds Reset Setpoint: 2870-V Allowable Values: +2% of 2870-V Reset Range: 2813-V to 2927-V

3. 4-kV Shutdown Boards Trip Setpoint: 3807-V Second level undervoltage delays start diesel

'ensing Allowable Values: +1% of 3807-V generators on degraded voltage.

Trip Range: 3769-U to 3845-V Reset Setpoint: 3883-V Allowable Values: +1% of .3883-V Reset Range: 3844-V to 3922-V

The obgective of this specification is to assure an adequate source of electrical power to operate facilities to cool the plant during shut-down and to operate the engineered safeguaxds following an accident.

There are three sources of alternating curxent electrical energy available, namely, the 161-kV transmission system, the nuclear genera-ting unit transformer and the diesel generators.

The generator breaker for unit 2 can provide a non-interruptible source of off site power from the 500-kU transmission system to the units 1 and 2 shutdown boards. A source of auxiliary power can be supplied from the 161-kV transmission system through the common station service transformers or the cooling tower transformer by way of the bus tie board. The 4kV bus tie board may remain out qf service for 30 days as long as two off site power sources are available, If three off site power sources are available the bus tie board may,remain out of service indefinitely.

The minimum fuel oil requirement of 103,300 gallons is sufficient for 7 days of full load operation of 3 diesels and is conservatively based on availability of a replenishment supply.

A 4-kV shutdown board is allowed to be out of operation for a brief period to allow for for maintenance and testing, providing all remaining 4-kV shutdown boards and associated diesel generators CS, RHR (LPCI and Containment Cooling) Systems supplied by the remaining 4-kV shutdown boards, and all emergency 480V power boards are operable. The degraded voltage sensing relays provide a start signal to the diesel generators in the event that a deteriorated voltage condition exists on a 4-kV shutdown board. This starting signal is independent of the starting signal generated by the complete loss of voltage relays and will continue to function and start the diesel generators, on complete loss of voltage should the loss of voltage relays become inoperable. The 15-day inoperable time limit specified when one of the three phase-to-phase degraded voltage relays is inoperable is

)ustified based on the two out of three permissive logic scheme provided with these relays.

There are eight 250-volt d-c battery systems each of which consists of a battery, battery chaxger, and distribution equipment. Three of these sys-tems provide power fear unit control functions, operative power fox unit motor loads, and alternative drive power for a 115-volt a-c unit preferred motor-generator set. One 250-volt d-c system provides power for common plant and transmission system control functions, drive power fox a 115-volt a-c plant preferred motor-generator set, and emergency drive power for certain unit large motor loads. The four remaining systems deliver con-trol power to the 4160-volt shutdown boards.

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ENCLOSURE 2 DESCRIPTION OF PROPOSED PER5ANENT ARRANGENENT OF UNDERVOLTAGE CORRECTIVE MODIFICATIONS FOR BROWNS PERRY NUCLEAR PLANT

TABLE OF COHTEHTS 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 SYSTE5 8.2. 1 Descri ption of Utility Grid and Preferred Power 8 2-1 8.2.2 Analysis 8.2-.2 8.3 ~OR~AL AUXILIARY POWER SYSTEH  !

8 3 1 General 8 3-1 832 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 8~ 3 5 Description 8 3-3 8 3.6 Safety Evaluation 8 3-7 8.3 7 Inspectioq. anl Testing 8 3-10 1

0 LXST OF TABLES Title Auxiliary Poorer Supplies and Bus Transfer Schemes

LIST OF FIGURES Fi ure No. Title 811-1 TVA Transmission System 8 2.2-1 Typical Normal Conditions Loads on USST's 8 22-2 Trip Three Units - Loads on USSTis

8. 2 2-3 LOCA Unit 1, Trip Units 2 6 3 Loads on USST Is 8 22-0 Trip Three Units - Loads of Units' 8 3 on USSTis, Loads of Unit 1 on CSST's 8 2.2-5 Trip Three Units - Loads of Units 1 S 2 on USSTIs, Loads of Unit 3 on CSST's 8 2.2-6 Browns Ferry 20.7-kV Unit 1 Bus Voltage 6 Frequency Loss of One Cumberland Unit - Loads on USST I s 822-7 Browns Ferry 20.7-kV Unit 1 Bus Voltage 8 Frequency -- Loss of One Browns Ferry Unit Loads on USST's

8. 2.2-8 Browns Ferry 20.7-kV Unit 1 Bus Voltage 6 Frequency Loss of Three Browns Ferry Units Loads on USSTis 8 2 2-9 Browns Ferry 20.7-kV Unit 1'us, Voltage 8 Frequency Three Phase Fault on Unit 3 Terminals Loads on USST's 8 2 2-10 Browns Ferry 161-kV Bus Voltage 8 Frequency - Loss of a Cumberland Unit. - Loads on DSST's 8.2 2-11 Browns Ferry 161-kV Bus Voltage 6 Frequency - Loss of One Browns Frerry Unit Hith Its Station Service Load Transferred to CSST's 8 2 2-12 Browns Perry 161-kV Bus Voltage 8 Frequency - Loss of Three Browns Ferry Units, Loads of Unit 3 on CSSTIs, Units 1 8 2 Loads on USSTIs 8-2 2-13 Browns Ferry 161-kV Bus Voltage 8 Frequency Three Phase Faul,t

LIST OF FIGURES (cont.)

Fi ure No Title on Unit 3 Terminals, Loads of Unit 3 on CSSTIs, Units 1 6 2 Loads on USST's 8 3-1a Key Diagram of Hormal Auxiliary Power System Units 1 and 2 8 3 ~ 1b Key Diagram of Standby Auxiliary Power System Units 1 and 2 I 8 3-2 Key Diagram of Hormal and Standby Auxiliary Power System - Unit 3

BFNP 8 1 INTR0DUcTI0N 8.1 1 Utilit Grid and Interconnections The Tennessee Valley Authority. (TVA) is a corporate agency of the United States Government serving the. State of Tennessee and parts of six other states in the southeast on the boundaries of Tennessee. TVA is interconnected with electric power companies to the north, west, south, and east of its service area. As 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 thxough 500 kV The Browns Ferry 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'f the nuclear unit's is connected into TVA's 500-kV transmission system. The six 500-kV transmission connections consist of two lines to the ladison 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 connected into the 161-kV transmission system through one line to the Trinity 500-161-kV Substation and one line to the Athens, Alabama, 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 wit) sources of offsite electrical power to meet the requirements of GDC-17 t

8.1.2 Plant Electrical Power S stem Under normal operating conditions each nuclear power unit is supplied electric power 'from its main generator via the unit stapion service transformers. During normal startup and shutdown the unitIs main generator is isolated by a generator breaker, and electric power is supplied to the unit auxiliary power system from the 500-kV offsite grid via the main transformers.. Xf electxic power from the 500-kV grid is unavailable to a particular unit, power is then supplied from two 161-kV transmission lines via two common station service transformers.

In addition, two cooling tower transfoxmers provide a backup souxce of power for units 1~ 2, and 3 shutdown loads.

The standby source of auxiliary power is from eight diesel-driven generators. These units start automatically on loss of voltage

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BEBOP or a degraded voltage on the associated shutdown board from self-contained starting air systems.

250-Volt d-c Batter stems There are nine 250-volt d-c battery systems each of which consists of a battery, battery charger, and distribution equipment. (One additional 250-V d-c plant battery system will be available in approximately two years). Three of these systems provide power for unit control functions, opexative 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 pxovides power for common plant and transmission system ccntrol functions, drive power for a 115-volt a-c plant preferxe'd motor-genexator set, and emergency drive power for certain large motor loads, (e.g., lube oil pump). The five remaining systems deliver control power to .the 4'l60-volt shutdown boards.

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

Taro of these systems provide power to the two annunciator systems and the third is the power source for the plant telephone system.

1 15-Volt a-c Unit Preferred S stems The three 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 contjnous 115-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 H I

There are two 115-volt a-.c instrument and control power buses fox each of the three generating units Each of the instrument and control power buses is supplied by its associated 480- to 115-V transformers which in turn are each supplied from independent 480-V shutdown buses. This provides an independent 115-volt a-c control power bus for each of the redundant control and instrumentation channels for each unit.

115-volt a-c Plant Preferred 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 char+ drives, clocks, and certain communication equipment~

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BFNP 8~2 OPFSITE POWER SYSTEM 8.2 1 Descri tion of Otilit Grid and Preferred 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 adde'd in 1981. The 161-kV switchyard is supplied by two 161-kV transmission lines. These sources have the capacity and capability to meet the requirements of GDC-17.

The 500-kU connections consist of two lines 37.42 and 40.26 miles long to the Madison 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 in service by 1981) I 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-kU Substation, 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-kU Transmission Line, crosses under all of the 500-kV transmission lines emanating from the BroWs 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 500-kV or the 161-kV transmission systems. A tower failure in the riper crossing could remove from service two 500-kV and one 161-kV circuits while a tower failure -in any other area 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 parallel 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. new Browns Ferry-Cordova 500-kV Transmission Line near the Browns Ferry Nuclear Plant. The lines in this section are separated sufficiently to ensure ghat the failure of any tower in one line 0 could remove from service no more than one 500-kV and one 161-kV circuit.

8. 2-1

BFNP 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 hare conductors and vertical loading strength based on approximately 1-1/4-inch radial ice. These loading conditions assure strength to provide adequate reliability under weather conditions encountered on TVA~s transmission line 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. TVAIs 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), during only one incident in the adjacent service area.

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

Transmission lines in the'00-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 is 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 Perry-Athens 161-kV Transmission Line is 10 operations in the last six years because of lightning.

The use of circuit breakers with automatic xeclosing results in most of these 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. 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 sis The seven transmission lines (six existing and one future)

'connected to the 500-.kV'switchyard and the two transmission lines conne'cted to the,161-kV'witchyard have sufficient capacity to supply the total required power to the plant's electrical, auxiliary power system under normal, shutdown, and loss of coolant accident (LOCA): conditions for any single transmission contingency. Power reaches the plant from the 500-kV system through the main transformers and the unit station service transformers, and from the 161-kV system ovex'wo physically independent 161-kV transmission lines through the common station service transformers an( the cooling tower transformers. These 0 souxces have sufficient capacity to supply all loads. Separation ofthe lines, the p, retention systems, and a strong transmission' 2-2

0 BFNP grid minimize the probability of simultaneous failures of offsite power sources. Steady-state studies show these offsite sources to be capable of supplying the onsite power system when all nuclear units are simultaneously removed from service Transient stability studies included conditions of three-phase faul'ts on generator terminals in which one unit was disconnected automatically from the transmission system as a result of these disturbances. Other transient stability studies included loss of TVA's largest unit, loss of one Browns Ferry unit, and the simultaneous loss of three Browns Ferry units. These transient stability cases were considered to be the most serious conditions of postulated transmission disturbances. They show that the transmission system remains stable with negligible disturbance to the offsite power sources. t Steady-state studies 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. In 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 normal conditions, (2) trip three units with all loads on unit station service transformers,'3) LOCA of unit one and 'trip of units 2 and 3 with aU. loads on unit. station service transformers, (4) trip of three units with load of unit 1 on the common station service transformers~ and loads of units 2 arid 3 on unit station service'transformers, and (5) trip of three Browns Ferry units with load of unit 3 on the common station service transformers an loads of units 1 and 2'n unit station service transformers..

Figures 8.2.2-6 through 8 2 2-9 show voltage and frequency at Browns Ferry unit 1 unit station service bus 20.7-kV nominal for (6) loss of a 1300-5W generator at TVA's. Cumberland Steam Plant, which is one of TUA's two largest generating units, {7) loss of one Browns Ferry unit, (8) loss of three Browns Perry units, (9) three-phase fault on unit 3 generator terminal with loads remaining on unit station service transformers. Figures 8.2.2-10 through 8.2.2-13 show voltage and frequency at the Browns Perry 161-kV bus for (10) loss of a 1300-5W generator at TVA~s Cumberland Steam Plant,'hich is one of TVA's .two largest 0 generating units, {11) loss of one Browns Ferry unit with its load transferred to common station service transformers, (12)

II 8 2-3

BFNP loss of three Browns Perry units with loads of unit 3 on the common station service transformers and the Loads of unit 1 and unit 2 on the unit station service transformers, and (13) a three-phase fault on unit 3 generator terminal with its loads transferred to the common station'ervice transformer at 36 cycles Browns Ferry unit 2 has .identical parameters as unit 1 and, as such, all studies relative to unit 1 would he applicable to unit 2 provided identical conditions are applied to unit 2.

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BFHP 8.3 Normal Auxilia Power S stem 8.3. 1 General The plant electric power system consists of the main generators, the main step-up transformers, the unit station service transformers, the common station service transformers, the diesel generator units, the batteries, and the electric distribution system as shown on Figures 8.3-1a 8 b, 8.3-2 and 8.3-3. 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 1oad side generator breaker termirjals and the low-voltage connection of the maih transformers. The 'generator breaker has an interrupting capacity of 165,000 amperes at rated maximum voltage, a continuous current rating of 36 F 000 amperes with a 4.8 cycle interrupting time, and a rated voltage of 24KV(RHS).

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 1 and 2, 4 for unit 3) .

Zn 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 t

preferred offsite circu$ to the 500-kV switchyard for any unit brings about an automatic transfer for both safety- and buses toIthe-common station service transformers.

non-.'afety-related Xf this supply subsequently fails, only the safety-related buses (class 1E system) are aptomatically transferred to the standby (onsite) electric power<sources.

8.3.2 Power Generation ob ective The basic function of tpe normal auxiliary electrical power system is to provide poyer 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 normal auxiliary power system is to furnish power to startup and operate all the station, auxiliary loads necessary for plant operation, and to furniph normal and alternate sources of power 0 for safe shutdown. The emergency sources of power for safe l 8 3-1

BFHP shutdown will be provided by the diesel generators 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 operat'ion in a safe and efficient manner.

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

3. These sources ant 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.

The system shall have a high degree of reliability.

8.3. 4 Safet Desi n Basis

1. The normal auxiliary power system shall be designed to provide sufficient normal 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 capacity of these sources when degraded to a fraction of their normal capacity shall be sufficient to supply the power required to shutd~ the plant and maintain it in a safe condition under normal or accident situations.

4. The buses shall be arranged so that essential loads can be easily transferred Po 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.

P Reference is made to Figures 8.3-1a and 8.3-2, Key Diagrams of Hormal Auxiliary Power System, which shows the arrangement, source connections, and source xatings 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 8 3-2

BFNP provided to expLain the flow of power, transfers betw'een normal and alternate sources, and pertinent operational comments on each of the hoards and buses involved in the normal and standby auxiliary power systems.

8.3 5.1 Unit Common Station Service and Coolin Tower Transformers 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 transfoxmer secondary t

The transformers are three-phase, double-secondary, outdoor type, oil filled, class OA/FA and OA/FA/FOA, rated for 550C temperature rise but with 654C rise insulation. The transformers manufactured, and tested in accordance with TVA are'esigned, standard specification 54.080 Transformer secondaries axe wye-connected with xesistance-, 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. Each is capable of operating continuously with no loss of life at 112% of rating at 65oC temperature rise.

Unj.t station service transformers 1B~ 2B, and 3B, which provide the normal supply of poyer fox operational loads on 4160V A and B unit hoards and the safety-related buses from the main generator or 500-kV grid, are equipped with automatic load tap changers on the primary winding that can xegulate the voltage over a +-1'0-,

percent xange. The autpmatic load tap changers operate from signals received from vpltage sensors on the 4160V transformer secondary which monitorp the voltage levels. Upon 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) and after a time delay set for 2.0 seconds, the voltage sensors transmit a signal to the load tap changers to compens'ate for the voltage change.

The automatic load tap changers on the unit station service transformers have a voltage range from 18630 volts to 22770 volts with the equivalent of 17 possible tranformation ratios. The time required to change a tap position after receiving a signal from the voltage sensors is 2 0 seconds Remote manual control of the load tap changers also from the Hain 0 can be accomplished Ccntrol Room.

8 ~ 3-3

o BFHP

~ Both common station service transformers in service are capable of continuously carrying the load consisting of. the station common auxiliaries~ plus all auxiliaries of one generating unit operating at full load without, one unit station service transformer, plus all auxiliaries of another unit either'n the starting mode, the shutdown mode, or the accident mode.

The unit station service transformers are capable of continuously carrying the load consisting of all auxiliaries of one generating unit operating at full load plus either (1) the load on one of the two common auxilairy buses or {2) the maximum load on. one of the two shutdown buses with another generating unit in the accident mode.

8.3,. 5 2 4160-Volt stems The 4160-volt unit boar) 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 the air-magnet'ic type. Power connections from the station service transformer to the switchgear are with nonsegregated buses'.

The unit and common station service transformers, cooling tower transformers, and 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 sec)ion and the startup buses have breakers interlopked to prevent paralleling power sources, their'ource 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 normal supply, or by acbidental 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 sourcet the short circuit current, and the breaker short circuit current capabilities are taken into account.

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

8o 3-4

o' BFNP Each circuit breakex is provided with 2SO-volt d-c stored-energy mechanism; mechanism-operated, ceD-mounted auxiliary switch with sufficient contacts for all required interlocking; cuxrent transformers for metering and relaying; and necessaxy switchgeax-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 4160-080-V transformer primary breaker is provided with two current transformers (one in phase k and one in phase C) for metering and phase o'vercurrent relaying and one ground sensor current transformer for ground relaying. Each 'includes induction-type overcurrent relays and an instantaneous ground ovexcurrent 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 secondaxy 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 wattmetex, and one voltmeter with a transfer switch. One ammeter and transfer switch is provided on each motor and 0160-080-V transformer feeder. One voltmeter and transfer switch is provided on each switchboard bus section.

Eetal-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 thy start buses to switchgear. Bus ducCs axe furnished with a continuous current rating as required for the full transformer or'oad rating.

Each switchgear bus and startup bus section is provided with a three-phase set of differential relays of the high-speed induction overcurxent 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 transformer has differential ovexcurrent protection. Each secondary breaker is provided with three current transformers for differential relaying only.

Each main and bus tie breaker is provided with three current in addition to those for differential relaying, for

'ransformers

8. 3-5

i BFHP use with metering and overcurxent 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 Zoad Center Unit Substations Each substation consists of 4160-480-V transformers, primary terminal box, and close-coupled or bus duct connected 480-Vg metal-enclosed switchgear.

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 s+stations have electxically operated main breakers and with the eqception of the 480-V shutdown board, automatic bus txansfer schemes.

Askarel-insulated transformers are connected to the switchgeax so that the transformer can be enclosed with a curb to contain the Askarel in case of a tank rupture.

Transformers are liquid filled, askarel insulated, three-phase, delta-delta, 60-kV BIL, rated for 554C temperature rise but with 654C rise insulation for 12% margin in continuous capability.

Transformers are class OA/fut PA except where dual ratings are shown in Figuxes 8.3-1a, 8.3-1b, and 8.3-2, in which cases transformers are class OA/FA. A no-load tap changer handle,'ith means for padlocking, is provided outside the tank.

<tain and bus tie breakers and the main switchgear bus axe rated 1600 or 600 amperes, depending on the maximum transformer capability, and in accor'dance with USA Standard C37.16.

Each circuit breaker hay three poles, and is electrically and mechanically trip free pith eithex long time and instantaneous or long time and short time overcurrent trip devices unless overcuxrent relays axe provided. The circuit breakers have manual or electrical stpred-energy closing mechanism, mechanical pushbotton 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 overcurrent tripping.

Breakers serving motor control centers or panelboards are

'anually operated with short time selective and long time series overcurrent tripping.

480-v lighting switchge'ar have main breakers with short time 0 selective and long time series overcurrent tripping, and have key interlocking between m~in breakers 8 3-6

All other 480-V switchhear 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 overvoltage relay and auxiliary relay for initiating automatic bus transfer and automati.cally 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.

8.3. 5.4 480-V Hotor Control Centers Hotor control centers are in accordance with HEHA Standard IC1.

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

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

Each single-speed motor starter has two hand reset overload relays. Each two-speed motor starter has two overload relays for each speed.

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 normal auxiliary power system are those which are widely appliep for utility and industrial applications.

In such applications, the usage frequently demands reliability ccmparable to that of the requirements under consideration herein. Bore 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 HPA~ HGA, and HEA auxiliary relays for necessary multiplication of contacts to achieve simultaneous functions, General Electric type CR2820'

.3-7

BFHP motor-driven timing relays and General Electric type SB-1 or SB5 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 instance, should one of the-4. 16-kV buses fail to be energized 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.

h 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 power supply are sufficient in number and capacity, and of such electrical and physical 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.

rn the event of a total loss of all normal auxiliary power system sources, auxiliary power is supplied from standby diesel generators located on the site (safety-related boards only).

The multiplicity of Linjs 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 'lLlso, the design utilizes physical separation of buses and service components to limit or localize the consequences of electrical faults or mechanicaL accidents ocqurring at any point in the system.

The plant is designed to shut down safely on complete loss of offsite electrical 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 po~er normally comes from outside sources as described above. k high degree of reliability in the auxiliary power system contributes to continuity of operation and hence to safety.

8 3-8

BFNP 0 If unit generators are incapacitated the generator breaker will be opened and auxiliary power backfed from the 5QO-kV system.

There are still two other independent sources of auxiliary power; the 161-kV system and the diesel generators. 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 4-kV unit boards, however, they can be manually transferred to the cooling tower transformers via the 0-kV bus tie board. Unit 3 shutdown boards receive normal power via the 4-kV unit boards 3A and 3B with an automatic backup connection to the cooling tower transformer source'hrough the 4-kV bus tie board. Table 8.3-1 is a listing of the normal auxiliary power supplies and bus trans fer schemes At no time will loss of auxiliary power prevent .scram since stored pneumatic energy and normal reactor pressure or stored pneumatic energy alone at 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 ccntrol board is located between units 1 and 2 control boards.

The control functions of the normal auxiliary power system which are unit-related only, such as feeder and load breaker operation, are located on the respective unit control boards only. The electrical control functions which are shared by all three units, such as feeder breaker 9peration to the common 4160-V board, are located on the electrical control board I

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 injection pump, and reactor core isolation cooling system pump (these are steam turbine-driven) are powered by electric drives. Under 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 all three units are supplied from the common station service transformers.

8 3-9

C BFHP Recirculation pump boards 1, 2 and 3 supply only the variable

~

frequency generator sets of the recirculation pump motors The high voltage drop incurxed 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, 2C, 3A, 3B, and 3C 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 hoards. 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 hoards are located within seismic Class I Buildings. 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 unit station service transformers, the common station service system, and cooling tower transformers will be used before use the standby diesel generators.

it becomes necessary to If all sources of power other than the diesel generators are lost, provision is made 'afor manual connecting the diesel enerators to back feed.

gene 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 generators with the normal auxiliary power sources should they return 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.

Koads and systems which are common to all three units, except, standby emergency systems, are supplied from common boaxds A and B which are normally fed by the common station service transformers.

8.3.7 Ins ection and Testin I

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 ipclude expanded operational tests of functions related to reactor safety. The discussion here is limited to quality assurance and field setting of components in the auxilixy power system.

0 8 3-10

BPNP All transformers, switchgear, and motor control centers are subjected, as a minimum, to factory tests required under HE51L and ASSI standards. These tests include dielectric tests, electrical and mechanical operation of circuit breakers and contractors, and measurement of transformer-constants. Hanufacturer~s certified test reports are submitted to TVA for review and approval.

TVA maintains a force of inspectors who review the manufactureris work during pxoduction, and who permit release of equipment for shipment from the factory only after assuring themselves that the equipment is complete, has been manufactured in accordance with the specifications, that specified tests have been pexformed, and that the equipment is of high quality. The equipment is again inspected for damage in shipment befoxe acceptance at the jobsite.

8.3 7.3 Field Tests all tests xequired to determine t

TVA construction forces perform that the auxiliary power equipment will function safely, reliably, and as designed. These tests are made prior to energizing the equipment. Examples of these tests are: detailed check of small wiring, meggering of all electrical power 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" 3-11

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

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

2. .Each bus has provision for manually transferring between normal and alternate sources.

nanual transfers of all 0160-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.

u. The term "high-speed transfer" applies to u160-V bus transfers between stored-energy circuit breakers which are controlled for a dead time not exceeding 5 cycles.

5. The term "delayed transfer< applies to 0160-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 connected motors. Bormally the residual voltage relay will be set at 30% 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 080-V buses normally supplied from main 080-V buses of the normal auxiliary power system, all 080-V automatic bus transfers are blocked by bus overcurrent protective devices.

Auxiliary Power Supplies Table B- -'I and Bus Transfer Schemes Sheet 2 0

Power Sources Item Board and/or 5ain Bus Normal alternate Remarks 1, 41bO-V Bus lh Start bd 1 Start C05 SS TR hr X-winding fed frcm C05 SS TR Br X-winding fed from Automatic high speed transfer from the normal to the alternate Athens or Trinity Athens or Trinity source is initiated by operation 161 kV lines 161 kV lines of protective relays for the normal source common station service trans-former, or for the 161-kV line feeding that transformer. Automatic delayed transfer from the normal to the alternate source is initiated by time delay undervoltage relays.

The bus will be automatically returned to its normal source 40 cycles after return of voltage on the normal source. Tpis time delay is to avoid needless switching during 161-kV line reclosing opera-tions. If alternate source

'is abnormally lov, the normalvoltage source breaker will not trip (no transfer); if the normal source breaker trips again within 15 seconds, it will lock out vith an alarm, and operator reset vill be required. Loss of voltage for a time in excess of 1.5 seconds results in a signal for automatic starting of all diesel generators.

4160-V Start M 1 - Start C05 SS TR Br C05 SS TR hr Bus 1B X-+ndingr fed from X~inding fed from Athens or Trinity Athens or Trinity 161 kV lines 161 kw lines 4160-V Start M 2 - Start C05 SS TR hr C05 SS TR Br Bus 2A Y-winding fed from Y~inding fed from athens or Trinity Athens or Trinity 161 kV lines 161 kV lines 4160-V Start M 2 - Start C05 SS TR Br C05 SS TR hr Bus 25 Y-winding fed from Y-winding fed from Athens or Trinity Athens or Trinity

'l61 kV lines 161 kV lines 4160-V Bus Tie Roard Cooling Tower Transf Cooling Tower Transf Banual transfer from the normal TCT1 TCT2 power source to the alternate power source, or visa versa is provided by operating breakers 1920 and 1930 by means of control switches for these breakers provided on the 4160-V cooling tower switchgear A.

Auxiliary power Supplies Table and Bus Transfer Schemes - Sheet 3 0

Power Sources Item Board and/or Bain Bus Normal Alternate Remarks Alternate 1 5 Shutdown Bus 1 (4160-V) 4 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 preselected tor assigned 4160-V shutdown boards, "normal" ) with each bus serving as the normal source to two boards and as the

'lternate 2 alternate source to the two other boards 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-selected manually start bus 1A or 1B as the normal source 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 source. Automatic if required for back-feeding a pre-selected high"speed transfer from the nor-mal to an alternate 1 source 4 kV unit bd (1A, 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 source is not available, the transfer is prevented, and the Alternate normal source becomes alternate 2 Bus tie Board 4

source. Automatic transfer blocked after time delay in the ii presence of an accident signal.

Alternate 3 and 4 sources may be selected manually'nly.

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

Alternate 2 Same 4 kV unit M of pre-selected unit, but fed from start bus 1A or 18

. Alternate 3 Two diesel generators, if required for back-feeding a pre-selected 4 kV

Auxiliary Power Supplies Table 8.3-1 and Bus Transfer Schemes - Sheet 4 0

Power Sources Item Board and/or Bain Bus Normal A lte mate Remark unit bd, (1B, 2A) See also remarks for items 13, 14, 15, and 16 Alternate 4 Bus tie board 4 kV Recirculation Pump Boards:

(a) Unit 1, Pump 5-G Set 1A Unit SS TR 1h Start Bus 2A Automatic high-speed transfer Y-winding from the normal to the alternate source is i.nitiated by main generator unit trip relays.

BD1 for both Automatic delayed transfer from the normal to the alternate source is initiated by high-speed voltage.

relay-(b) Unit lg Pump 5-G Set 1B Start Bus 2B (c) Unit 2, Pump B-G Set 2A Unit SS TR 2A Start Bus 2A Y-wind ing BD2 for both (d) Unit 2, Pump 5-G Set 2B Start Bus 2B (e) Unit 3, Pump 5-G Set 3A Unit SS TR 3h Start Bus 2A Y-winding (f) 'nit 3, Pump 5-G Set 3B BD3 for both Start Bus 2B 4 kV Unit Boards, Unit 1 Alternate 1 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 main generator unit trip relays or by an accident signal. lutomatic delayed transfer from the normal to the alternate 1 source is initiated by a time delay vol-tage relay.

alternate 2 Backfeed from shut-down bus Alternate 1

Table 8 -1 auxiliary Power Supplies and Bus Transfer Schemes Sheet 5 Power Sources Board and/or Hain Bus Nonral Alternate Remarks (b$ kV unit bd 18 Unit SS TR 1B Start hus 1B Y-winding Alternate 2 Backfeed from shut-down bus Alternate 1 (c) 0 kV unit bd 1C Unit SS TR 1h Start hus 1B X-windin~

9 0 kV Unit Boards, Unit 2 Secondary 1 of:

Alternate 1 (a) 0 kV unit hd 2i Unit SS TR 2B Start, Bus 1i X-winding llternate 2 Backfeed from shut-down buses Alternate 1 (b) 4 kV unit bd 2B Unit SS TR 2B Start Bus 1B Y-winding Alternate 2 Backfeed from shut-down buses Alternate 1 (c) 0 kV unit bd 2C Unit SS TR 2i Start bus 1i X-'winding

.10 .. 4 kV Unit Boards ~ Unit 3 1

'econdary "of:

Alternate 1 (a) 0 kV unit bd 3A Unit SS TR 3B Start hus 1h To permit use of the condensers X-wind ing as heat sinks for the possible caie of normal power outage at the.

plant, the plant design includes a mode of operation for one running condenser circulating water pump.

0 Table 8.. -1 auxiliary Power Supplies and Bus Transfer schemes - Sheet 6 Power Sources Item Board and/or Bain Bus NOtlnal Alternate Remarks Alternate 2 Backfeed from shut-down boards Alternate 1 (b) 4 kV unit 38 Unit SS TR 38 Start bus 18 The controls provide for. back-Y-vind ing feeding from the shutdown boards

• , to the 4160-V unit boards A and 8 on each unit, with the boards loaded as defined elsewhere. For

'units"1'and 2 only, the backfeed is through the shutdown buses.

(shutdown buses do not serve unit 3) Backfeed svitches associated with each shutdown bus and 4160-V unit, boards A and 8, provide for trip and lockout of unit trans-former and start bus sources to the.

selected 4160-V unit boards, before closure of the selected 4160-V shutdown bus breaker vhich feeds the diesel generator power from the shutdown bus to the 4160-V unit

-board.

Alternate 2 Backfeed from shut-down boards Alternate 1 (c) 4 kV unit bd 3C Unit SS TR 3A Start bus 1A X-vinding 11 4 kV Common Board A Start bus 1A Unit SS TR 1A ~ .Autanatic delayed transfer from the X-winding normal to the alternate source is initiated by undervoltage on the normal source, subject to voltage check on the alternate source.

Automatic delayed transfer back to the normal source is initiated by return of normal voltage on the normal source. manual transfers in either direction are delayed type.

12 4 kV Common Board 8 Start Bus 18 Unit SS TR 2A, X~in ding

Cl 0'

Table 1 Auxiliary power Supplies and Bus Transfer Schemes - Sheet 7 Power Sources Item Board and/or Bain Bus Horma1 Alternate Reeaek" Alternate 1 13 4 kV Shutdown Board A Shutdown Bus 1 Shutdown Bus 2 (See also remarks for items 5 and 6.)

Alternate 2 Diesel generator A Alternate 3 manual, access con-nection to diesel generator 3A via 4-kV shutdown board 3EA Alternate 1 14 4 kV Shutdown Board B Shutdown Bus Shutdown Bus 2 Automatic delayed transfer from the normal to alternate 1 source is initiated by undervoltage on the normal source, and automatic return is initiated by normal voltage on normal source.- Automatic voltage transfers from normal to Alternate 1 are blocked in the presence of an accident signal.

Alternate 2 Diesel generator B Alternate 3

, Banual, access con-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.

After 5 seconds without voltage on the shutdown board, all its supply breakers and all its loads 4160-480-V transformers are 'xcept

Auxiliary

'Fable 8 3-1 Power Supplies and Bus Transfer Schemes - Sheet 8 0

Power Sources Item Board ~ndlor Bain Bus Normal Alternate Remarks automatically tripped. Alternate 2 source is then automatically connected. manual return to the normal auxiliary power system is permitted if normal auxiliary power system voltage returns and if a unit is not in early stage of accident.

Alternate 2 Diesel. generator-C Alternate 3 Banual, access to diesel generator 3C via 4-kV shutdown board 3 EC Alternate 1 16 4 kv Shutdown Board D Shutdown Bus 2 Shutdown Bus 1 Alternate 2 Diesel generator D Alternate 3 danual, access to diesel generator,3D via 4-kV shutdown board 3 ED Alternate 1 16a 4 kV Shutdown Board 3EA 4 kV Unit Board 3A 4 kV Bus Tie Bd Provision is made to manually select alternate 3 source.

Alternate 2 Diesel generator 3A Alternate 3 Banual, access to diesel generator 3D via 4-kV shutdown board A Alternate

Table 1 Auxiliary Pa'er Supplies and Bus Transfer Schemes Sheet 9 Power Sources Item Board and/or Bain Bus Bormal Alternate Remarks 16b 4 kV Shutdown Board 3EB 4 kV Unit Board 3A 4 kV Bus Tie Bd Provisions are included for backfeeding diesel generator power from 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, means are provided to manually synchronize 4-kV shutdown boards.

Alternate 2 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 hanual, access to diesel generator C via 4-kV shutdown board C Alternate 1 r

16d 4 kV Shutdown Board 3ED 4 kV Unit Board 3B 4 kV Bus Tie Bd Alternate 2 Diesel generator 3D Alternate 3 Banual, access to diesel generator D via 4-kV shutdown board 0

Auxiliary Pcwer Supplies

,0 and Bus Transfer Schemes Sheet 10 Pover Sources It~m Board and/or Bain Bus Sormal Alternate Resurk.

17 480-V Water Supply Board Alternate 1 (a) Bus 1 4 kV unit bd 1B Bus 2 (Item 17b) Automatic transfer from the normal via TR TH1 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 Bus 3 (Item 17c)

Alternate 1 (b) Bus 2 4 kV unit. bd 2B Bus 1 (Item 17a) via TR TQ2 Alternate 2 Bus 3 (Item- 17c)

Alternate 1 (c) Bus 3 4 kV unit, M 3B Bus 2 (Item 17b) via TR TQ3 Alternate 2 Bus 1 (Item '17a) 18 480-V Unit Boards Alternate 1 (a) Unit 1~ 480-V Unit, Bd 1A 4 kV unit M 1A 4 kVcomMB Automatic transfer from the normal via TR TU1A (via TR TEB) to the alternate source is initiated by time-undervoltage on the normal source Return to the normal source is automatic upon return of voltage to the normal source.

Alternate 1 (b) Unit 1, 480-V Unit Bd 1B 4 kV unit M 1B 4 kV corn bd B via TR TU1B (via TR TEB)

Alternate 1

0 Auxiliary Power Supplies and Bus Transfer Schemes - Sheet 11 0

Power Sources Ttem Board and/or Bain Bus Mormal Alternate Remarks (c) Unit 2, 460-V Unit Rd 2h 4 kV unit bd 2A 4 kVcombd 8 via TR TU2A (via TR TEB)

Alternate (d) Unit 2, 480-V Unit Bd 28 kV unit M 28 4 kV corn bd A via TR TU28 (via TR TEA)

Alternate 1 (e) Unit 3, 480-V Unit Bd 3A 4 kV unit bd 3A 4kVcomM A via TR TU3A (via TR TEll)

Alternate 1 (f) Unit 3, 480-V Unit Bd 38 4 kV unit bd 38 4 kV combd A via TR TU38 (via TR TEA) 19 480-V Lighting Boards (a) 480-V Lighting Bd 4 kV corn bd A 4 kVcomM 8 Transfer between sources is manual via TR TL1 (via TR TEB) only. Each 480-V lighting board serves as the power source, vi.a 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 kVcombd A 4 kV corn M 8 vi'a TR TL2 (via TR TEB)

(c) '80-V Lighting Bd 3 4 via kV corn bd 8 TR TL3 4 kVcomM A (via TR TEA) 20 *'480-V Common Boards (a) 480-V Common Bd 1 Bus A 4,kV corn bd A Bus 8 of Item 20a Automatic transfer from the normal via TR TC1A to the alternate source is initiated Bus 8 4kV corn M 8 Bus A of Item 20a by time-undervoltage on the normal vt.a TR TC18 source Return to the normal source is automatic upon return of voltage to the normal source.

(b)" 480-V Common Bd 2 Bus A 4 kV corn bd A Bus' of Item 20h via TR ~C2A 4kv corn bd 8 Bus 8 ot'tem 20h

Cl 0

Table huxiliary power supplies and Bus Transfer schemes - sheet 12 Power Sources Item Board and/or Bain Bus Hormal hlternate Remarks voa TR TC2E (c) 480-V Common Bd 3 Bus h 4 kVcombd h Bus 8 ot Item 20c via TR TC3h Bus 8 4 kV corn bd B Bus h of Item 20c via TR TC3B 21 480-V Service Building

!lain Board Bus h 4 kV corn bd h Bus B Same as remarks for Item 20.

via TR TSBh Bus B 4 kV corn bd B Bus h via TR TSBB 22 480-V Radwaste Boards Board 1 480-V Serv Bldg Bd 1) 480-V corn bd 1 If the normal feed should fail, a manually actuated transfer to the (item 21) 2) 480<<V Diesel hux Bd-h alternate source may be made.

Board 2 480-V corn bd 1 1) 480-V Serv Bldg Bd (item 21)

2) 480-V Diesel hux Bd-B 23 480-V huxiliary Boiler Bd Bus h 480-V corn bd 3 480-V corn bd 1 Both buses are normally fed from Bus B 480-V corn bd 3 480-V corn bd 1 source shown, and with the manually operated bus tie breaker closed.

hutomatic transfer of both buses from the normal to the alternate source

n'able 1 huxiliary Power supplies and Bus Transfer Schemes - sheet 13 Power Sources Its,m Board and/or Hain Bus Horma 1 h1 terna te Remarks is initiated by time-undervoltage 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 h 480-V shutdown Bd 1h 480-V corn bd 1 hutomatic Transfer from the normal Board B 480-V corn Bd 3 480-V shutdown Bd 38 to the alternate source if ini-tiated by time-undervoltage on the normal source. Return to the normal source 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 whi.le keeping the other bus section energized and in operation.

25 480-V Turbine 80V Boards (a) Unit 1, Board 1h 480-V unit bd 1h 480-V corn bd 1 hutomatic transfer from the normal to the alternate source is initiated by time-undervoltage on the normal source. Return to the normal source is automatic upon return of voltage to the normal source (b) Unit 1, Board 18 480-V unit M 1B 480-V corn M 2 (c] Unit 1 ~ .Board 1C 480-V unit bd 1B 480-V corn bd 2 (d) Unit 2, Board 2h 480-V unit bd 2h 480-V corn bd 3 (e) Unit 2, Board 2B 480-V unit bd 28 480-V corn bd 2 (f) Unit 2, Board 2C 480-V unit bd 2B 480-V corn bd 2 (g) Unit 3~ Board 3h ~ 480-V unit bd 3h 480-V corn bd 3 (h) 'nit 3> Board 3B 486-V unit bd 3B 480-V corn bd 3 (i). Unit, 3~ Board 3C 480-V unit bd 30 -480-V corn bd 2 26 480-V Condensate Demin-eralizer Boards (a) Unit 1 480-V unit bd lh 480-V shdn bd 18 In case of failure of the normal 4

source, automatic transfer is made to an energized alternate source.

huxiliary Power Table -1 Supplies and Bus Transfer Power Sources Schemes - sheet 14 I

Item Board and/or Bain Bus Norm- l alternate Remarks Upon restoration of the normal source, automatic return to normal is effected.

(b) Unit 2 480-V unit bd 2h 480-V shdn bd 28 (c) Unit 3 480-V unit bd 3h 480-V shdn bd 3B

Table Auxiliary Power Supplies and Bus Transfer schemes - Sheet 15 Power Sources Item Board and/or Bain Bus Ho rmal Alternate Remarks 27 480-V Reactor Building Vent Boards (a) Unit 1 ~ Board lA 480-V unit bd lA 480-V corn bd 1 See remarks of Item 24.

(b) Unit 1 ~ Board lE 480-V unit bd 1A 480-V corn bd 1 (c) Unit 2, Board 2A 480-V unit bd 2A 480-V corn bd 3 (d) Unit 2, Board 28 480-V unit bd 2A 480-V corn bd 3 (e) Unit 3 ~ Board 3A 480-V unit bd 3A 480-V corn bd 3 (f) Unit 3, Board 3B 480-V unit bd 3A 480-V,corn bd 3 28 480-V Turbine Building Vent Boards (a) Unit 1, Board 1A 480-V unit bd 1A 480-V corn bd 1 See remarks on Item 24.

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. The normally closed, manually operated bus tie breaker provides for main-tenance on one bus section while keeping the other bus section energized and in operation.

(b) Unit 1, Board 1B 480-V uni.t bd 1B 480-V corn bd 2 (c) Unit 2, Board 2A 480-V unit bd 2A 480-V corn bd 3 (d) Unit 2, Board 28 480-V unit bd 2B 480-V corn bd 2 (e) Unit 3, Board 3A 480-V unit bd 3A 480-V corn bd 3 (f) Unit 3~ Board 38 480-V uni.t bd 3B 480-V corn bd 2 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 TP TS1A via TR TS.1E alternate source is manual.

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

Auxiliary power Supplies and Bus Transfer Schemes - sheet 16 Power Sources Item Board ndlor Bain Bus Rormal Alternate Re asks (b) Unxt 1, 480-V Shutdown Bd 1B 4 kV shutdown bd C 4 kV shutdown bd B Remark (a) via TR TS1B via TR TS1E (c) Unit 2, 480-V Shutdown Ed 2h 4 kV shutdown bd 8 4 kV shutdown bd C Remark (a) via TR TS2h via TR TS2E Unit 2, 480-V shutdown Bd 28 4 kV shutdown bd D 4 kV shutdown bd C Remark (a) via TR TS28 via TR TS2E (e) Unit 3, 480-V Shutdown Bd 3A 4kV shutdown bd 3EA 4 kV shutdown bd 3EB Remark (a) via TR TS3h via TR TS3E Unit 3, 480-V Shutdown'Bd '3B 4 kvmhutdown bd 3EC 4 kV shutdown bd 3EB Remark, (a) via TR TS3B via TR TS3E 30 480-V Reactor NOV Boards Remark 29 (a)

(a) Unit. 1, 480-V Reac NOV Bd lh 480-V Shutdown Bd 1A 480-V Shutdown Bd 18 Remark 29(a)

(b) Unit 1, 480-V Reac BOV bd 18 480-V Shutdown M 1B 480-V Shutdown Bd 1h Remark 29(a)

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

(d) Unit 1 ~ 480-V, Reac BOV Bd 1D 480-V Shutdown Bd 1A 480-V Shutdown M 18 Automatic transfer from the via BG set via BG 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 NG sets.

(e) Unit 'l

~ 480-V Reac BOV Bd 1E 480-V Shutdown Bd 18 480-V Shutdown Bd 1h Automatic transfer from the normal via BG 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 of voltage to the normal source.

Isolation between normal and alternate is provided by BG sets.

(f) Unit 2, 480-V Reac BOV Bd 2A 480-V Shutdown Bd 2h 480-V Shutdown Bd 28 Transfer from the normal to the alternate source is manual. Inter-locks prevent transferring a fault from one source to another and paralleling sources.

(g) Unit 2, 480-V Reac NOV Bd 28 480-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 s'ource to another and paralleling

Table 8.

huxiliary Power Supplies and Bus Transfer Schemes - Sheet 17

-Power Sources Item Board and/or .'fain Bus !formal hlternate R>>>>kk>>

sources.

(h) Unit 2, 480-V Reac 50V Bd 2C 480-V Shutdown Bd 28 480-V Shutdown Bd 2h Transfer from the normal to the alternate source is manual. Inter-locks prevent transferring a fault from one source to ar.other and paralleling sources.

Unit 2, 480-V Reac 50V Bd 2D 480-V Shutdown Bd 2h 480-V Shutdown Bd 28 automatic transfer fro.. the normal via llG set via 5G set 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. Iso/ation between normal and alternate is'rovided by M sets Unit 2, 480-V Reac 50V Bd 2E 480-V Shutdown Bd 2B 480-V Shutdown Bd 2h hutomatic transfer from the normal via 5G set via 5G set to the alternate source is initiated by time-undervoltage cxf the normal source. Return to the normal source is manual upon return o voltage to the normal source. Isolation between normal and alternate is provided by 5G sets (Ic) Unit 3, 480-V Reac 50V Bd 3h 480-V Shutdown Bd 3h 480-V Shutdown Bd 38 Transfer from the normal to the alternate source is manual. Inter-locks prevent transferring a fault from one source to another and paralleling sources Unit 3, 480-V Reac 50V Bd 3B 480-V Shutdown Bd 38 480-V Shutdown Bd 3h Transfer from the normal to the alternate source is manual. Inter-locks prevent. transferring a fault from one source to another and paralleling sources.

(m) Unit 3, 480-V Reac 50V Bd 3C 480-V Shutdown Bd 38 480-V Shutdown Bd 3h Transfer from 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 50V Bd 30 480-V Shutdown Bd 3h 480-V Shutdown Bd 3B hutomatic transfer from the normal to via lfG set via 5G set the alternate source is initiated by time-undervoltage on the normal I source. Return to the normal source I is manual upon return to voltage to I I

the normal source.'solation between normal and alternate is provided by 5G sets

Auxiliary

.able 8. 1 power Supplies and Bus Transfer Schemes - Sheet 18 0

Power Sources Board andlor Bain bus sormal. Alternate Remarks (o), Unit 3, 480>>V Reac BOV Bd 3E 480-V Shutdown Bd 38 480-V Shutdown Bd 3h Automatic transfer fro-.the normal via HG 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 BG sets 31 480-V Diesel Auxiliary Boards (a) 480-V Diesel Aux Bd A 4 kV Shutdown Bd h 4 kV Shutdown Bd 8 I'ransfer from the normal to the via TR TDh via TR TDE alternate source is manual. Inter-locks prevent transfe ring a fault from one source to and paralleling sources. another (b) 480-V Diesel hux Bd 8 4 kV Shutdown Bd D 4 kV Shutdown Bd 8 Remark (a) via TR TDB via TR TDE (c) 480-V Diesel lux Bd 3EA 480-V Shutdown Bd 3h 480-V Shutdown Bd 3B Remark (a)

(d) 480-V Diesel Aux Bd 3EB 480-V Shutdown Bd 38 480-V Shutdown Bd 3A Remark (a)

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.t Key Diagram of Normal and Standby IS>>$ (0.1 4 Auxiliary Power System - Unit 3 ECIV PCQIS ADO VSS CRJSTSCS XFVRANDRETIJRH TO 5VFERSECf CRIAKTNCS ccwllcr/IIATIDN<<RXE l54500-I RS 4 ISNI500.2 IVA ECN P 008( AND 0)J P co/4 Jr>>STALL CEJIERAIQR SIIRS FIGURE 8.3-2 IwsrfCT(0 NO JPPNDJ( 0 FOR Issrrf KNOXVILLE Cr E 15W500 3

I T

ENCLOSURE 3

SECTION 1 RESPONSE TO APRIL 8, 1980, LETTER FROM T. A. IPPOLITO TO H. G. PARRIS-

"REQUEST FOR ADDITIONAL INFORMATION BROWNS FERRY UNITS 1, 2, AND 3 DEGRADED GRID VOLTAGE" QUESTION 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, I

and allowable values for second level undervoltage monitors.

Staff position 3 states the criteria for testing requirements.

Enclosure 2 of our June 3, 1977 letter shows all the criteria of staff positions (1)(f) and 3 in Model Technical Specification (MTS) 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.

RESPONSE

(See proposed technical specifications.)

QUESTION 2 Staff position (1) (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) seismic and environmental qualification, (2) class 1E qualifications, (3) independence, (4) redundant, (5) reliaibility, and (6) testabilityland others pertinent to the design.

RESPONSE

Re uirements of IEEE 279-1971

1. Seismic and Environmental ualifications 2

The voltage monitors will be operable under seismic conditions:

(a) These relays (I-T-E type 27H and 59H) have been seismically qualified to a'more severe seismic level at other plants than that required for Browns Ferry Nuclear Plant.

(b) The Agastat relays, types E7012 and E7022, are seismically qualified for these specific applications by combination of seismic and circuit analysis. The analysis compared the most pessimistic seismic requirement imposed on the relay at their mounting locations with the relay seismic capability established I

by vendor-supplied test data.

(c) All equipment will be located above probable maximum flood level. Monitors will be I

mounted inside switchgear and are designed to operate under accident conditions with temperature range from -30'C to +70'C.

2. Class lE ualifications All equipment is Class 1E. Voltage monitors are ITE type 59H overvoltage and type 27H undervoltage solid state relays. The relays are arranged in a two out of three logic for each voltage condition; therefore, I

the failure of a sipgle voltage monitor will not cause the system to be inoperable. All voltage monitors will be mounted in the shutdown system switchgear w ich 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 f fI f

Each 4-kV shutdown board is supplied with three overvoltage and three undervoltage monitors. Each system of three monitors is connected so that a single failure will not result in the loss of the appropriate tripping function.

5. Reliabilit of Com onents Components used to monitor degraded grid voltage conditions have been selected to ensure voltage f

monitoring system operation. These components comply with the quality control 1

and assurance requirements as set forth in 10 FR Part 50.

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

QUESTION 3 Provide sufficient information (voltage drop analyses) to allow our independent verification that the undervoltage protection 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 transien't (e.g., unit trip) or an accident, whichever presents the largest load demand.

RESPONSE

The 4-kV shutdown board degraded voltage relaying initiates a transfer of the shutdown board to the standby onsite (diesel) power distribution system when the board steady state voltage fails to stay within a voltage range which will ensure proper operation of all safety loads fed from the board. Standard motor designs require a voltage range of +10 percent of their rated voltage for running and a minimum of 85 percent voltage for starting.

In establishing the degraded voltage points, an inhouse computer program ( -VSP -

) was used to perform the calculations for all sources of offsite power. The summary sheets for the computer studies (NIMV 2p 6y 7~ 10'ip 12 15'5A 15B 16 17 17A 17B 18'9

20) are attached. To simplify analysis a minimum of one percent and a ma'ximum of five percent steady state voltage drops to the 480-V loads was assumed.

Summary sheet NINV2 shows the shutdown board voltage for unit. and 1

2 when supplied from the 500-kV offsite power circuit. A system voltage at 490-kV and the unit station service transformer on-load tap in the zero boost position were used for this study and a "worst case" load (LOCA in unit 1 and a full load rejection of unit 2). An acceptable voltage can be maintain<.d for these conditions. The on-load tap changer has an adjustment range of + 10 percent which maintains an acceptable shutdown board voltage for anticipated swings in the 500-kV grid.

To determine the lower degraded voltage setting, 4-kV shutdown board A, and its associated shutdown board 480V were studied under "worst case" conditions (fed from minimum voltage 161-kV switchyard, all 4-kV motors running, unit and shutdown board 480V transformers fully loaded).

Computer runs NINV15 16, 17 and 18 show these cases.

. 4-kV shutdown board A was chosen because this board feeds the largest 480Y motors - the 205 HP control bay water chill'er on 480Y'shutdown

'oard 1A, and the 40 HP core spray inboard valve on 480V reactor HOV board 18. A study qf this system will represent'he auxiliary power system's worst case.

NIIIV16 verified the proper operation of the 4-kV auxiliary power system The steady s'.ate 4-kv shutdown board A voltage was determined to be 676gv with the 161-)V switchyard operating at 167-kV.

x NIMV16 17 and 18 assumed 3769V on 4-kY shutdown board A and evaluated the 480V system for 480Y transformer tap settings at normal,2.5 percent boost,and 5.0 percent boost. With the 480V r

transsormer set on 5 percent boost tap ~NINV'l7), the 460V sps em operated properly and allowed for a 5 percent cable voltage drop to each load.

Both the control bay water chiller and the core spray inboard valve motors started successfully under worst case conditions.

The results of the 4-kV shutdown board A examination are:

(1) The 4160-vol) shutdown board minimum voltage was 3769V.

(2) The 480-vol]. transformer tap changer should be set 'on the 5 percent boost.

(3) Under conditions {1) and {2):. the safety. loads have adequate n

~

voltage to start and operate properly; and the 480V shutdown boards have a minimum voltage of 438V, which is greater than

'5 percent of 460Y (motor-rated'oltage).

Before using 3769Y as the lower degraded voltage setting, the possibility of maintaining this voltage at the unit 3, 4160V shut-down boards was studied (NINY 12, 19, and 20). Voltage can be maintained at 3782V at the unit 3,. 4160V shutdown boards under worst case loadiI)g conditions if the 161-kY switchyard maintains at least 160-kV yoltage.

1 Therefore, 3807 volts (3769Y + 1 percent relaying tolerance) was selected as the degraded voltage low set-

)

point at the 4160V shutdown boards. 161-kV grid voltages below 160-kV will be annunciated.

Summary sheet NINV15 shows the results of the studies used to determine the upper degraded voltage set point. A set point of 4400 volts has been chosen. A relay tolerance of + one percent gives a range of, 4444 maximum and 4356 minimum. This is the voltage

at the shutdown board bus. Considering voltage drop in a motor cable, the voltage at a 4000-volt motor will be acceptable. This results in a voltage on the 400-volt shutdown board of approximately 521 volts (1'l3 percent of 460 volts). This is considered acceptable for the frequency and duration that the electric distribution system is expected to be in the assumed configuration and since cable impedance would further reduce the voltage at the motor terminals. The normal source of power for the safety related and non-safety related auxiliaries will be from the main generator through the unit station service

.transformer (USST) if the generator is synchronized to the system or from the 500-kV system if the main generator is isolated by the generator breaker. The USST's have automatic on-load tap changers which will maintain a voltage on the. shutdown board at approximately 4160 volts. The safety and non-safety auxiliaries are expected to be supplied from the 161-kV grid only for a fault on equipment making up the 500-kV offsite circuit (USST, isolated bus, main transformer, etc.) or to perform maintainance on the items during a refueling outage. The percentage of time is estimated to be approximately 5 percent or less. The possibility of maximum grid voltage and minimum load occuri~g at the same time further reduces the exposure time. 161-kV grid voltages d

above 170-kV will be annunciated.

The minimum degraded voltage relay pickup time plus time delay will

'be approximately 8-1/2 seconds before transferring safety buses to the standby diesels for a degraded voltage condition, The relay has an instantaneous reset for return of voltage above the relay setpoint.

The worst case condition concerning motor startup, board transfer, etc.

would be a LOCA occurring simultaneously with the loss of a 500-kV

0' h,

preferred offsite source. Under this condition, within 4-1/2 seconds the 4-kV shutdown boards would transfer to an alternate source. The board motors would take a maximum of 0 seconds to start after board voltage is restored. This allows a reset of the degraded voltage relay before transferring safety buses to'the standby diesels, thus I

E preventing spurious separation of safety buses from 1

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~/Al V I /v/p1vX 0 grrdPC Q,r. +Allo OCr c'R ZOn r7 ~/CL br dr a/2 338/ V(84.$7rdr4rrr>) 3C S S V ( SS <>i ri 4rrrv) g~rc2 roo ~> n. 5/i roun 4/7 ~ ~ grf V(gkd)dr/ S/Crr) SSC3 v (812/r r S C ") 7/rS nZSrs~ /S g nc Oc rl 7S 5l En p) 'Sl n J-E Voc 7n CE rare c n N/wv zo SE'rrr ~/u V /P R 2C /) V Ar.) 7r de So v ) 371c 4 ( 4 S.S7r rF 4r~v) ~I/~I-A/Ar 4 crEnn) gr+ rg 5// t oa rr 4 O 2 c/1 v (S2 do rr 4/cd v ) 7 /8'C+ ( 9r 1 Fy rd 4/Crv) pd ar eS'rC~v '(37~'-y) l a 5wcn 37 s 1 v (gr. gl~ dr 4/sd" ) 3 82CV ( qg,rprd </Crv) 4 d'rir~6 CVOn'C e, n 54: 4<rt O/~4r CT SwCR t) A 31@ / V( fJ. g Jrrrc4ICSV 3'TCOV ( Ss.24 rr 4/~") i r/</6/ h. v ~ err r/-C h Yn F 4 Voc pnGC-- rf./uS g pc g g Z4 nial rc'DA-C . bl'i'RrlhrD Vis.gird <<//C /. Eg yEl lt,l aÃa I V. 'C 0 0 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: Confirm the acceptability of the voltage conditions on the station electric distribution systems with regard to both (1) potential overloading due to transfers,to either safety or nonsafety loads, and (2) potential starting transient problems in addition to the concerns expressed in our June 2, 1977, correspondence with'egard to degraded voltage conditions due to conditions origipating on the grid. Specifically:, QVESTION 1 Figure 1 shows that one shutdown bus (Board) can have power supplied from a second shutdown bus. If nothing prohibits such a connection, should be analyzed for all three units as NRC guideline 1 requires. e REFERENCE e 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 transient (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

I Units 1 and 2 shutdown /uses can be supplied from either of the preferred offsite sources (500-kV system or 161-kV system). Analysis has been made for the loads of unit 1 in LOCA and unit 2 in a foll load rejection (which is the worst case loading) supplied from unit station service transformer (USST) 1B which connects to the generator bus through the main transformer to the 500-kV system which is the normal preferred offsite power source.

.Analysis has been made for this same .worst case loading when supplied through the common station service transformer (CSST) from thc 161-kV preferred offsitc power source. Scparatr <<na)ysis is not provided for unit 2 USST or CSST supplying thc same loads, since it would bc an identical analysis to that provided for unit 1.

Unit 3 has been analyzed for the LOCA loading (which represents the worst case loading) 'when the shutdown buses are powered from USST 3B which connects to the generator bus an) through the main transformer to the 500-kV preferred l

offsite power source. An analysis was also made for this same loading when the, safety buses are powered from the 4-kV bustie board which connects through the cooling tower transformer to the 161-kV preferred offsite power source The circuit to each unit (main transformer, generator bus, USST) from the 500-kVsystcm is considered a separate preferred offsitc source to that unit. Based on the syst'm design, two units are the maximum that will be connected to the CSST's at any onc time. Otherwise we assume a complete loss of offsite power aqd each unit's safety loads will be powered from the onsite sources (standby diesels).

A ncparntc <<nnlysis ia not piovid< d lor unit

~

3 Jlowcrcd flolll the CSS'i'a Lh<.-

loading would be similar to thc analysis for the unit 1 LOCA and unit 2 full load rejection.

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. Ippolito 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.

question

2. With the addition of generator low-side breakers and (automatic?)

d tap-changing station service transformers (Items 4, 5 ), another possible power source to the class 1E buses is established. Per NRC guideline 1 , this should be analyzed for all three units.

Reference 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 transient (e.g., unit trip) or (2) an accident, whichever presents the largest load demand situation.

R~es onse See response to question 1 in this series of questions.

question

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

class 1E 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 equipment rated to operate with the analyzed voltages without blowing fuses, overheating, etc., and without affecting the equipments'bility to perform the s

required function?

R~es onse For voltages at the 480-V'uses, see the response to questions 3 of the April 8, 1980 request for additional information. The voltage was calculated for the buses with the worst case loads, and largest motors, and proved adequate; thus other buses with lesser loads, smaller motors, and shorter feeder cables are assumed to b~ adequate.

Separate analysis for bpses less than 480-Vwill be submitted at a later

uestion

4. The ENGINEERED SAFETY FEATURE ACTUATION SYSTEM INSTRUMENTATION TRIP VALUES table shows that a +5 percent tolerance is allowed on 3920V b

(95 percent of 4160V) set point (figure 1 ). Positive 5 percent tolerance will cause spurious trip of offsite power (NRC Guideline 12 ) whereas the negative 5 percent tolerance will cause unacceptable e

voltages .on equipment on 480V and below (NRC guidelines 10 ) Justify' I

the proposed tolerance band or provide new values.

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

12 . Voltage-time settings 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 operation of electric loads.

~Res esse This questions refers specifically to the plant as now configured.

Information in response to this question is furnished as part of the repsonse to questions 3 of the April 8, 1980, NRC request for additional information.

ucstion

5. The TVA references do not define the minimum and maximum anticipated e

grid voltages. Guideline 6 allows three methods of determining the valu<: of the degrade<i grid voltage, which<.vcr provides the worse case.

TVA should <tcscril><. ltow their gri<l volt.ag< levels <<r<<tct.cnnin<<; 1 (nne method mny produce I:hc low voltage while another method may produce the high voltage) apd state what these values are.

Reference 6 . The voltage at the terminals of each'safety load should be calculat:ed base<I on thc above listed consi<lcrations and assumpt.inns an<I based on the assumption that the grid voltage is at the "minimum expected value." The "miminum expected value" should be selected based on rhe least of the following:

a. The minimum st<;ady-state voltage experienced at the connection to the offsite circuit.

b. Thc minimum voltage cxpcctc<l at t.hc connection to thc offsit.e circuit <lu< ~ t.o cont.ing<.ncy plans which may result in rcducc<1 volt.ag<. from t ilia gri<l.

II

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

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 the 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 cohtingency plans. The 500kV grid maximum voltage will be 550kV (110 percent of 500kV) based on contingency plans.

3 I s 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.

e

~

guestion 6.- Per NRC guidelines 3 and 9 , compare the effect of starting and running' a 8000-HP reactor recirc. M-G set on all class 1E buses and loads with the required voltage range for normal operation of these class 1E loads (starters, contactors, motor ratings, .etc.). What are the bus and load voltages yhen starting the largest 480V class lE load when, 1

all class 1E buses are otherwise fully loaded?

References 3 . All actions the electric power system is designed to automatically initiate should be assume'd 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 s

voltage require immediate remedial action and notification of NRC.

i

~Res onse The 8000-HP reactor recirc., M-G set is powered from a separate USST during normal operation and will have no effect on the voltages to the class 1E buses.

The 8000-HP reactor recirc., 11-G set will not be running when a unit is being shutdown from the CSST.

I'or bus and load voltages when starting the largest 480V class lE load when all class 1E buses are fully loaded see the response to question 3'of the

)

April 8, 1980 request for additional information.

~ ~

guestion e

7. NRC guideline 11 , which asks for a determination of the maximum voltage expected at each safety load (and starting circuit), has not been supplied by any of the TVA references. TVA should supply this 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 I

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 immediat~ remedial action is required and NRC shall be notified.

~Res onse See the response to question 3 of the April 8, 1980 request for additional information.

question S. The TVA references have not provided a separate analysis for each e

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 7P.

References 2 . For multi-unit stations a separate analysis should be performed for each unit assuming (1) an accident 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.

r 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 See response to question 1 in this series of questions.

guestion e

9,. The NRC requires (page 2, paragraph 3 ) verification of the analysis method and parameters. The TVA 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 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.

~Res 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:

C 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 will be calculated for the above boards using the same computer-assisted methods as used in the worst case conditions calculations. Acceptance criteria for I

comparing the calculated voltages with measured voltages will be established after test accuracy of peters 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 se vice transformers.

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10. The NRC requested (page 2, paragraph 4 ) that the TVA review the Browns Ferry electric power systems to determine if potential violations of GDC 17 existed. The TVA references did not contain the 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:

En addition, you are requested to review the electric power systems of your nuclear station to determine if there 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 be completed, and a popy 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 GDC-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 line

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reIaying and thel61-kV switchyard equipment is supplied from the same battery board. (When the undervoltage modification is installed, the 500-kV 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 the next two years,and the 161-kV switchyard and line relaying I

will be transferred to this new battery system.

.P REFERENCES

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

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

c~ 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.

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

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

TVA letter L. M. Mills to Director of Nuclear Reactor Regulation, NRC, Docket Nos. 50-259, -260, -296, dated September 4, 1979.

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