ML20126H043

From kanterella
Jump to navigation Jump to search
Adequacy of Station Electric Distribution Sys Voltages, Me Yankee Atomic Power Station, Interim Informal Rept
ML20126H043
Person / Time
Site: Maine Yankee
Issue date: 01/31/1981
From: Udy A
EG&G IDAHO, INC., EG&G, INC.
To: Shemanski P
Office of Nuclear Reactor Regulation
Shared Package
ML20126H035 List:
References
CON-FIN-A-6256 EGG-EA-5324, NUDOCS 8104030137
Download: ML20126H043 (12)
v • d • e


Text

{{#Wiki_filter:,i 4 m_.m m O p E toeho tac Fonu EG4G-396 f @ev tb7m INTERIM REPORT Accession No - Report No. EGG-EA-5324 Contract Program or Project

Title:

Electrical, Instrumentation and Control Syste: Suppert Subject of this Document Adecuacy of Station Electric Distribution System Voltages, Maine Yankee. Atenic Power Station, Docket No. 50-309, IAC No. 12774 Type of Document: Informal Report Author (s): A. C. Udy Date of Document: January 1981 Responsible NRC Individual and NRC Office or Division: [ Faul C. She=anski, Division of Licensing i This document was prepared primarily for preliminary orinternal use. it has not received full review and approval. Since there may be substantive changes, this document should I not be considered final. EG&G Idaho, Inc. Idaho Falls, Idano 83415 Prepared for the U.S. Nuclear Regulatory Commission Washington, D.C. Under DOE Contract No. DE-AC07 761001570 NRC FIN No. A6256 INTERIM REPORT ts104030 M

d ADEQUACY OF STATION EIICTRIC DISTRIBUTION SYSTEM VOLTAGES MAINE YANKEE ATOMIC PC'aT.R STATION Docket No. 50-309 January 1981 A. C. Udy Reliaoili:y and Statistics 3 ranch Engineering Analysis Division EG&G Idaho, Inc. TAC No. 12774

4 ABSTRACT The Nuclear Regulatory Co==ission has required all licensees to analyze the elec:ric power system at each nuclear s:ation. Th;. review is to deter-siae if the onsite distribution system, in conjunction with the offsite power sources, has sufficient capacity and cspability to automatically start and operate all required safety loads within the equipment voltage ra:ings. This Technical Evaluation Rerort reviews the submittals for the Maine Yankee Atomic power Station. The off site power sources, in conjunction with the onsite distribution system, has been shown to have sufficient capacity and capability to auto- =a:ically start, as well as continuously operate, all required safety loads .i:hin tae equipment rated voltage limits in the event of ei:her an antici-pa:ed transient or an accident condi: ion. FOREWORD This repor: is supplied as part of tne selected Electrical, Instru-centation, and Control Systems (EICS) issues program being conducted for

he U.S. Nuclear Regulatory Co= mission, Office of Nuclear Reactor Regula-
ion, Division of Operating Reactors, by EG&G Idaho, Inc., Reliability and Statistics Branen.

The U.S. Nuclear Regulatory Co==ission fundad the work under the ca:nari:a:ica entitled " Electrical, Instru=entation, and Control Syste= Support," 3&R 20 19 01 03, FIN No. A6256.

-CONTENTS 1.0 IKIRODUCTION'. J. 2.0 DESICN BASIS CRITERIA. 1 3.0 SYSTEM DESCRIPTIO*1 2 '.0 ANALYSIS DESCRIPTION 2 4.1 Analysis Conditions 2-4.2 Analysis Results.... 5 a.3 Analysis Verification 5 6 5.0 EVALUATION . 1. 7-6.0

SUMMARY

7.0 REFERENCES

7 APPE QIX A-TORQUE-SPEED CURVE FOR 180V SERVICE 'n*ATER PUMP. 9 l FIGURE i 1. Maine Yankee Atomic Power Statien, One *.ine Diagra=, 3 TABLI 1. P.aine Yankee Atomic Power Station Class lE Equipment Voltage Ratings and Worst Case Available Load Ter=inal Voltages. 4 l,

b ADEQUACY OF STAIION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES. ^ MAINE YANKEE ATOMIC P0k'ER STATION 'd

1.0 INTRODUCTION

An event at the Arkansas Nuclear One s:a: ion on September 16, 1978 is. det -ibed in NRC IE Information Notice No. 79-04. As a result of this event, atation conformance to General Design Criteria (CDC) 17.is being quest 2oned at all nuclear power stations. The NRC, in the generic letter of August 8 1979, " Adequacy of Station Electric Distribution Systems Volt-- ages,"1 requ, ired eacn licensee to confir=, by analysis, the adequacy of the voltage at the class 1E loads. This letter included 13 specific guide-lines to oe followed in deter =ining if the voltage is adequate :o start and continuously operate the class 1E loads. Maine Yankee Ato=ic Pcwer Company l and subsequent questions with let-(MYAPCo) recponded to the NRC letter ters of February 29, 19802 and June 30, 1980.3 Based on information supplied by MYAPCo, infor:ation found in the Final Safety Analysis Report (FSAR), and a telephone call'of Oc:ober 1, 1980*, :nis report addresses the capacity and capability of the as. site - distrioution system of the Maine Yankee Atomic Power Station, i' :onjunc-tion with the off site power system, to =aintain the voltage for :he required class 1E equipment within acceptable limits for the worst-case starting and load conditions, 2.0 DESIGN 3 ASIS CRITERIA The positions applied in determining the acceptability of the offsite voltage conditions in supplying power to equip =ent are derivod from the following: 1. General tesign Criterion 17 (GDC 17), " Electrical Pewer Systems," of Appendix A, " General Design Criteria for Nuclear Power Plants," of 10 CFR 50. 2. vaneral Design Criterion 5 (GDC 5), " Sharing of Struc-ture s, Systens, and Co=ponents," of Appendix A, " General Design Criteria for Nuclear Power Plants," of 10 CFR 50. 3. General Design Criterion 13 (GDC 13), " Instrumentation ~ and Control," of Appendix A, " General Design Criteria for Nuclear Power Generating Stations." 4. IEEE Standard 308-1974, " Class 1E Power Systems for Nuclear Power Generating Stations." 5. Staff positions as detailed in a le::er sent to the licensee, dated August 8, 1979.1 1 6. ANSI C84.1-1977, " Voltage Ratings for Elec:ric Power Systems and Equipeene (60 Hz)." 1

-.. ~ b 4 t Six review positions.have been es:ablished from the NRC analysis guide-linesl and the above-lis ted documents. These are stated in Section 5. 3.0 SYSTEM DESCRIPTION Se:: ion 3 of the Maine Yankce FSAP'and :he a::achments of references 2 and 3 discuss :ne onsi:e distribution system. Figure 1 of :his report, is a si=plified unit one-line diagram of the Maine Yankee electric distribution sys:e= :aken from Reference 4. t i, i Figure 1 shows that the class 1E 4160V' buses 5 and 6-are rupplied power fro: auxiliary buses 3.and i, respectively. 7 hen the unit generator is operating, these bases are powered by ::ansfor:er x24.. Upon loss of the - uni: generator, buses 3 and 4 (and hence class 1E; buses 5 and 6) are auto-matica11y :ransferred5 to re:sive power fro = the 115kV grid via s:artup transfor=er x14; non-class 1E, 6.okV buses au:omatically transfer to startup transfor=er x16. The unit generator can be isola:ed from auxiliary trans-for=er x i and tha =ain_ transformers enah'ing the: :s supply offsite power to :he class lE buses as a delayed second source from, the 345kV grid. Bus, 5 can also be powered by tertiary windings of star:up transfor=er x16. platt procedure No. 1-22-3 preven:s use of. :nis scurce except when all o:her scur:es of AC power-have failed. j Ea:h 4160V class lE bus supplies power for a 180V class 1E ' bus (Nos. 7 and 8) via separate 4160V/480V transfor=ers. 10V vi:a1 buses are'sup; lied powe "-'nterruptacle power supplies (U?S),3 which auc tioneer power fro = s:a: ion batteries or 480V buses 7 or S. MYA?Co supplied :he equip =ent operating ranges identified'is Table 1 of :his report.) The FSAR shows : hat station 125V 'O buses supply power - for :ne 4160V class IE motor control circuits. l-; 4.0 ANALYSIS DESCRIPTION-5 .1 Analysis Conditions. MYAFCo has anclyzef all but one offsite source connection to the onsite distribution syste= under extremes of load and offsite vol: age conditions :o determine the ter=inal voltages. o 1E equip =e:t. However, MYAPCo did not provide analyses for bus 3 receiving i power from transformer x16 as the connection is no: required by GD0 17, and i it is no: credi:ed in the FSAR as being a source of offsite power. The, l M' APCo vol: age analyses show that: J I j 1. Tne maximu= load ter=inal voltage occurs during unit' i shutdown when transformer ~x24 carries :he =inimum auxiliary and class 1E loads with the 345kV distri- [ bution system at its maxi =um voltage of 262kV. 2. The minimum steady state load terminal voltage occurs when an accident occurs without loss of offsite' power with transformer x14 carrying the maximu= auxiliary and

lass 1E loads with the 115kV distribu: ion system at t

i:s :inimum continuous voltage of 116.5kV. 2 v w,,.,w --eev y-w-,.+.y.3.>.,, ww f.,.,.-.,r., y e w y.-y,..%.,,w.-r,,w,#,--.-w-- .,,+mi-.,w.em.,-ww = ,,m-,%%-m,-1.,+.,..wwe,,,s_w.,.wi-,n,..,,...e-,.v. .vvm

5 2 4 1 I 4 v o c a c u u n a j 2 l l )l s s [ l "y s ti ua c = n v s o i c l u I e n 4 a I I I l c o ( v n n s o I ) l i 1 I l s 8 s 4 3 u 6 l a s a o c y n l ~ v n wWw ) o a N I e I y g e AAw s l s c c a n e l ) t I I I I 2 I y s s u u 4 s o 1 v e 4 v a s o y 1 s u e j t o m 4 g s v c c g[i e o a n

  • w e

H )(- s l ) c I I I t Mfs I s u 4 e l n a l j u l SE 1 1 I o G o AYY i S r4 m u D s v { t i a o G t;nE h l 1 I Aid e I f Fs I 4 l e E I l I l R y l 0d l o o o u u n i Pl i ii G h ) f ls l l o i l Yln f l r I I I s I I o u n i R "A-A S s A l I 1 I e c l c itIi V n G n y s O ids f l D s I o K )I X i-I u I e l r i a 4 An 5 l 4 v AYo g s o n 3 o 'l : o n s it m s ) a fi S 3 s ls I R v 4 1 u Az E o 3 s l l r_ l4 c c a c y R s a n e 0 6 I lI )I o l f e 2 i S 4 m C l t l wgT n c A i n t m l o AR 1 4 T Ay E I ) t b Pl l i 1 s h u i N R 0 s 0S O c 1 y CK T s n 4 N SN A I e o s I I I R o e G v a n u i DL E u 4 s V N ll l c o K E [ o l ) - s m 2 MM2 1 9 I l 4 T s s I 0 u 2 I 4 3 s iN m N y c c e c i i a n n o l ) )l e AN i I "y 4 m ~ w l

l1

,4:

il l;

l!li: ll

TABLE 1 MAINE YANKEE ATOMIC POWER STATION CLASS 1E EQUIPMENT VOLTAGE RATINGS AND ANALYZED WORST CASE TERMINAL VOLTAGES (: of nominal voltage) Maximum Minimum Rated Analveed Rated Analv:ed Nominal ~ ' Voltage Steady Equipment (100%) state Transient Motors 4kV Start 75 89.8a Operate 110 108.2 90 95.5 460V Start 80b 82.6: Operate 110 108.3 90 90.- Starters 480V Pi:kup 80 79.e Drop:ut 70 79.4 Operate d 103.8 80 88.5 Low v:ltage instrument and control circuitse Mrmentary mini =u= motor ter=inal voltage unen starting a ecndensate a. pu=p. This assumes the condensate pumps, heater drain pu=ps, and cir-

lating water pu=p have been previously shed.

b. Appendix A shows the torque-speed curve of the largest 480V class lE load. Mr:entary =inimum motor ter=inal voltage unen starting 460V Service c. Water pump (250 hp). d. Not supplied by licensee. U?S is powered by station batteries or rectifiers only. e. 4 ['

i. 3. The minimum transient load; ter=inal voltages occur with J the conditions of 2 (above) with the. start of a conden-sate pumpa (for the 4000V class 1E equipment) and the . start of a service water pump (for the.460V class 1E' equipment). The study accounted for cable and transformer L=pedences. Field' inspections verified the transformer. cap settings. The minimum luad ' con. sists of component cooling water pu=ps, lighting, and some unspecified. 430V ' loads. KYAPCo assumed,a constant 120kV at the source connections due to automatic load capchanging2 autocransformers located there, while the Maine Yankee Atomic Power Station switchyard voltage was. free to follow the load demand. 4.2 Analysis'Results. Yaole 1 shows the worst case class 1E equip-ment terminal voltages identified in the'MYAPCo analysis. The worst-case motor starting' voltage transient condition will last only while starting. tue 2500 hp condensate pump. At the ndnimum voltages identified in Table 1, j no contactors will drop out to cause spurious tripping of' loads.3 Con-tactor pickup is prevented until the voltage recovers. 4.3 Analysis Verification. MYAPCo measured-the grid, generator and bus voltages, and the attual load of the buses and selected equipment. This was done twice, with the transformer loading as follows: Loading (% of rated) ? Transfor=er Test 1 Test 2 Buses Supplied e x24 (4160V) 63.4 65.6 3, 4, 5(1E), 6(IE)* x26 (6900v) 95.2 96.0- . 1, 2 C x507 (480V) .68.0 66.9 7(1E) x608 (480V) 58.0 58.8 8(1E) i

  • Buses 3 and 5 are located adjacent to'each other. and the study considered them at identical potential, with separate load groups.. Buses 4 and 6 are the same.

i Analyses were done using the measured generator source voltage and the 1 measured loads, and the results compared with the measured. bus voltages. l i e I e a. This pump was studied as the largest load on the same transformer that I supplies power to the class 15 buses. Although larger motors are in service at the Maine Yankee Atomic Power Station, they use 6.9kV from l separate transformers.3 I l 5 P s-. .v w,w-,y.,emw e,, m e. ,,,.s .v---. e._,,e...- + =vv..-e. --.-,e..-w ...m.,... - - -. - -, + - - -.. -. m e-

m--

i l Two comparisons were made which show the analysis to be within +1.30/ -2.42% of the actual measured bus voltages for the class lE buses. For all buses, the deviation was within +1.30/-3.56%. A negative figure indicates tne actual measured voltage is higher than the predicted voltage. enat 5.0 EVALUATION Six review positions have been established from the NRC analysis guide-linesl and documents listed in Section 2.0. Each review posi: ion is stated below, followed by the evaluation of the licensee submittals. Position 1--With the minimum expected offsite grid voltage and maximum load condition, each offtite source and distribution system connection combination must be capable of starting and of continuously operating all class lE equipment within the rated equipment voltages. MYAPCo has shown by analysis that the Maine Yankee Atomic Pcwer Sta: ion has sufficient capability and capaci:y for starting and continuously eper-ating the class IE loads within the equipment voltage ratings (see Table 1). However, MYAPCo has not analy ed for when the tertiary winding of :he ::ans-for=er x16 supplies power to class lE bus 5. Position 2--With the maximum expected offsite grid voltage and minimu: load condition, each offsite source and distribution system conne::icn ccebination must be capable of continuously operating all class 1E equip-ment without exceeding the rated equipment voltage. P MYAPCo has snown by analysis that the voltage ratings of the c.' ass lE equipment wil'. not be exceeded. MYAPCo states that even if a switchyard vol: age of 124kV (4kV higher than the maximum expected voltage) was present,

na: no load would have its voltage limit exceeded.3 Position 3--Loss of of fsite power to either the redundan: class lE ditrioution systems or the individual class 1E loads, due to opera: ion of vol: age protection relays, must no: occur when the offsi:e power source is rithin ar.alyzed voltage limits.

9 EGSG Idano, Inc., will verify, in a separate report, that the raquire-men:s of tnis position are satisfied (TAC No. 10032). Position 4--The NRC letterl requires that test results verify the accuracy of the voltage analysis supplied. 2 MYAPCo has supplied the required information," which shows the calculations to be an accurate representation of the class lE buses and loads. The test was performed using the unit' auxiliary transformers; how-ever, since the case studies using the unit auxiliary and the startup trans-formers are in close correlation, the test results are considered valid. Position 5--No. event or condition should result in the simultaneous or consequential loss of both r3 quired circuits from the offsite power ne:verk to the onsite distribution system (CDC 17). 6 6 -=

' l MYAFCo has analyzed the Maine Yankee' connections to the.offsite power grid and has determined that no potential exists for the simultaneous or consequential loss of both circuits from the offsite grid.2 ~ Position 6--As required by CDC 5, each offsite ' source shared between units in a multi-unit station must be capable of supplying adequate starting l 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. This ' applies to multi-unit stations. It does not apply to the single-unit Maine Yankee station. 6.0

SUMMARY

The analyses submitted by MYAPCo for this review vere evaluated as stated in Section 5.0 of this report. It was found that: 1. Voltages witnin the operating limits of the class 1E-equipment are supplied for all normal comoinations of plant load and offsite power grid conditions. However,'the NRC should require the MYAPCo to incorpor-ate limiting conditions of operation in the unit Tech-nical Specifications that restrict use of the bus-5 feeder from the certiary windings of transformer x16 as prescribed in Plant Procedure No. 1-22-3. 2. Tne test used to verify the analysis shows the analysis to be an accurate representation of the worst case tonditiens analyced. 3. MYAPCo has deter =ined that no potential exists for eitner a simultanous or a consequential loss of both offsite power sources. EG&G Ida42, Inc., is performing a separate review of the undervoltage relay protection at the Maine Yankee station. This will evaluate the relay setpoints and time delays to determine that spurious tripping of the class lE ouses will not occur with normal off site source voltages.

7.0 REFERENCES

1. NRC letter, William Gammill, to All Power Reactor Licensees (Except Husboldt Bay), " Adequacy of Station Electric Distribution Systems voltages," August 8, 1979. 2. MYAPCo letter, Robert H. Groce to Office of Nuclear Reactor Regulation, U. S. KRC, " Adequacy of Station Electric Distribution System Voltages," Feoruary 29, 1980. 3. MYAPCo letter, Robert H. Croce to U. S. NRC, " Request for Additional I Information on Adequacy of Station Electric Distribution System Volt-ages," June 30, 1980. s r ) w-y g-y air y w f =f +ww+i vv-W br-< we' my .W y-e.-m-y n-e a v ge--- c--euof -w mywe w y+amm +W r W

4. Telecon, A. C. Udy, EG&G Idaho, Inc., P. Johnson, Yankee Atomic Elec-tric Cosspany, October 1,1980. 5. Yankee Atomic Electric Company report No. 1204 " Auxiliary Power System Voltage Study for Maine Yankee Atomic Power Station," dated February 28, 1980, attachment to Reference 2. 8 " a p y, y $W'# M + 'F +* *

. _ _ ~ I t ..q r l .m. _....... q O I l .C_ ..a_._. E

e. '.I
q..;

1 _r h y. -,. .J. .i.. bi.D- } s, .7... } -\\ 4 7. I g 'g A _ '. a

  • m a.....

......1 7p......-.t ,x .$...... j ..y g 4. c,, . p _..... f E s t e ._ 3 a ..L ... /'

r. L...,.. > a e

a r .k.

c..e

..U. ,.___i s c .0. ,hd 4 3 w" u l-t i a W g 6 4 p'Q ey a 3 e ' f.a3 s ,3 1 I 4 4.... L ,g lll* 2 t' . E p ' C. f Cu - k (El .A .q. ...r e , d i.. , *t 7 y c p, U K ......_.1 .b ..L. 3 ar! j q , ;p. N \\... ' w. . _. v

a..

1... I ybg -).- g 3 g J .g.._. ,,1-to T_4- = .. J

g C

t4 g g \\.. m m. V1 s Mg s. 4 - } -{. >g. i

  • A E

D, k *5 W }

s. a..

~ u d .=.e c e.= G k M \\ , O. i =8 .no g 4--..-.. c, r* .a f. c., O F 7 G. g a L 'ao "as M e \\. aC W,, " h l ~g* \\ >2 "s.. . \\. ---..g U .m,,, = r, -w ,\\ s \\ s., J o Q ^,a ' ' ' * * \\ \\ .e ^%... .s. \\

}\\.. ).

O,,,,, ins j==,. .O,a_b. - Y e .a y c. = = - y) m W..e _.A# ~ W E 3 e. L - V - i ~

  • E s-t ey~

y _ *C D a l C g 8 i L. c.e. g w m } gy

y.... g.

= Y .= w a...P. .o, O _.. .k s .y N r q =a. ..n. 3 e g g r: m

64. *3..,.

M....' J.-.. w I~._. C n a t d ar-- 3 g 0 b. 3,. ).. ..-.g p.L. f n. _t...e

1. 3 L...s.

, g.. o e j g.. g 7 _.4.. a g. .4..... g t-y o - ---wr r 3 <e e i, = 'P-'-E T. . h. _.. : = } nw c I1 as >O. u g e, . L.a. k.. ' re. of . c:qg ..,7..... .. g. .-Q -.. 24

  • 3 m

.e ea y 7 p g n. r UTC'scl.~

  • NC'1 - tMI lain _id

' " ~ a.. e.. 9 f &s $. 9 s e 94.. Si a*. e . A i n.. ..,w. --..-,o}}

Retrieved from "https://kanterella.com/w/index.php?title=ML20126H043&oldid=4274103"