ML20054M714
| ML20054M714 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 06/30/1982 |
| From: | Udy A EG&G, INC. |
| To: | Prevatte R Office of Nuclear Reactor Regulation |
| References | |
| CON-FIN-A-6429 EGG-EA-5891, NUDOCS 8207140283 | |
| Download: ML20054M714 (12) | |
Text
_
EGG-EA-5891 June 1982 N4 ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM gg
- 6 VOLTAGES, BIG ROCK POINT PLANT Drts Of s.
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Prepared for the U.S. Nuclear Regulatory Commission Under DOE Contract No. DE-AC07-761D01570 FIN No. A6429 EGr5,o n.
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f OHu (G4G ym isa,03pa INTERIM REPORT Accession No.
Report No. _ EGG-EA-5891 e
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Contract Program or Project
Title:
Selected Opcrating Reactors Issues Program (III) 4 Subject of this Document:
Adequacy of Station Electric Distribution System Voltages, Big Rock Point Plant Type of Document:
Informal Report Author (s):
A. C. Udy Date of Document:
June 1982 Responsible NRC Individual and NRC Office or Division:
R. L. Prevatte, Division of Systems Integration This document was prepared primarily for preliminary or internal use. it has not received full review and approval. Since there may be substantive changes, this document should not be considered final.
EG&G Idaho, Inc.
Idaho Falls, Idaho 83415 r-Prepared for the U.S. Nuclear Regulatory Commission Washington, D.C.
J Under DOE Contract No. DE-AC07-761001570 NRC FIN No.
A6429 INTERIM REPORT
0207j e
ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES BIG ROCK POINT PLANT June 1982 A. C. Udy Reliability and Statistics Branch Engineering Analysis Division EG&G Idaho, Inc.
e a
Draft 6-01-82 TAC No.
ABSTRACT l
l This EG&G Idaho, Inc. report revicws the capacity and the capability of the onsite distribution system at the Big Rock Point Plant, in conjuntion with the offsite power sourtes, to automatically start and continuously operate all required safety loads.
FOREWORD l
This report is supplied as part of the Selected Operating Reactor Issues Program being conducted for the U.S. Nuclear Regulatory Comnission, 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 10 11, FIN No. A6429.
l E
ii
CONTENTS 1.0 I N TR O D U C T I O N....................................................
I 2.0 D E S I G N B AS I S CR I T ER I A...........................................
1 3.0 S Y S TE M D E S CR I PT I O N..............................................
2 e
4.0 AN A L YS I S D E S CR I P T I O N............................................
2 o
4.1 D e s i g n C h an g e s............................................
2 4.2 An a l ys i s C on d i t i o n s.......................................
2 4.3 Analysis Results..........................................
4 4.4 An al ys i s V er i f i c a t i on.....................................
4 5.0 E V A L U AT I O N......................................................
5 6.0 CO N C L U S I O NS.....................................................
6 7.0 REFERENCES......................................................
6 FIGURE 1.
Bi g Rock Point electrical s ingle-line di agram...................
3 TABLES 1.
Class lE Equipment Voltage Ratings and Anal yz ed Wor st Case Load Termi nal Vol tages......................
4 2.
Comparison of Analyzed Voltages and U n de rv ol t a ge Re l ay Se t po i n ts....................................
5 r
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1
)
ADEQUACY OF STATION ELECTRIC DISlRIBUTION SYSTEM VOLTAGES BIG ROCK POINT PLANT
1.0 INTRODUCTION
An event at the Arkansas Nuclear One station on September 16, 1978, i s 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 Aug st 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 IE loads.
Consumers Power Company (CPCo) responded with letters dated February 19, 1980,2 and August 29, 1980.3 CPCosuppljedfurtherinformation June 14,1978,ghisreviewonMargh 12,1980,gspondenceof requested for 23, 1981.
CPCo core August 21, 1980, and December were also reviewedfogthisreport. Additignalclarificationsweresubmittedon This information culminated in an EG&GIdaho,Inc., report.g1981.CPCo provided additional analysis, and May 4, 1981 and August 2 1982.j{iedtransformertapsettingchangesinasubmittaldatedMay18, ident Based on the information supplied by CPCo, this report addresses tne 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 within acceptable limits for required Class lE equipment, 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 Design Criterion 5 (GDC 5), " Sharing of Structures, Sys-tems, and Components," of Appendix A, " General Jesign Criteria for Nuclear Power Plants," of 10 CFR 50.
9 3.
General Design Criterion 13 (GDC 13), " Instrumentation and Con-
- rol," 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."
1
dated August 8,1979.} ailed in a letter sent to the licensee, Staff positions as de 5.
6.
ANSI C84.1-1977, " Voltage Ratings for Electric Power Systems and Equipment (60 Hz)."
jix review positions have been established from the NRC analysis guide-and the above-listed documents. These positions are stated in lines Section 5.0.
3.0 SYSTEM DESCRIPTION Figure 1 of this report is a simplified sketch of the unit single-line diagram of t It is taken from ge Big Rock Poigt power distribution system.
and Figure 1.
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.11, Load Center 1, and MCC-1 A can also supply MCC-28.
Both transformer No.11 and transformer No. 22 are energized by the same 2400V switchgear which is supplied via a voltage regulating transformer through transformer No.1 (from the unit generator or from the 138kV grid) or by the 46kV grid.
115V instrument and control panels are supplied from either MCC-1 A or MCC-28.
4.0 ANALYSIS DESCRIPTION 4.1 Des ign Changes.
CPCo has changed transformer taps as follows:
1.
Main transformer No. I tap is changed to the 140/13.5kV tap, and 2.
Transformer Nos.11 and 22 taps are changed to the 2340/480V tap.
No other design changes to the distribution system have been identified or proposed.
4.2 Analysis Conditions.
CPCo has determined by analysis and by historical data that the minimum expected offsite grid voltage is 131kV for the 138kV grid and 42kV for the 46kV grid, and that the maximum grid voltage is 142kV for the 138kV grid and 46kV for the 46kV 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 equipment terminal voltages occur under the following conditions:
s 1.
The minimum expected continuous load terminal voltage for a Class IE load occurs when the 138kV grid is at its minimum concurrent with a LOCA.
2
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i 2.
The minimum expected transient load terminal voltage for a Class lE load occurs when the 138kV grid is at its minimum concurrent with a LOCA and with the 100 hp fire pump starting.
3.
The maximum expected continuous load terminal voltage for a Class lE load occurs when the 138kV grid is at its maximum i-voltage, the voltage regulator is off-line, and the unit is in cold shutdown.
s 4.3 Analysis Result. Table 1 shows the projected worst case Class lE
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equipment terminal voltages.
t, TABLE 1.
CLASS lE EQUIPMENT VOLTAGE RATINGS AND ANALYZED WORST CASE TERMINAL VOLTAGES (% of nominal voltage) j Maximum Minimum l
Analyzed i
Equipment Condi tion Rated Analyzed Rated Steady State Transient I
80 86.8 440V Motors Start Operate 1 10 111.0a 90 98.3 ll5V Instru.
Operate 106.3b 101.8 90.lb 91.5 and i
Con trols 85 84.6c 480V Starters Pickup 65 84.6c Dropout Operate 125 101.8 85 91.4 a.
The analyzed voltage is the bus voltage and does not include the voltage drop in the motor feeder.
When this voltage drop is included, no Class lE motor will be subject to a voltage in excess of its rated voltage i
limit.
i l
b.
CPCo's most limiting instrument power supply, on a 480V base.
c.
During this starting transient, some 480V starters may not be able to pickup to operate additional loads. The loads will be energized as the voltage recovers above the starter pickup rating as the 100-hp fire pump motor starts. No loads will be dropped by this starting transient.
j 4.4 Analysis Verification. CPCo has verified the accuracy of the i
analysis for the Big Rock Point Plant by comparing voltages obtained by an oscillograph with analyzed voltages for the same condition (i.e., steady state and startup of the 100 hp fire pump on MCC-2B.) The test showed the analysis to be within the accuracy limits of the instrumentation used.
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1 5.0 EVALUATION lines}ix review positions have been established from the NRC analysis guide-and the documents listed in Section 2.0 of this report. Each r eview position is stated below followed by an evaluation of the licensee submi tt als.
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 starting and of continuously operating all Class 1E equipment within the equipment voltage ratings.
1 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).
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 relays will not cause the loss of the Class IE distribution system when the offsite grid voltage is within expected voltage limits.
Big Rock Point does not have a redundant Class lE distribution system.
TABLE 2.
COMPARISON OF ANALYZED VOLTAGES AND UNDERVOLTAGE RELAY SETPOINTS
(% of nominal voltage)
Minimum Analyzed
~- Relay Setpoint Location / Relays Voltage Time --
Vol tage _(ToTerance)
TideZ-~
2400V bus Degraded grid 96.3 continuous 90.1 (+0.9) 10.55s
(+0.55s)9 480V bus Loss of grid 84.6 5s less than or equal ins tan tan-o or less to 50 eous a.
Licensee has determined by analysis the minimum bus voltages with the of fsite grid at the minimum expected voltage and the worst case plant and Class lE loads.
5
Pos ition 4--The NRC letterl requires that test results verify the accuracy of the voltage analyses supplied.
CPCo has verified, by test, the validity of the anaysis for the Big Rock Point Plant.
Position 5--No event or condition should result in the simultaneous or consequential loss of both required circuits from the offsite power network to the onsite distribution system (GDC 17).
The Big Rock Point unit does not comply with GDC 17 since it has a k
single 2400V bus between redundent offsite grids to the single 480V Class 1E distribution system. The NRC will-examine this fully in the Systematic Evaluation Program, Topic VII-3, Safe Shutdown.
Position 6--As required by GDC 5, each of fsite source shared between units in a nulti-unit station must be capable of supplying adequate starting and operating voltage for all required Class lE loads with an accident in one unit and an orderly shutdown and cooldown in the remaining units.
This applies to multi-unit plants, it does not apply to Big Rock Point, a single-unit station.
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 IE equipment are supplied for all projected combinations of plant load and offsite power grid conditions.
2.
The test used to verify the analysis shows the analyses to be an accurate representation of the worst case conditions analyzed.
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 where a single failure can negate both sources. This will be examined as part of Topic VII-3 of the Systematic Evaluation Program.
4.
Loss of offsite power to Class lE buses, due to spurious operation of voltage protection relays, will not occur with the offsite grid voltage within its expected limits.
7.0 REFERENCES
1.
NRC letter, William Ganmill, to All Power Reactor Licensees (Except Hunboldt Bay), " Adequacy of Station Electric Distribution Systems Vol tage," August 8,1979.
6
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.
CPCo letter, David P. Hoffman, to Director, Nuclear Reactor Regula-tion, NRC, " Adequacy of Station Electric Distribution Systems Volt-ages," Augus t 29, 1980.
4.
CPCo letter, David P. Hoffman, to Director, Nuclear Reactor Regula-tion, NRC, " Adequacy of Station Electric Distribution Systems Volt-1 ages," March 23, 1981.
j 5.
CPCo letter, William S. Skibitsky, to Director, Nuclear Reactor Regulation, NRC, "On-site Emergency Power Sources," June 14, 1978.
6.
CPCo letter, David P. Hoffman, to Director, Nuclear Reactor Regula-tion, NRC, " Degraded Grid Voltage," August 21, 1980.
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 Grid Protection," August 26, 1981.
- 10. EG&G Idaho, Inc. Informal Report, " Adequacy of Station Electric Distribution System Voltages, Big Rock Point Plant, Docket No. 50-155, TAC No.12781," A. C. Udy, September 1981, EGG-EA-5433.
- 11. CPCo Letter, T. C. Bordine to D. M. Crutchfield, NRC, " Station Electric Distribution System Voltages," May 18, 1982.
l 9
i 3
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