ML19347F189
| ML19347F189 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 03/31/1981 |
| From: | Udy A EG&G IDAHO, INC., EG&G, INC. |
| To: | Shemanski P Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19347F179 | List: |
| References | |
| CON-FIN-A-6429 EGG-EA-5325, NUDOCS 8105150432 | |
| Download: ML19347F189 (12) | |
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ENCLOSURE 2 EGG-EA-5325
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ADEQUACY OF STATION ELECTRIC DISTRI3UTION SYSTEM VOLTAGES, DRESDEN STATION - UNIT 1. DOCKE" NO.
50-10. TAC NO. 12764 t
A. C. Udy U.S. Department of Energy Idaho Operations Office
- Idaho National Enginesring 1.aboratory
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This is an informal report intended for use as a preliminary or working document I
i Prepared for the U. S. Nuclear Regulatory Coctission Under DCE Contrac: No. DE-AC07-76D01570 FIN No. A6429 Q
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INTERIM REPORT Accession No.
Report No. ECC-EA-5325 Contract Program or Proket
Title:
Electrical, Instrumentation and Control System Support Subject of this Document:
Adequacy of Station Electric Distribution System voltages, Dresden Station -
Cait 1, Docket No. 50-10. TAC No. 12764 Type of Document:
Informal Report Author (s):
A. C. Udy Date of Document-March 1981 Responsible NRC Individual and NRC Office or Division:
Paul C. Shemanski, Division of Licensing This docurr.ent was prepared pnmanly for preliminary or internal use. it has not received full review and approval. Since there may be substantive changes.this document shculd not be considered final.
EG&G Idaho. Inc.
Idano Falls. Idaho 83415
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Prepared for the U.S Nuclear Pegulatory Commission Washington, D.C.
Under DOE Contract No. DE AC07 761001570 NRC FIN No. AMC INTERIM REPORT O
0197J ADEQUACY OF STATICN ELECTRIC DISTRI3UTION SYSTEM VOLTAGES D d DEN STATION - UNIT NO. 1 Docket No. 50-10 March 1981 A. C. Udy Reliability and Statistics Branch Engineering Analysis Division EG M Idaho, Inc.
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A3STRACT The Nuclear Regulatory Commission has required all licensees to analyze ene electric powsr systes at each nuclear station. This review is to deter-mine if cne 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 Tecnnical Evaluation Report (TER) reviews the submittals for the Dresden Station Unic 1.
A separate TER reviews the submittals for Units 2 and 3.
The offsite power sources, in conjunction with the onsite distribution system, have been shown to have sufficient capacity and capability to auto-34tically start, as well as continuously operate, all required safety rela-ced loads within the equipment rated voltage limits in the event of either an anticipated transient or an accident coadition.
FOREWORD This report is supplied as part of the selected Electrical, Instrumen-tation, and Control Systems (EICS) issues program being conducted for the U.S. Nuclear Regulscory Commission, Office of Nuclear Reactor Regulation, Division of Operating Reactors, by EG&G Idaho, Inc., Reliability and Sta-ristics Branch.
The U.S. Nuclear Regulatory Commission funded the work under the auth-orization entitled, " Electrical, Instrumentation, and Control System Sup-port," B&R 20 19 01 06, FIN A6429.
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1 CONTENTS
1.0 INTRODUCTION
1 2.0 DESIGN S ASIS CRITERIA.....
1 3.0 SYSTEM DESCRIPTION 2
4.0 ANALYSIS DESCRIPTION 2
4.1 De s i gn Chan gu s........................
2 4.2 Analysis Conditions 2
4 4.3 Analysis Results.
4.4 Analysis Verification 5
5 5.0 EVALUAIION
6.0 CONCLUSION
S............................
6
7.0 REFERENCES
7 FIGURE 1.
Dresden Station, Uni: One Line Diagram, Unit 1 3
IABLE 1.
Class 1E Equipment Voltage Rating: and Worst Case Load Terminal Voltages.
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i ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGE 3 DRESDEN STATION - UNIT NO. 1
1.0 INTRODUCTION
An event at the Arkansas Nuclear One station on September 16, 1978 is described in NRC II Information Notice No. 79-04.
As a result of this event, station conformance to General Design Criteria (CDC) 17 is being questioned at all nuclear power stations. The NRC, in the generic letter of Aurust 8,1979, "Adeq2acy of Station Electric Distribution Systems Volt-ages," I required each licenses to confirm, by analysis, the adequacy of the voltage supplied each class 1E load. The letter included 13 specific guidelines to be followed in determining if the voltage is adequate to start and continuously operate the class 1E loads.
Commonwealth Edison Company (Ceco) responded to the NRC letter 1, for the D:esden Station, Unit 1 with a letter of February 1,19802 (which iaciudad a report on this subject, written by Sargent & Lundy). The Final Safety Analysis Report (75AR), additional analyses submitted on June 30, 3
4 1980, telephone calls in September 1980, and a letter of September 14, 5
1976, complace the information reviewed for this report.
Based on the information supplied by CECO, this repert addresses the capacity and capability of the onsite distribution system of Unit 1 o f the Dresden Station, in conjunction with the offsite power system, to maintain the voltage for the required class IE equipment within acceptable limits for the worst-case starting and steady-state load conditions.
2.0 DESIGN BASIS CRITERIA The pcsitions applied in determining the acceptability of the offsite i
voltage conditions in supplying power to equipment are derived from the following:
1.
General Design Critation 17 (CDC 17), " Electrical Power Systems," of Appendix A, " General Design Criteria for Nuclear Power Plants," of 10 CTR 50.
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2.
General Design criterion 5 (GDC 5), " Sharing of Struc-tures, Systems, and Components," of Appendix A, " General Design Criteria for Nuclear Power Plants," of 10 CTR 50.
3.
General Design Criterion 13 (CDC 13), " Instrumentation and Coacrol," of Appendix A, " General Design Criteria for Nuclear Power Plants," of 10 CTR 50.
4.
IEEE Standard 308-1974, " Class 1E Power Systems for Nuclear Tower Generating Stations."
5.
Staff positions as detailed in a letter sent to the Licensee, dated August 8, 1979.1 1
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6.
ANSI C84.1-1977, " Voltage Ratings for Electric Power Systems and Equipment (50 Hz)."
Six review positions have been established from the NRC analysis guide-linesl and the above-listed documents. These positions are stated in Section 5.
3.0 SYSTEM DESCRIPTICN Tigure 1 of this report is a simplified sketch of the Unit i uni:
one-line diagram taken from the Sargent & Lundy report of reference 2 and Sargent & Lundy drawing #12-E-5.
This figure shows that the'elass 1E dis-tribution system is normally supplied power from 4160V auxiliary buses 11 and 12.
These auxiliary buses are supp?.ied power from the reserve auxiliary transformer (RAT) TR12, or unit auxiliary transformer (UAT) TR11. After a unit trip, TR12 continues to provide offsi:e power to the auxiliary and the.
class 1E distribution systems. Additionally, bus 11 (and, hence, II buses 112,113, and 117) can be supplied power from the 34.5kV grid via trans-former TR13; however, the CZco analysis does not show any 4160V loads ener-gized from this source.3 The unit generator can be isolated from the UAT to allow it to supply offsite power to the connected distribution buses as a reserve source. There are no power connections to Unit 2 or to Uni: 3.
Each of two 480V class 1E buses is supplied power from one of two class 1E 41507 buses via independent trans f ormers.
Ceco supplied the equipment operating ranges identified in Table 1.
Seation 125V DC buses supply power for 4150V class 1E switchgear.
4.0 ANALYSIS DESCRIPTICN 4.1 Design Changes _. Ceco has commi:ted to change the tap setting of transformer 12 to +2 '/ 2% voltage boost.2 The discussion in this report and the values in Table 1 are on the basis that this cap recting has been made.
4.2 Analysis conditions. Ceco has determined by load-flow studies that the max. mum 138kV switchyard voltage is 142kV and the minimum is 133kV.2 The 34.5kV swi:chyard voltage varies between 36.3kV and 34.8kV, respectively (contingency plans with the historical low voltage determined the lower vol: age).
Ceco has analyzed each offsi:e source to the onsi:e distribution system under extremes of load and offsite vol: age condi: ions to determine the terminal vol: ages to the class 1E squipment. The worst case class II equip-l 3ent"terzinsi voltages occur under the following conditions:
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The maximum expected load vol: age occurs with either
- ansformer 12 or 13 supplying power and when the i
switchyard voltage is maximum and there are no uni:
loads.
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CT. ASS 1E EQUIPMENT VOLTAGE RATINGS AND ANALYZED '4CRST CASE TERMINAI VOLTAGES
(% of nominal voltage)
Maximum Minimum Kated Analyzed Rated Analysed Nominal voltage Steady Equipment (1001) state Transient Motors 4kV Start 75 88.88 operate 110 109.7 90 96.lb 460V 5:ar 75 83.8a Operate 110 110.1 90 91.65 Starters 480V Fickup 85 81.3 Dro pout 70 81.3 operate 110 105.5 85 88.7 Other EquiptentC a.
Load terminal voltage supplied by CECO.
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These values include the addi: ion of the worst case (4807) or typical 2
(4160V) feeder :able voltage drop (1.0%, 0.5%, respectively ),
3 120V vi:a1 buses are normally supplied power by socor generator sets.
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These are sched' sled to be replaced by invertars. Self-regulating trans-formers provide an alternate source should the motor-generator set or inverter be out of service.4 2.
The minimum expected continuous load vol: age occurs wi:h transformer 12 supplying power, the 138kV svi:ch-yard vol: age is minimum, and all buses are fully loaded (except for loads shed due to unit trip).
3.
The minimum expected transient load vol: age occurs under the condi: ions of 2, concurrent with the start of a large load.
4.3 Analysis Results. Table i shows the worst case voltage levels iden:ified in :na Ceco analyses.
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4.4 Analysis verification. Ceco has not committed to verify the accuracy of tasir voltage analysis. One acceptable method would be to measure the grid voltage, the class 1E bus voltages, and the actual class 1E bus load, and then compara these measured values with an analysis that uses the seasured offsite source voltage and the measured bus loads. CICo mus establish that the load conditions and instrument accuracies used in the test are adequate to account for impedance and transformer voltage drops in the distribution s/ stem.
5.0 EVALUATION Six review positions have been established from the NRC analysis guide-linesl and the documents listed in Section 2.
Each review position is stated below, followed by the evaluat.on of the licensee submittals.
i Position 1-With the ministne expected offsite grid voltage and maximum load condition, each offsite source and distribution system connectico combination must be capable of starting and of continuously operating all class 1Z equipment eithin the rated equipment voltages.
A brief acceptable condition, when starting the largest socor on 4160V bus 11 or 12, would prevent class 1Z contactor pickup, if a 480V MCC load were stopped and then restarted, until the voltage recovers. It will not cause contactor dropout or spurious shedding of any loads.
CICo has shown by analysis that Dresden 1 has sufficient capability and capacity for starting and continuously operating the class II loads within the equipment voltage racings (Table 1).
Position 2-With the maximum expected offsite grid voltage and minimum lead condition, each offsite source and distribution system connection combination must be capable of continuously operating all class 15 equip-sent without exceeding the rated equipment voltage.
As can be seen from Table 1, all loads are opera'ted within 411ovaote voltage limits, except for the potential 110.1% on the 480V buses. Ceco concluded that the safety loads at Dresden Uni I would not be subjected to unacceptable overvoltage because this analysis was done for a no-load condition which does not exist when the equipten't is powered; that voltage drops in the supply transformers and feeder cables would reduce the 110.1%
to within an acceptable voltage range.
CECO has shavn that by analysis that the voltage racings of the class II equipment will not be exceeded.
. Position 3--Loss of offsite power to either the redundant class 1E distribution systtaa or the individual class LZ loads, due to operation of voltage protsecios relays, sust not occur when the offsite power source is within analyzed voltage 1Laits.
EG&G Idaho, Inc., will verify, in a separate report, that this position is satisfied (IAC '.a. 10020).
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l Position 4--Test results should verify the accuracy of the voltage analyses supplied.
Ceco has not committed to verify the accuracy of the voltage analyses for Dresden, Unit 1.
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).
Ceco has analyzed the connections of the Dresden Station to the off-site power grid, and has determined that no potential exists for the simul-taneous or consequential loss of both circuits from the offsite grid.
a shared between Position 6--Aa required by GDC 5, each offsite source units 4.n a multi-unit station sust be capable of supplying adequate starting and operating voltage for all required class 1E loads with an accident in one unit and an orderly shutdown and cooldown in the remaining units.
Dresden Unit 1 is connected to offsite power independently of Dresden Unit 2 and Unit 3.
No common electrical connections exist; therefore, this position does not apply.
6.0 CONCLUSION
S The analyses submitted by Ceco for this review were evaluated as stated in Section 5 of this report. These submittals show that, af ter the trans-former #12 cap settings are chaeged to 21/2% boose:
1.
Voltages within the operating limits of the class 11 equipmeet are supplied for all projected combinations of plant load and offsite power grid voltage conditions.
2.
CECO has determined that no potential for either a simultanous or consequential loss of both offsite power sources exists.
3.
CECO has act committed to show, by test, that their analysis of the Dresden Station distribution system is an accurate representation of the actual voltages. One acceptable method is outlined in Section 4.4 of this report.
CICo should be required to perform tests to verify the accuracy of their analysis, s.
Section 8.1.1 of IEEE Standard 308 permits the use of a single source of offsite power to be shared between units of a multi-unit station.
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EG&G Idaho, Inc., is providing a separate review of the undervoltage relay protection at Dresden 1.
This will evaluate the relay setpoints and time delays to determine that spurious tripping of the class 1E buses will not occur with normal offsite source voltages.
7.0 REFERENCES
1.
NRC letter, William Gammill, to All Power Reactor Licensees (Except Humboldt 34y), Adequacy of Station Electric Distribution Systems voltages," August 8, 1979.
2.
Ceco letter, Robert 7. Janecek to William Cammill, "Adequancy of Sea-tion Electric Distribution Syseen Voltages", February 1,1979.
3.
CECO letter, Robert T. Janecek, to T. A. Ippolito, U. S. NRC, " Adequacy of Station Electric Distribution System voltages," June 30, 1980.
4.
Telecon, E41 Scott, Ceco and other Ceco personnel and Alan Udy, EG6G Idaho, Inc., September 11, 22, and 25,1980.
5.
Ceco letter, G. A. Abre11, to Karl 1. Coller, U.S. NRC, "Information Concerning System Voltage Conditions," September 14, 1976.
6.
CECO letter, Robert F. Janecek, to Darrell G. Eisenhut, U.S. NRC, "Second Level of Undervoltage Protection for 4kV Onsite Emergency Power Systems," June 26, 1980.
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