ML20008F281

Safety Evaluation of EGG-EA-5252, Adequacy of Station Electric Distribution Sys Voltages,Trojan Nuclear Power Station

ML20008F281
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Site:	Trojan File:Portland General Electric icon.png
Issue date:	02/24/1981
From:	Office of Nuclear Reactor Regulation
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References
TAC-48370, NUDOCS 8103120731
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Text

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February 24, 1981

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SAFETY EVALUATION TROJAN NUCLEAR PLANT DOCXET NO. 50-344 ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES INTRODUCTION AND

SUMMARY

Portland General Electric Company (PGE) was requested by NRC letter dated August 8,1979 to review the electric power system at Trojan Nuclear Plant.

The review was to consist of:

(a) Determining analytically tne capacity and capability of the offsite power system and the onsite distribution system to automatically start as well as operate all required loads within neir required voltage ratings in the event of (1) an anticipated transient, or (2) an accident (such as LOCA) without manual shedding of any electric loads.

(b) Determining if there are any events or conditions which could result in the simultaneous or consequential loss of both required circuits from the offsite network to the onsite electric distribution system and thus violating the requirements of GDC 17.

The August 8,1979 letter included staff guidelines for performing the required voltage analysis and the licensee was further required to perform a test in order to verify the validity of the analytical results.

PGE responded by' letters dated October 5,1980, January 11,1980, Feoruary 25, 1980 and June 30, 1980. A detailed review and tecnnical evaluation of the subrittal was performed by EG&G under contract to NRC, and with general B10812 0%

. supervision by NRC staff. This work was reported in EG&G's Technical Evaluation Report (TER)," Adequacy of Station Electric Distribution Systems Voltages, Trojan Nuclear Power Station" dated September 1980. We have reviewed this report and concur in the conclusions that the offsite power system and onsite distribution system are capable of providing acceptable voltages at the terminals of the Class lE equipment' for worst case station electric load and grid voltages.

EVALUATION CRITERIA The criteria used by EG&G in this technical evaluation of the analysis includes GDC 5 (" Sharing of Structures, Systems, and Components"), GDC 13

(" Instrumentation and Control"), and GDC 17 (" Electric Power Systems") of Appendix A to 10 CFR 50; IEEE Standard 308-1974 (" Class lE Power Systems for Nuclear Power Generating Stations"); ANSI C84.1-1977 (" Voltage Ratings for Electric Power Systems and Equipment - 50 Hz"); and the staff positions and guidelines in NRC letter to PGE dated August 8,1979.

l ANALYSIS AND TEST FEATURES Various analyses were performed using the unit auxiliary and start-up trans-formers with maximum and minimum switchyard (grid) voltage (240 kv and II: <v respectively).

It has been estaclished that na emergency a kv loads scuit operate within allowable limits for the worst cases noted a ove. Given the minimum voltage case, a brief conaition exists while starting a large non-lE motor with the unit buses fully loaded that would prevent momentarily contactor pickup for 480 volt MCC loads until the voltage recovers. No c:r. ac or drop cut or s;uricus snedding of lead wili :c:ur.

This momentary i

. inability to start 480 volt loads is not significant due to the very short time of concern and the fact that it only becomes a concern if concurrently:

the grid is at its lowest allowable level and there becomes a need to auto-matically start an emergency load during the initial phase of the starting transient of a large non-Class lE load.

The voltage analysis was verified by measuring voltages and loacs at various lE and non-l E buses while the unit was operating at 1005 capacity.

The comparison showed that calculated voltages for the Class lE buses are within

0.58% of the measured voltages. This close correlation verifies the accuracy of the analysis submitted.

CONCLUSIONS We have reviewed the EG&G Technical Evaluation Report and concur in the findings that:

(1 )

PGE has provided verified voltage analyses to demonstrate that the Class IE equipment voltages remain within acceptable operating l

limits for the postulated worst case conditions.

(2) The tests performed demonstrated the validity of the mathematically analyzed values of the Class lE equipment terminal voltages.

l (3) PGE's reaffirmation of compliance with GDC 17 requirements is acceptabl e.

(4) Upon the review and approval of the degraded grid voltage protection modifications currently being evaluated by EG&G, there will be accept-l l

able assurance that spurious td::"g of offsi e :cwer to Class lE ecuioment will not take :iace.c:e itarting a lar;e ncn-Class lE loac.

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l ECO-EA-5252 Septe=ber :.980 ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM i

l VOLTAGES, TROJAN NUCLEAR P0hT.R STATION, DOCKET NO.

50-344 TAC No. 12957 I

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U.S. Department of Energy I

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Adequacy of Station Electric Distribucion System Voltages, Trojan Nuclear Power station, ':ocke: No. 50-344. TAC No. 12957 Type of Document:

nformal Repor:

Author (s):

A. C. Udy Date of Document:

September 1980 Responsible NRC Individual and NRC Office or Division:

Paul C. Shenanski, DivisJon of Licensing This cocument was preparec pnmanly for preliminary orinternal use. It nas not receivec full review anc accrovat Since there may be suestantive enanges. this document snoula l

not ce consicerec final.

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U.S. Nuclear Regulatory Commission Wasnington. O.C.

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1719F TECHNICAL EVALUATION REPORT ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES TROJAN NUCLEAR P0fdER STATION Docket No. 50-344 Septemoer 1980 A. C. Udy Reliability and Staciacies Branch Engineering Analysis Division EG(nG Idalto, Inc.

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ABSTRACT The Nuclear Regulatory Commission has required all licensees to analy e ene electric power system at each nuclear station. This review is to deter-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 Trojan Nuclear Power Station.

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 either an 2nticipated transient or an accident condition.

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FORE'40RD

!his repor: is supplied as par: of :he selec:ed Electrical, las:ru-mentation, and Con:rol Systems (EICS) issues program being condue:ed f ar

na 'J.S. Nuclear Regulatory Commission, Office of Nuclear Reac:or Regula-tion. Division of Operacing Reactors, by EG&G Idaho, Inc., Reliasili:y and S:4:is:ics 3:anch.

!ae U.S. Nuclear Regulatory Commission funded the work under :he su:h-ari:stion anci: led " Electrical, Ins:rumentation, and Con::al Sys:em Sup-port," 3&R 20 19 01 03, F:N No. A6256.

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CONTENTS 1.0 IKIRODUCTION 1

2.0 DESIGN 3 ASIS CRITERIA.

L 3.0 SYSTEM DESCRIPTION 2

.0 ANALYS'IS DESCRIPTION a

4.1 Analysis Conditions a

4.2 Analysis Results 6

1.3 Analysis-Verification 6

3.0 EVALUATION 7

6.0 CONCLUSICMS.

3

7.0 REFERENCES

9 FICURE 1.

Trojan unit single-line diagram.

3 TABLE 1.

Trojan Nuclear Power Station Class IE Equipment Voltage Ratings and I

Worst Case Available Load Terminal Voltages 5

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TECHNICAL EVALUATION REPORT ADEQUACY OF STATION ELECTRIC DISTRI3UTION SYSTEM VOLTAGES TROJAN NUC W R POWER STATION 1.0 INTRODUCTICN An even: 4: the Arkansas Nuclear One station on September 16. 1973 is described in NRC IE Information Notice No. 79-0a. As a result of :his event, s:a: ion conformance :o General Design Cri:eria (CDC) 17 is being questioned 4: all nuclear power stations. The NRC, in :he generic let:er of Augus: 3,1979, " Adequacy of Station Elec:ric Dis:ribution Sys: ems Vol:-

ages," I required each licensee to confirm, by analysis, :he adequacy af

ae vol: age a: :ne : Lass 1E loads. This le::er included 13 specifi guide-lines :o be followed in de:ermining if :he load :erminal vol: age is adequa:e

o star: and continuously operate the class lE loads.

Por: land General Electric Company (PCE) supplied an analysis for :his review in a le::er of October 5,1979'.

Informa ion supplied on 3

January 11, 1980, suosequen: additional analysis suomi::ed for :his review on February 25, 1980 and on June 30, 1980, and telephone con-5 versa: ions in September 1980 complete the information reviewed for :his report.

3ased on :he informa: ion supplied by PGE, :nis repor: addresses the capaci:y and capability of :he onsite distribution system of the Trojan Nuclear Power Station, in conjune: ion wi:h :he offsi:e power system, :s main:ain :he voltage for :he required class 1E equipment wi:hin accep -

able limi:s for :he worst-case starting and load condi: ions.

2.0 3ESIGN 3 ASIS CRITERIA i

The posi: ions spplied in de:ermining :he ac:eptability of :he off si:e voltage condi: ions in supplying power to :he : lass II equipment are derived from :he following:

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General Design Criterion 17 (GDC 17), "Elec: ical 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 struc-tures, Systans, and Components," of Appendix A, " General Design Criteria for Nuclear Power Plants," of 10 CFR 50 3.

General Design Criterion 13 (GDC 13), "Instrumenta: ion and Control," of Appendix A, " General Dasign Criteria for Nuclear Power Plants," of 10 CFR 50 4.

IEEE Standard 308-1974, " Class 1E Power Systems for Nuclear Power Generating Stations" 5.

Staff positions as detailed in a letter sent to the 1

licensee, dated August 3, 1979 s.

INSI C84.1-1977, " Voltage Racings for Electric Power Systems and Equipment (60 Hz)."

Six review posi: ions have been established from the NRC analysis guide-lines and tha above-listed documents. These positions are stated in Section 5.

3.0 SYSTEM DESCRIPTION Section 3.1.2 of the Trojan Final Safety Analysis Report (FSAR) and Par: II of Reference 2 discuss the onsite distribution system. Figure 1 of this report is a simplified sketch of the unit single-line diagram taken from Figure 3.3-1 of the ~SAR.

Normal Operation of the unit has the main generator supplying power :o all plant loads (class IE and non-class JE) through the unit auxiliary

ansformer (UAT)1 The plant loads remain powered by :he uni: generator for c.te duration of the 30-second time delay af:er a reactor trip, before s uni: : rip occurs.

C* ass IE loads required by any design basis accident (DBA) would be sequenced onto the UAT during :his 30-second period.

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s Foliowing a uni: : rip, :he ;ian: auxiliary load" has.s f as t transfer irac :ne UAr to :he two scartup ::ansformers (SUT)*.

The power to :he DBA equipment is dropped, and is again sequentially loaded. Upon failure of an SUT, use of :ne uni: generator disconnect link allows :he main uni:

ransformer and the UAT to supply offsite power to the auxiliary and class IE loads. This is not specifically prohibi:ed by Technicat S pec ifica: ions.

Eacn SUT aormally supplies, as tne preferred source, power for one redundan: Jafe:y train and one-half of the plan: auxiliary loads. However, as :an ce seen in Figure 1, an inter:ie between 4160V buses A5 and A6 exis:s. However, Technical Specification limicing condi: ions of operation

'. imi: :ne use of :nis inter:ie. Trojan periodi: operating :est POT-21-2 verifies tha: inter:ies are not used.

PGE supplied :he equipment operating ranges identified in Table L.

4.0 ' ANALYSIS DESCRIPTION l

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4.1 Analysis Condi: ions. PGE has provided analyses for various con-i ditions.*'5 The analysis for each condition was for the buses aligned :o

he normal sour:e of power wi:hout use of bus intercies. Since :he Techni-cal Specification 3.3.2.1, prohibits use of the inter:Les between redundant muses during operation, the use of :he inter ies between the class 1E buses sere not analy:ed.

A Among :ne condi: ions ?CE used for their analysis are :he following:

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1.

The scar:2p ::ansformer :ap will be :he nominal :ap for l

opera: tag condi: ions, the +2.5"

ap for shu:down condi-s l

ions, acwever, PGE supplied analyses for :he nominal

ap for 'ooth the operating and :he shu:down modes 2.

The uni: auxiliary transformer :ap will be :he nominal cap for operating condi: ions s.

Auxiliary loacs, as used in :his repor:, refers to non-class 15 loads.

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TABLE 1 IROJAN NUCLEAR POWER STATION CLASS LE EQUIPMENT VOLIAGE RATINGS AND WORST CASE AVAILtBLE LOAD TERMINAL VOLTACES (in : of equipment nominal voltage rating)

Maximus Minimum Minimum Steady State Steady State Transient Equipment Nominal Voltage Rating Rated Analyzed Rated Analyzed Rated Analy:ed' 0007 motor 110 109.5 90

' 96.2 70 35.4 4o0V motor 110 108.7 90 90.2 70 77.6 180V motor contactors b

87.5 89.4 37.5 74.4 pickup c

55 39.4 55 74.;

dropout

• c less enan 487/I The analyzed voltages are the extremes of the analyses provided by PCE, a.

using boca che start-up and th'e unit auxiliary transformers as sole sources, b.

These analyzed voltages for the motor contactors are at the 430V bus.

The maximum voltage the 480V contactors can withstand was not provided c.

oy PCE.

d.

No analysis was provided for 120V AC instrumentation, as these are supplied power from inverters whose regulated output is independent of the cener class 1E AC buses.

i 3.

A load survey determined snatdown load requirements L.

The reactor coolant pumps and heater drain pumps are l

considered as not tripped after the plant trip l

3.

The normal plant auxiliary considers the following

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equipment as not operating:

a.

Fire pump l

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Control rod drive motors (not operating af ter a plant trip) c.

Containment spray pump d.

Charging pump 5

a.

Safety injec: ion pump f.

Residual heat removal pump g.

Room fans for the above pumps 5.

Analyses for both tne unit auxiliary transformers and the start-up transformers were provided by PGE 7.

For the worst-case transient voltage degradation, PGE analyzed for the start of a circulating water pump when all :he safety loads were operating, a.2 Analysis Resulta. PGE has provided analyses as required by :he NRC lat:er. '4hile a grid voltage of 235kV was identified as the histor-ical low, 230kV was used for :he analysis since the second level of under-vol: age protection relays operate at : sis level.' The historical hign grid vol: age, 240kV, was used for ths maximum vol: age analysis.

Taole 1,shows the worst case voltage levels identified from :he ?GE analyses. The analyses show. chat all class 1E loads are capable of starting and continuously operating over a grid vol: age range : hat is wider :han :he historical grid voltage range at the Trojan station.

A brief condition wnile starting a circulating water pump when the uni: buses already fully loaded will prevent contactor pickup for the a80V MCC loads until the voltage recovers. It will not cause contactor dropout se spurious snedding of any loads.

A.3 Analysia Verification. PCE verified the computer analysis.

This was done by measuring the unit generator voltage and by raking vol:-

age, current, and power fac:or seasurements on auxiliary buses 31 and A3.

class lE buses A1, 301, and 303, class 1E MCO buses 321, 323, and 325, and an service water pumps P-148A and P-la8C, while the Trojan unit was opera-ting at 100% capaci:y. All except one of the measured buses (323, a 180V greater than 29% of :he saximum expec:ed bus load.0 MCC) were loaded at Sus 323 was loaded at 19%.

The seasured generator voltage and :he sessured loads were used in :he analysis program :s determine :he bus and :he equipment vol: ages. The i

r nessured vol:4ges were : hen compared to :he calcula:ej vol: ages.

The in21-

, sis program ac:urately models :ne class IE dis:ribu: ion system. as :ne calculated and :he sessured voltages were wi:hin +0.58% of eacn sener.

5.0 EVAL'JATION Six review positions have been es:ablished from :he NRC analysis guide-lines and :ne documen:s listed in Section 2 of :his repor:. Each review posi: ion is s:sted below followed by an evalua: ion of :he licensee suos:::als.

Position 1--Wi:n :ne minimum expec:ed off site grid vol: age and maximum

• Jad condi: ion, each off si:e source and dis:ribu: ion sys:es :enne:: ion omainia: ion sus: be capable of s:arting and of continuously opera:ing all

lass lE aquipmen: wi:hin :he rated equipment vol: ages.

?GE has shown, by analysis, :ha: the Trojan uni: has suffician: ca$a-oili:y and :apaci:y for s:arting and continuously opera:ing :he safe:y related loads.

Posi: ion 2--Wi:n :he maximum expe :ed offsite grid voltage and minimum load condition, eacn offsite source and distribution sys:em connec: ion

omaina: ion sust be capable of continuously operating the raquired : lass IE aga:pment wi:hou: exceeding :he ra:ed equipment vol: age.

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?CE has snown, oy analysis, tha :he voltage ra:ings of :he : lass lE l

eqaipmea: are not exceeded.

l Pasi: ion 3--Loss of of f si:e power :o ei:her of :he redundan: class '. E 1.s:ribu: ion sys:ess due :o operation of vol: age protec: ion relays. =us:

accur wnen :ne offsi:e power source is wi:hin analy:ed vol: age lisi:s.

no:

l EG&G Idano, Inc., wi'1 verify. in a separate repor:, :ha: :ne require-nen s of :nis posi: ion are sa:isfied (2AC No. 07323).

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o Position L--The NRC letter requires that :est resul:s verify :ne securacy of :ne voltage analyses supplied.

PGE has supplied the required information which shows :he calcula-

ions :o be conservative for all of tne class IE buses and loads. The :est was performed using the unit auxiliary transformer rather than the start-up

ransformer. However, :ne analysis cases using both :ransformers are in close correlation, so the test results are considered valid.

Posi: ion 5--No event or condition should resul: in the simultaneous or consequen:ial loss of both required circui:s from :he offsi:e power ne: work

o the onsi:e distribution system (GDC 17).

PGZ has analyzed tne Trojan connections to the offsite power grid, and determined that no potential exists for violation of GDC 17.

PCE s:ates:

"As designed, the offsite power source does not violate (the) GDC 17 requirement to provide :wo pnysically independent circuits designed and located to assure a reliable offsite power source for the Trojan plant."

Posi: ion 6--As required by GDC 5, each offsi:e source

• shared between uni:s in a mul:i-unit station must be capable of supplying adequate scar:ing and operating vol: age for all required class 1E loads with an accident in one unit and an orderly shutdown and cooldown in the remaining units.

This applies :o multi-uni: plants. It does not apply :s :he single-2ni: Trojan station.

6.0 CONCLUSION

S The analyses submic:ed by PGE for :his review were evaluated as stated in See: ion 5 of :his report. These submi::als show:

a.

See:ica 3.1.1 of IEEE Standard 208 persi:s :he use of a single sour:e af offsi:e power :s be shared between uni:s of a multi-uni: station.

5

1.

The test used to verify the analysis shows the analyses to be an accurate representation of ene worst case conditions anayzed 2.

Voltages within the operating linics of cne class IE equipment are supplied for all projected combinations of plant load and offsite power grid conditions 3.

PGE hcs determined that no potential for either a simultahous of Consequential loss of both off site 'ower p

sources exists.

However, PGE has not verified that the voltage transient caused by starting

'arge non-class LE loads will not shed the class IE buses during a safety injection. EG&G Idaho, Inc., is performing a separate review of the under-voltage relay protection at ene Trojan station. This will evaluate the relay setpoints and time delays to determine that spurious tripping of :he safety related loads will not occur with normal offsite source voltages.

7.0 REFERENCES

1.

NRC letter, William Gamaill, to All Power Reactor Licensees (Except Humooldt Say), " Adequacy of Station Electric Distribution Systems Voltage," August 8, 1979.

2.

?GE letter, C. Goodwin, Jr., to Director of Nuclear Reactor Regulation, dated Octooer 5, 1979.

3.

PGE letter, G. Goodwin, Jr., to Director of Nuclear Reactor Regulation.

dated January 11, 1980.

PGE letter, G. Goodwin, Jr., to Director of Nuclear Reactor Regulation.

dated Fe'oruary 25, 1980.

5.

PGE letter, C. Goodwin, Jr., to Director of Nuclear Reactor Regulation.

datec June 30, 1980.

i.

Telecon, C. Trammell, U.S. NRC, A. Udy. EG5G Idano. Inc., Ren Murakami.

PGE, September 16 and 17, 1980.

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