ML20032B181
| ML20032B181 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 09/30/1981 |
| From: | Udy A EG&G, INC. |
| To: | Bajwa S Office of Nuclear Reactor Regulation |
| References | |
| CON-FIN-A-6429 EGG-EA-5433, NUDOCS 8111050080 | |
| Download: ML20032B181 (12) | |
Text
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EGG-EA-5433 SEPTEMBER 1981 P44 ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM
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This is an informal report intended for use as a preliminary or working document i
l Prepared for the d.S. Nuclear Regulatory Commission Under DOE Contract No. CE-AC07-76ID01570 0
g g g g,,,n, FIN No. A6429 YD 8111050080 810930 PDR RES 8111050080 PDR
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FOEM EGSG 398 (Rev.11714 INTERIM REPORT Accession No.
Report No. EGG-EA-5433 Contract Program or Project
Title:
Selected Operatino Reactor Issues Program (III)
Subject of this Document:
Adequacy of Station Electric Distribution System Voltages, Big Rock Point Plant, Docket No. 50-155, TAC No. 12781 Type of Document:
Informal Report Auth r(s):
A. C. Udy D:t2 of Document:
September 1981
- R:sponsible NRC Individual and NRC Office or Diilsion:
S. S. Bajwa, Division of Licensing This document was prepared primarily for preliminary orinternal use. it has not received full review and approval. Since there may be subt'antive changes, this document should not be considered final.
EG&G Idaho, Inc.
Prepared for the U.S. Nuclear Regulatory Commission Washington, D.C.
Under DOE Contract No. DE AC07-761D01570 NRC FIN No.
A6429 INTERIM REPORT
L 0380J 4
ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES BIG ROCK POINT PLANT Docket No. 50-155 September 1981 A. C. Udy Reliability and Statistics Branch Engineering Analysis Division EG&G Idaho, Inc.
i Draft 9-18-81 TAC No. 12781
r ABSTRACT The Nuclear Regulatory Commission has required all licensees to analyze the electric power system at each nut aar station. This review is to deter-i mine if the onsite distribution system in conjunction with the offsite power sources has sufficient capacity and capability to automatically start and operate all required safety loads within the equipment voltage ratings.
This Technical Evaluation Report reviews the submittals for the Big Rock Point Plant.
The offsite power sources, in conjunction with the onsite distribution system, has been shown to have sufficient capacity and capability to auto-matically start as well as continuously operate, all required safety-related loads within the equipment rated voltage limits in the event of eitner in anticipated transient or an accident condition.
FOREWORD O
This report is supplied as part of the " Selected Operating Reactor Issues Program (III)" being conducted for the U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation, Division of Licensing, by EG&G Idaho, Inc., Reliability and Statistics Branch.
The U.S. Nuclear Regulatory Commission funded the work under the authorization, B&R 20 19 01 06, FIN No. A6429.
9 r
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CONTENTS 1.0 I N TR O D UC T I O N....................................................
1 2.0 DESIGN BASIS CRITERIA...........................................
i 3.0 SYSTEM DESCRIPTION..............................................
2 4.0 ANALYSIS DESCRIPTION........................
2 4.1 An a l ys i s C on d i t i on s.......................................
2 4.2 Analysis Recults..........................................
2 4.3 An a l ys i c /e r i f i c at i on.....................................
2 5.0 EVALUATION......................................................
4
6.0 CONCLUSION
S.....................................................
5
7.0 REFERENCES
6 FIGURE 1.
Big Rock Point electrical single-line diagram...................
3 TABLES 1.
Class IE Equipment Voltage Ratings and An alyzed Wors t Case Load Terminal Voltages......................
4 2.
Comparison of Analyzed Voltages and Undervoltage Relay Setpoints....................................
6 iii
l l
ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES l
L BIG ROCK POINT PLANT
1.0 INTRODUCTION
An event at the Arkansas Nuclear One station on-September 16, 1978 is described in NRC IE Information Notice No. 79-04. As a result of this event, station conformance' to General Design Criteria (GDC).17 'is being.
questioned at all nuclear power stations. The NRC, in the generic letter of Auguyt 8,1979, " Adequacy of Station Electric Distribution Systems Volt-ages,"'
required each ' licensee to confirm, by analysis, the adequacy of the voltage at the class lE loads. This letter included 13 specific guide-lines to be followed in determining if the load terminal voltage is adequate to start and continuously operate the class lE loads.
Consumers Power Conpany (CPCo) resporded with letters dated February 19, 1930,2 and August 29, 1980.3 CPCo supplied further information requested'for this review on March 23, 1981.4 CPCo correspondence of June 14, 1978,5 August 21, 1980,6 and December 12, 1980,7 were also reviewed for this report. Additional clarifications were submitted on May 4, 19818 and August 26, 1981.9 Based on the information supplied by CPCo, this report addresses'the capacity and capability of the onsite distribution system of the Big Rock Point Plant, in conjunction with the offsite power system, to maintain the voltage for the required class lE equipment within acceptable-limits for the worst-case starting and load conditions.
2.0 DESIGN BASIS CRITERIA The positions applied in determining the acceptability of the offsite voltage conditions in supplying power to the class lE equipment are derived from the following:
1.
General design Criterion 17 (GDC 17), " Electrical Power Systems,"
of Appendix A, " General Design Criteria for Nuclear Power Plants,"
of 10 CFR 50.
2.
General.Desiga Criterion 5 (GDC 5), " Sharing of Structures, Sys-tems, and Components," of Appendix A, " General Design Criteria for Nuclear Power Plants," of 10 CFR 50.
3.
General Design Criterion 13 (G0C 13), " Instrumentation and Con-trol," of Appendix A, " General Design Criteria for Nuclear Power Plants," of 10 CFR 50.
4.
IEEE Standard 308-1974, " Class lE Power Systems for Nuclear Power Generating Stations."
5.
Staff positions as de dated August 8,1979.{ ailed in a letter sent to the licensee, 1
6.
ANSI C84.1-1977,.' oltage' Ratings for Electric Power Systems and Equipment (60 Hz)
Six review positions;have been established from the flRC analysis guide-
-linesi and the above-listed documents. These positions are stated in Section 5.0.
3.0 SYSTEM DESCRIPTION Figure 1 of this report is a simplified. sketch of the unit single-line diagram of the Big Rock Point power distribution system.
It is taken from Attachmer.t 15 and Figure 1.3 The Big Rock Point station has a single class lE Motor Control Center (MCC-28) which is normally powered by MCC-2A from Load Center 2 via 2400V/480V transformer No. 22.
Transformer No. el, Load Center 1, and MCC-1A can also supply MCC-28. Both transformer No 11 and transformer No. 22 are energized by the same 2400V switchgear which is supplied by transformer No. 1 (from the unit generator on the 138kV grid) or by the 46kV grid via a voltage regulating transformer with either source.
.ll5V instrument and control panels are supplied from either MCC-1A or MCC-2B.
4.0 ANALYSIS DESCRIPTION
^
4.1 Analysis Conditions. CPCo has determined that the minimum expec-ted offsite grid voltage is 95% of nominal, and that the maximum grid volt-age is 103.6% for the 138 kV grid and 97.2% for the 46 kV grid.
CPCo has analyzed each offsite source to the onsite distribution system-under extremes of load and offsite. voltage conditions to determine 'the terminal voltages to the class IE equipment. The worst case class lE egaipment terminal voltages occur under the following conditions:
1.
The minimum expected continuous load terminal voltage.for a class lE load occurs-when either the unit generator voltage is at its minimum with full-unit loads or the 46kV grid is at its mini-mum with normal unit loads.
2.
The minimum expected transient load terminal voltage for a class lE load occurs when the~138kV grid is at its mi.nimum, normal unit loads are running and the 1500 hp reactor feed pump is' started.
l 3.
The maximum expected continuous load terminal voltage for a class lE load occurs when the unit generator voltage is at its maximum value and the unit loads are at a minimum.
4.2 Analysis Result. Table I shows the projected worst case class lE equipment terminal. voltages.
4.3. Analysis Verification. CPCo has verified the accuracy of the analysis for the Big Rock Point Plant by comparing voltages obtained by an 2
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TABLE 1.
CLASS lE EQUIPMENT V0LTAGE RATINGS AND ANALYZED WORST CASE TERMINAL VOLTAGES (% of nominal voltage)
Maximum Minimum Analyzed a
Equipment Ccndition Rated Analyzed Rated Steady State Transient 80
'82.0b 440V Motors Start Operate 110 109.7 90 90.4b ll5V Instru.
Operate 108.7 101.l' 93.0 93.2c and Controls 480V Starters Pickup 85 76.6 65 76.6 Dropout Operate 125 100.5 85 88.0 a.
Bus voltage supplied by CPCo. Assuming no feeder. voltage drop, the load terminal voltage would be the same.
b.
CPCo supolied bus voltage minus the CPCo supplied worst. feeder voltage drop (1.5%).
c.
This voltage takes credit for operation of the 2400V voltage regulating transformer. All other analyzed voltages shown do not take credit for the operation of the voltage regulating transformer.
oscilligraph with analyzed voltates for the same condition (i.e., steady state and startup of the 100 hp fire pump on MCC-28.) The test showed the analysis to be within the accuracy limits of the instrumentation used.
5.0 EVALUATION yixreviewpositionshavebeenestablishedfromtheNRCanalysisguide-and the documents listed in Section 2.0 of.this report. Each-lines review position is stated below followed by an evaluation of the licensee submittals.
Position 1--With the minimum expected offsite grid voltage and maximum load condition, each offsite source.and distribution system connection combination must be capable of startirg and of continuously operating all class lE equipment within the equipment voltage ratings.
CPCo has shown, by analysis, that the Big Rock. Point Plant has sufficient capability and capacity for continuously operating the class lE loads-within the equipment voltage ratings (Table 1).
4
Position 2--With the maximum expected offsite grid voltage and minimum load condition, each offsite source and distribution system connection combination must be capable of continuously operating the required class lE equipment without exceeding the equipment voltage ratings.
CPCo has shown, by analysis, that the voltage ratings of the class lE equipment will not be exceeded.
Position 3--Loss of offsite power to either of the redundant class lE distribution systems due to operation of voltage protection relays, must not occur when the offsite power source is within expected voltage limits.
As shown in Table 2, voltage.rclays will not :ause the loss of the class lE distribution system when the offsite grid ioltage is within expected voltage limits.~ Big Rock Point does not have a redundant clcss lE distribution system.
Position 4--The NRC letterI requires that test results verify the accuracy of the voltage analyses supplied.
CPCo has verified, by tes+, the validity of the anaysis for the Big Rock Point Plant.
Position 5--No event or. condition sr.ould result in the simultaneois or consequential loss of both required circuits from the offsite power network to the oncite distribution system (GDC 17).
The Big Rock Point unit does not conply with GDC.17 tince it has a single 2400V hos between redundent offsite grids to the single 480V class lE-distribution system. The NRC will exanine this fully in the Systematic Evalaation Program, Topic VII-3, Safe Shutdown.
Position 6--As required by GDC 5, each offsite source shared between units in a multi-unit station murt be capable of supplying adequate starting and operating voltage for all required classolE loads with an accident'in one unit and an orderly shut <iown and cooldown in the remai,1ing units.
This applies to multi-uqit. plants.
It d,oes got apply to Big Rock Point, a single-unit st3 tion.
6.0 CONCLUSION
S The voltage analyses submitted by CPCo for Big Rock Point were evalu-ated in Section 5.0 of this report.
It was found that:
1.
Voltages within the operating limits of the class lE e~quipment are supplied for all projected combinations of plant load and offsite power grid co,nditions.
t 2.
The test used to ferify the analysis shows the analyses to be an accurate represeritation of the worst case conditions analyzed.
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TABLE 2.
COMPARISON OF ANALYZED VOLTAGES AND UNDERVOLTAGE RELAY SETP0INTS
(% of nominal voltage)
J a
Minimum Analyzed Relay Setpoint i-Location / Relays Voltage Time V_oltage (Tolerance)
Time I
2400V bus Degraded grid 93;2 continuous 90.1 (+0.9) 10.55s
(+0.55s)9
-480 V bus t '
Lass of grid 76.6b 5 s.
'ess than or equal instantan-o or less to 50 eous
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a.
Licensee has determined by analysis the minimum bus voltages with the l
offsite grid at the minimum expected voltage and the worst case plant and 1
class lE loads.
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b.
For start of 1500 hp reactor feed pump, this produces the most degraaed voltage for the undervoltage relays.
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.l 3.
CPCo has determined that no potential for either a simultanous or consequential loss of both offsite power sources exists. However, there are portions of the Big Rock Point distribution system r.
where a single failure can negate both sources.
This will be
-examined as part of Topic VII-3 of the Systematic Evaluation j
i'rogram.
4.
Loss of offsite power to class lE buses, due to spurious operation f
of voltage protection relays, will not occur with the offsite grid voltage within its expected limits.
l
~ 7'O REFERENCES i
l.
NRC letter, William Gammill, to All Power Reactor Licensees (Except Humboldt Bay), " Adequacy of Station Electric Distribution Systems Voltage," August 8,1979.
5 2.
'CPCo letter, David P. Hoffman, to Director, Nuclear Reactor Regula-tion, NRC, " Adequacy of Station Electric Distribution Systems Volt-
+
ages," February 9, 1980.
3.
CPCc letter, David P. Hoffman, to Director, Naclear Reactor Regula-tion, NRC, " Adequacy of Station Electric Distribution Systems Volt-ages," August 29, 1980, J
g il 4._
CPCo letter, David P. HclTman, to Director, Nuclear Reactor Regula-tion, NRC, " Adequacy of Station Electric Distribution Systems Volt-ages," March 23, 1981.
6
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5.
CPCo letter, William S. Skibitsky, to Director, Nuclear Reactor Regulation, NRC, "On-site Emergency Power SoJrces," June 14, 1978.
6.
CPCo letter, David P. Ho.iman, to Director, Nuclear Reactor Regula-tion, NRC, " Degraded Grid Voltage," August 21, 1910.
7.
CPCo letter. David P. Hoffman, to Director, Nuclear Reactor Regula-tion, NRC, " Response to Request for Additional Information Related to the Generic Issue on Onsite Power Systems," December 12, 1980.
8.
CPCo letter, Gregory C. Withrow to Director, Nuclear Reactor Regulation, NRC, " Generic Issue--Adequacy of Station Electric Distribution Voltages," May 4,1981.
9.
CPCo letter, David P. Hoffman to Director of Nuclear Reactor Regulation, NRC, " Station Electric Distribution System Voltages and Degraded Gria Protection," August 26, 1981.
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