ML20050B282
| ML20050B282 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 02/01/1982 |
| From: | Selan J LAWRENCE LIVERMORE NATIONAL LABORATORY |
| To: | |
| Shared Package | |
| ML20050B275 | List: |
| References | |
| UCID-19124, NUDOCS 8204050166 | |
| Download: ML20050B282 (11) | |
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UCID. 19124 TECHNICAL EVALUATION OF THE ADEQUACY OF
- >TATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES f
FOR'THE HADDAM NECK NUCLEAR POWER PLANT l
James C. Selan SELECTED ISSUES PROGRAM (Docket No. 50-211)
February 1, 1982 1
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DISCLAIMER This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warrsnty. expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information apparatus, product, or process disclosed. c' represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufac-turer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof.The <iews and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
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Avsilable from: Sstional Technical Information Service - U.S. Department of Commerce 5:35 Port Royal Road SpnngGeld. V A 22161 -
55.00 per copy - (Micronche 53.50s
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ABSTRACT This report documents the technical evaluation of the adequacy i
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of the station electric distribution system voltages for the Haddam Neck The evaluation is to determine if the onsite distri-Nuclear Power Plant.
bution system', in conjunction with the offsite power sources, has sufficient and operate all Class lE loads within the capacity to automatically start equipment voltage ratings under certain. conditions established by the Nuclear Regulatory Commission.
the electric distribution system has the The analysis shows that capacity and capability to supply adequate voltage to the Class lE equipment, provided that the grid is maintained at or above the administrative minimum limits.
FOREWORD This report, is supplied as part of the Selected Electrical, Instrumentation, and Control Systems Issues (SEICSI) Program being con-ducted for the U. S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation, Division of Operating Reactors, by Lawrence Livermore 1
National Laboratory.
The U. S. Nuclear Regulatory Commission funded the work under the authorization entitled " Electrical, Instrumentation and Control System Support,"
&&R 20 19 04 031, FIN A-0250.
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TABLE OF CONTF.NTS Page 1
1.
INTRODUCTION.
2 2.
DESIGN BASIS CRITERIA 2
- 3.. SYSTEM DESCRIPTION i
4 4.
ANALYSIS.
4 4.1 Analysis Conditions.
4 4.2 Analysis Results.
4 4.2.1 Overvoltage.
4 4.2.2 Undervoltage.
6 4.3 Analysis Verification 6
5.
EVALUATION 7
6.
CONCLUSIONS 8
REFERENCES ILLUSTRATIONS FIGURE 1 Haddam Neck Nuclear "ower Plant 3
Electrical One-Line Diagram.
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TABLE 1 Haddam Neck Nuclear Power Plant Class lE Equipment Voltage Ratings and Analyzed 5
Worst Case Terminal Voltages.
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TECHNICAL EVALUATION OF THE ADEQUACT OF STATION ELECTRIC DISTRIBUT20N SYSTEM VOLTACES FOR THE HADDAM NECK NUCLEAR P0t.*ER PLANT (Docket No. 50-213)
James C. Selan 1
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INTRODUCTION
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The Nuclear' Regulatory Commission (NRC) by a letter dated August 8, 1979 (Ref. 1], expanded its generic review of the adequacy of the station electric distribution systems for all opercting nuclear power facilities.
This review is to determine 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.
In addition, the NRC requested each licensee to follow suggested guidelines and to meet certain requirements ia the review. These requirements are detailed in Section 5 of this re po rt.
By letters dated November 15, 1979 [Ref. 2], March 6, 1980 (Ref. 3],
August 21, 1980 (Ref. 4], November 4, 1980 (Ref. 5], October 23, 1981 (Ref. 6], and December 10, 1981 (Ref. 7].
Connecticut Yankee Atocic Power Co' pany (CYAPCO), the ficaniee~, ~sulimitted their analysis and conclusion m
regarding the adequacy of the electrical distribution system's voltages at Haddam Neck Nuclear Power Plant.
The purpose of this report is to evaluate the licensee's submittal with respect to the NRC criteria and present the reviewer's conclusion on the adequacy of the station electric distribution systems to maintain the voltage within the desig'n limits of the ' required Class lE equipment for the worst case s' tarting and load conditions.
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2.
DESIGN BASIS CRITERIA The design basis criteria that were applied in determining the adequacy of station electric distribution system voltages to start and operate all required safety loads within their required voltage ratings
, are as follows:
(1) General Design Criterion 17 (GDC 17), " Electric Power Systems," of Appendix A, " General Design Criteria for-Nuclear Power Plants," in the Code of Federal Regulations, Title 10, Part 50 (10 CFR 50) (Ref.,8].
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(2) General Design Cr1terion 13 (GDC 13), " Instrumentation and Control," of Appendix A. " General Design Criteria for Nuclear Power Plants," in the Code of Federal Regulations, Title 10, Part 50 (10 CFR 50) (Ref. 8].
(3) ANSI C84.1-1977, " Voltage Ratings for Electric Power Systems and Equipment" [Ref. 9].
(4) IEEE Std 308-1974, " Class lE Power Systems for Nuclear Power Generating Stations" [Ref. 10].
(5) " Guidelines for voltage Drop Calculations," Enclosure 2, to NRC letter dated August 8, 1979 [Ref. 1].
3.
SYSTEM DESCRIPTION A one-line diagram of the plant's electrical distribution system is shown in Figure 1.
The electrical distribution system is designed so that during plant startup conditions, the total station service demand is supplied by the 115 kV system through service station transformers 389 and 399.
Af ter the plant has attained operating conditions, 4160-volt buses 1-13 and 1-1A are transferred to service station transformer 309. Should the supply through service station transformer 309 fail, buses 1-1A and 1-1B are automatically transferred to the 115 kV supply (transformers 389 and 399).
With the loss of a normal 115 kV supply to buses 1-2 or 1-3, the loads will automatically be transferred to the remaining bus section by closing tie breaker 2T3 (normally open). Upon restoration of the 115 kV supply, an automatic retransfer will return the lead groups to their normal supply and open tie-breaker 2T3.
Tie-breakers between 480-volt bus sections permit manual transfer to adjacent buses, but interlocks prevent concurrent closure with the supply breakers to prevent circulating currents. Tie-breaker ST6 is permanently removed from its cubicle to prevent paralleling of the redundant load groups. t t
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ANALYSIS 4.1 ANALYSIS CONDITIONS CAYPCO has analyzed each offsite source to the onsite distrib'ution system under minimum and maximum load demand conditions and offsite voltages.
to determine the voltages at.the terminals of the Class 1E equipment. c.The-;
minimum offsite grid voltage used was 106 kV..The 106 kV value is below
'the grid' administrative limit of 106.4 kV when both service station trans-formers 389 and 399 are in service. When only one'of the two service station transformers is in service, an administrative limit of 110.8 kV is used. The maximum expected grid voltage used in the analyses is 117 kV.
However, present
. operating limits specify an upper. limit of 114.7 kV.
Calculated typical voltage drops of 10 volts for 480-vole running loads, 50 volts for 480-volt starting loads, 20 volts for 4160-volt running loads, and 100 volts for 4160-volt starting loads were used in the analyses.
Both charging pumps, all service water pumps, and all CAR fans are considered in operation for normal full load case studies.
When starting these individual loads, the running load of the motor is still considered to be part of the normal full load, thus making the analysis more conservative. The effect on the Class 1E equipment when starting a large non-Class lE load after the Class lE buses are fully loaded was also analyzed.
4.2 ANALYSIS RESULTS The worst case Class lE equipment terminal voltages occur under the following conditions:
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4.2.1 Overvoltage Minimum station load with a maximum grid voltage of 117 kV, unit-in shutdown mode, and either 1 or 2 station service transformers in service.
4.2.2 Undervoltage F1:nt trip with LOCA, minimum grid voltage of 106 kV, two station service transformers in service, normal full loads', accident loads starting and running.
These worst case Class lE equipment terminal voltages are shown in Table 1.
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TABLE 1 4
i FJWDAM NECK NUCLEAR POWER PLAN CLASS lE EQUIPMENT VOLTAGE RATINGS AND ANALYZED WORST CASE TERME!AL VOLTACES (in : of Equipment Nominal Voltage Rating)
Maximum tiinimum
' Rated Analyzed (a) Rated Analyzed (a)
Nominal Voltage Racing Steady Steady Equipment (100 %)
State State Transient (b)
Motors 4000 start 80 87.9 Operate 110.0 110.1 90 95.8 440 start 80 80.9 Operate 110.0 112.0 90 96.1 Starters 440 Pickup 87.7 96.1 Dropout 48.6 80.9 Operation 110.0 112.0 90 96.1 Other Equipment (c)
Footnotes:
(a) CTAPCO does not consider backfeeding through main transformer 319 and service station transformer 309 a viable source connection; therefore no analysis was submitted. Bus loading is considered to be conservative because while starting individual loads (i.e. charging and service water l
pumps and the CAR fans), the running load for these starting motors are i
not removed from the loading condition on the buses.
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(b) These voltages represent the lowest transient voltage reached at the terminals of the Class 1E equipment during load starting.
(c) All " vital low voltage AC" is supplied from inverters and all " semi-vital low voltage AC" is supplied by regulating transformer with the exception of the service water filter motors which are not considered Class lE.
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u 4.3 ANALYSIS VERIFICATION.
1 CYAPCO verified their gomputerized. voltage analyses calculations by measuring the loads and voic4ges on each cf the buses and the offsite
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supply voltage.
Using the measured loads and offsite source voltage, bus
- voltages were calculated using the cciputerized transformer voltage drop method. The measured voltages were then compared to the calculated, voltages r
producing error differences of -0.86 to_-2.56 percent for steady state condi-l*
tions on the 4160-volt and 4,80-volt buses respectively.
The plant was at full load with bus loading from 29% to 91".
A minus percentage error indicates the measured values to.be higher than the calculated values.
5.
EVALUATION i
The NRC generic letter (Ref. 1] stated several requirements that the plant voltage analysis must meet. These requirements and an evaluation of the licensee's submittals are as follows:
(1) With the minimum expected grid voltage and maximum load condition, each offsite source and distribution system connection must be capable of starting and continuously operating all Class lE equipment within the equipment's voltage ratings.
The voltage analysis submitted by CYAPCO shows that the offsite sources, in conjunction with the onsite distribution system, have the capability and capacity to automatically start and continue to operate all Class lE equipment within their design ratings at the grid voltages of 106 kV (two service transformers in service) and 110.6 kV (one service station transformer in service).
l (2) With the maximum expected offsite grid voltage and minimum load condition, each offsite source and distribution system connection must be capable of continuously operating the required Class lE equipment without exceeding the equipment's l
voltage ratings.
The analysis shows that for the conditions detailed in Section 4.2.1 the voltage at the terminals of the Class lE equipment could exceed the design ratings by 2% at the 480-volt level.
The licensee has proposed to install overvoltage monitors on the 4160-volt and 480-volt Class lE buses. The relays will be Class lE, and will alarm through non-Class 1E annunciators.
The relays' setpoints are 492 volts at the 480-volt buses and 4410 volts at the 4160-volt buses. t 1
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(3) Th'a analysis =ust show that there will be no spurious sepa-ration from the offsite power. source to the Class lE buses by the voltage protection relays when the grid is within the normal expected limits and that the loading conditions established by the NRC are being met.
LLNL will verify in a separate report (TAC No. 10025) that the requirements of this position are met.
(4) Test results are required to verify the voltage analyses calculations submitted.
CYAPCO verified the voltage analysis by test. The error differences between measured values and the calculated values confirm that the analysis results are acceptable.
(5) Review the planr's electrical power systems to determine if any events or conditions could result in the simultaneous loes of both offsite circuits to the onsite distribution system (compliance with CDC 17).
CYAPCO reviewed the electrical power system and identified two events which could result in the simultaneous loss of both required circuits. These events are the failure of 4160-volt tie breaker 2T3 and the failure of 115 kV breaker 389T399 (Fig. 1).
The failure of 2T3 will automatically
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clear 4160-volt buses 1-2 and 1-3 to isolate the fault.
The failure of 389T399 will automatically. trip the two 115 kV lines (1772 and 1206).
6.
CONCLUSIONS Based on the information submitted by CYAPCO which is evaluated in l
Section 5 of this report, it is concluded that:
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l (1) By installing the proposed Class LE overvoltage monitors which~
l will alarm through non-Class lE annunciators, corrective action can be taken to eliminate overvoltages at the terminals of the Class lE equipment.
(2) A separate review of the undervoltage protection scheme will be made to determine that spurious tripping from the offsite sources t
will not occur for the' loading conditions analyzed.
(3) The test verification results verify the accuracy of the voltage analysis submitted.
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j (4) The Class 15 equipment will be operating within the voltage design li=its for the worst case loading conditions with the grid voltage at 106 kV for two service station transformer operation and at the administrative limit of 110.6 kV for one service station transformer operation.
(5) Additional studies should be made on the two single events which could result in loss of both offsite sources, that are detailed in Section 5. Item 5.-
The additional studies will be made by the systematic evaluation program (SEP) under topic-7.3, entitled
" Systems Required-for Safe-Shutdown". ;__
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I recommend that NRC approve the voltage' analysis submitted which shows that the station electric distribution system is adequate to supply acceptable voltages for the worst case loading conditions.
REFERENCES 1.
NRC letter (W. Gammill) to all Power Reactor Licensees, dated August 8, 1979.
2.
Northeast Utilities letter (W. G. Counsil) to NRC (D. L. Ziemann),
dated November 15, 1979 3.
CYAPCO letter (W. G. Counsil) to NRC (D. L. Ziemann),
dated March 6, 1980.
4.
CYAPCO letter (S. G. Counsil) to NRC (D. M. Crutchfield),
dated August 21, 1980. -
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CYAPCO letter (W. G. Counsil) to NRC (D. M. Crutchfield),
dated November 4, 1980.
6.
CYAPCO letter (W. G. Counsil) to NRC (D. M. Crutchfield),
dated October 23, 1981.
7.
CYAPCO letter (W. G. Counsil) to NRC (D. M. Crutchfield),
dated Dece=ber 10, 1981.
8.
Code of Federal Regulations, Title 10, par: 50 (10CFR50),
General Design Criterion 13 and 17 of Appendix A for Nuclear Power Plants.
9.
ANSI CS4.1-1977," Voltage Ratings for Electric Power Systems and Equipment".
10.
IEEE Std. 308-1974, " Class lE Power Systems for Nuclear Power Generating Stations".
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