ML19240C000

Adequacy of Station Electric Distribution Sys Voltages, Technical Evaluation Rept

ML19240C000
Person / Time
Site:	Cook
Issue date:	03/31/1981
From:	Weber D EG&G IDAHO, INC., EG&G, INC.
To:	Shemanski P Office of Nuclear Reactor Regulation
References
CON-FIN-A-6429 EGG-EA-5339, NUDOCS 8104170710
Download: ML19240C000 (11)

Text

EGG-EA-5339 M u ch 1981 ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM

~

VOLTAGES, D. C. COOK NUCLEAR PLANT, UNIT NOS. 1

. AND 2 Ah 9 D. A. Weber N'

RC Researc1 anc ec1nica gsr

,wh N Ass. :stance Repor: a# w we /Q a "

4 A

v. .

o U.S. Department of Energy

• 5 Idaho Operations Office

• Idaho National Engineering Laboratory

c .

I ppa

..efif p Q, f.W< %

tMf.,%:y L J s

gg

~q'19p 4 sc %fgV }aQGP p

s 'yu,;

g, ..b bMA .[.x y:.3 -

1}5y*

N ,

4 f,. ?Ng '?> k.zl g H. J Ms

[ e:rn(f 8 ""r F N, mra rans17parr any,

~0,

,pg gj g i L

$ Sh f,hY'bf, W O gg . f.'.g .,y? wuma: vannr ance vama 5mama 4=

M q

7 .y 'ye e

< ,,,,.,st',

. . - ,,.:rd

,mnur'aE nli y ww=*

n

""** WM > " o m

+

y- y E &, + %% ' M @ *""' ~M~$[basiwmettv

@Wrill[

• w=-w' nNr* s"r-

'~= ~ " # "

m. , :,gy .F gy m , .w: ..,,, . -

- ~~ - - ~

,g,.

d ik/

}

}

D'6.% ' ' ' O.,g""G:M et.r .m mW.. "_

~. -

~~

'~ *

.i.u.,wami . .c ly:1

!$ ; & a ~ ~-w4 e

.1 pa c; e W STM N RNy CTNgge.,5Q g C'g$

fs idea,G m % ..g.. 9 w d. L -.~ #

m pNg,d qm m &ra-q' i e%,g Q f h.Yh d %v.-.e  %. gu, W ..;x.. w%;c,g% g%D

.a , , g., q ,,

?5E5SSN2f.Ag?h.%c, b$ W $ SN~n #y $p#,  ;; %dr

??

q%$~&t, n

98Ml455Nt [

>M C":'*.:. d :ksc d y

%wgp.

Te'Ebe#C46tEtjk r

t.7,g;i b Q7 M N b5? h QIAl~ N;~UiM E$f rX2 di M, w d4og.gM

. @by N$$

~c*jQ QsgN):?%

f6%ZDAD kg This is an informal report intended for use as a preliminary or working document I

HC 'Reseatch and ~iechnica Assistance Report Prepared for the U.S. Nuclear Regulatory Commission y Under DOE Contract No. DE-AC07-76ID01570 6 6 E 6 mano FIN No. A6429 alo4 no Hb

hEGnG.o........

.-,w. ,

Itew 11 7%

INTERIM REPORT Accession No ___ _ _ - _ _ .

Report No- EGG-L A- a H 9 Contract Program or Project

Title:

Selected operating Reactors Issues Program (III)

Subject of this Document:

C. Cook Nuclear Adequacy of Station Elect ric Distribution System Voltages, D.

Piant, Unit Nos 1 anr! 2 Type of Document:

'Icchnical I.va l uat ion Repor t Author (s):

D. A. Weber b

N3RC Resem e "m}d r

Date of Document:

" " " " ~

- Assistance Report Responsible NRC Individual and NRC Office or Division:

Paul C. Shemanski, Division of Licensing T his document was prepared primarily f or prehminary or internal use it has not received full reuew and apptosal Since there may be substantive changes,this document shou d n( t be considered final.

FGSG Idaha, Inc idaho Falls. Idaho 83415 Prepared for the U S Nuclear Regulatory Commission Washington, D.C.

Under DOE Cor. tract No. DE-A007-761D01570 NRC FIN No. A6429 __

INTERIM REPORT

0315J ADEQUACY OF SI'ATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES D. C. COOK NUCLEAR PLANT UNIT NOS. 1 AND 2 Docnet Vos. 50-315 and 50-316 iarch 1981 D. A. Weber Relianility and Statistics Branch Engineering Analysis Division EG6G Idaho, Inc.

NC Researca anc :ec'1nica' Assistance Report TAC Nos. 13111 and 13112

ABSTRACT Trae Nuclear Regulatory Commission has required all licensees to analyze tne electric power system at each nuclear station. This review is to deter-mine if toe onsite distrioution system in conjunction with the offsite power sources has softicient capacity and capability to automatically start and operate all required safety loads within the equipment voltage ratings.

This Teconical Evaluation Report reviews the submittclo for the D. C. Cook Nuclear Power Station.

The oftsite power sources, in conjunction with the ensite distribution system, n.sve beca shown to have sufficient capacity and capability to con-tinuously op. rate all required safety related Icads, within the equipment rated voltage limits, in the event of either r. anticipated :;ansient or an accident condition upon completion of changes noted in Section 4.1.

FOREWORD This repo.t is supplied as part of the " Selected Operating Reactor i f r. o e s Program (111)" being conducted for the U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation, Division of Licensing, by EG6G Idaho, Inc., Reliability and Statistics Branch.

Ihe U.S. Nuclear Regul 1 tory Cormni s sion funded the wor k under the authorizattoo, B&R 20 19 01 06, FIN No. A6429.

J ii

CON TE NTS 1.0 'NTRODUCTI.N ...................................................... 1 2.0 DESIGN B ASIS CRI'IERIA ............................................. 1 3.0 SYSTEM DESCRIPTION ................................................ 2 4.0 ANALYSIS DESCRIPIION .............................................. 2 4.1 De si gn/ Ope r a t ion Caanges ..................................... 2 4.2 Analysis Coaditions .......................................... 2 4.3 Analysis Results ............................................. 5 4.4 Analysis Verification ........................................ 5 5.0 EVALUAfION ........................................................ 5

6.0 CONCLUSION

S ....................................................... 7 7.0 REI'ERE::CES ........................................................ 7 FIGURE

. 1. D. C. Cook Unit I elect;ical single-line diagram .................. 3 TABLES

1. C l .a s s lE Equipment Voltage Ratings and Analyzed Worst Case Load Terminal Voltages ........................ 4

2. Comparison of Analyzed (31tages and Undervoltage Relay Setpoints ...................................... 5 VRC Research and Tec1nica

. Assistance Report iii

ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYbfEM VOLTAGES L C. COOK NUCLEAR POWER STATION UNIT NOS. 1 AND 2 1.0 INfRODUCTION An event at the Arkansas Nuclear One station on September 16, 1978 is described in NRC IE Inf onnation 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 August 8, 1979, " Adequacy of Station Electric Distribution Systems Voit-ages," I required each licensee to confirm, by analysis, the adequacy of the voltage at the class IE loads. This letter included 13 specific guide-li ne s to be followed in determining if the load terminal voltage is adequate to start and cantinuously operate the class 1E loads.

In re s pon s e to the generic letter and questions from the staff, Indiana and Michigan Electric Company (IHECo) submitted information and analysis on Decemaer 17, 1979,2 May 28, 1980,3 and Januar* 27, 1981.4 These submittals, the EG6G Idaho, Inc., report on the D. C. Coor Unit 1 degraded grid protec-tion,> and the D. C. Cook Unit 1 Final Safety Analysis Report complete the i n t o nna t i on reviewed for this report.

Based on tne information supplied by 1MECo, this report addresses the capacity ud capability of the onsite distribution system of the D. C. Cook

. Nuclear Power Station, in conjunction with the offsite power system, to maintain the voltage for the required class 1E equipment within acceptable limitt for tne worst-case starting and load conditions.

The discussion and evaluation which follows will apply to both units.

2.0 DESIGN BASIS CRITERIA The positioas applied in determining the acceptability of the offsite voltage conditions in supplying power to the class 1E equipment are derived f rom the f oll owing:

1. General Design Criterion 17 (GDC 17), " Electrical Power Systems,"

of Appendix A, " General Design Criteria for Nuclear Power Plaats," of 10 CFR 50.

2. General Design Criterion 5 (GDC 5), " Sharing of Structures, Sys-tems, and Components," of Appendix A, " General Design Criteria for Nuclear Power Plants," of 10 CFR 50.

3. General Design Criterion 13 (GDC 13), " Instrumentation and Con-trol," of Appendix A, " General Design Criteria for Nuclear Pcwer Pl ant s ," of 10 CFR 50.

a~ IEEE Standard 308-1974, " Class 1E Power Systems for Nuclear Power Geaerating St ations."

~

NC lesearc1 anc ecmica A J . i s.c-we+

tsi ,n.co poner+

s asupVIL 1

5. Staff positions as detaixed in a letter sent to the 'icensee, da ted Augu st 8, 1979.1

6. ANSI C84.1-1977, " Voltage Ratings for Electric Power Systems and Equ i pne nt (60 Hz)."

Six review positions have been established from the NRC analysis guide-linesl and the above-listed documents. These positions are stated in Section 5.0.

3.0 SYSTEM DESCRIPflON Figure 1 of tuis report is a simplified sketch of the D. C. Cook Unit 1 single-line diagram.

Both safety trains of each unit can be supplied from three sources:

the " normal", "p re f e rred", and "al t e rnate" auxiliary source s .

With the unit producing power, the " normal" auxiliary power to each satety train is supplied from the unit generator via transformers 1-AB and 1-CD (2-AB and 2-CD for Unit 2). A unit trip results in automatic transfer to tne "pieferred" auxiliary source via TR-4 or TR-5 and TR-101-AB and TR-101-CD (TR-201-AB and TR-201-CD for Unit 2). After the unit generator disconnect links nave been removed, the safety buses can be supplied from tne " normal" auxiliary power source via TR-1 (TR-2 for Unit 2). TR-12-EP is an " alter.ute" auxiliary power source to both units.

Eaco 4100V bus supplies power to the 4kV motors, 600V load centers and motor control centers (MCCs), and the 575V motors and loads. The breaker control circuits for the 4160V switchgear and the 600V load centers are

applied oy tne station batteries and are independent of grid voltages.

The MCC contral circuits receive their control power from individual control power transformers.

1HECo supplied the eq ui pmen t operating ranges identified in Table 1.

4.0 ANALYSIS DESCRIPTION 4.1 Desi gn/Operat ion Gnange s. The voltages shown on Table 1 are based on the f ollosing licm.see proposed changes:2

1. Co :in ge the tap setti M on TR-12-EP (alternate power source) from the 07kV tap to the (,d.8kV tap.

2. Install undervol t age protec tion on the 4kV buses A and D for Unit I and 2 witn a vol tage setting of 89.9% for two minutes.4

3. Mauity the exi s ting undervol tage rel ays at the AkV buses for a voltage set ting of 79.9% for two seconds.

4.2 Ana l y s i i, Conditions. IMECo has determined by load flow studies anJ review of nistorical data tnat the maximum expected offsite grid vol- ,

tage is 795.okV, 370kV, and 72.45kV and the minimum is 744.35xV, 347kV, and 64.86KV on the 765k7, J70kV, and 69kV offsite sources, respectively.

2

T I

N U2

' Q O,,D~ 5 -

V k

5 6

7 d O.s L R

O T

O&"~NE%"%F=~ E

• e =I

,T Um D y r [ ,h'wI^ -

p' D

r. 1

. Av D ' C 1

1 R

0 i T 2

.}_ 9

_ C '- w

/N f

,O2iL.I, h w V -

k 5

4 3

fl -

E C

Wa v yl D 1

D l

l D

l R B T I U L v' A Lc1 . . L O _

S 0 _ D N D

E 2 _

Qv1C I A

R

- R T .

R m E __ a r

- F _

E R . _

. - v P

'3<

- o f -

t  ;

i

> L _ -

m - ,

Av"C n D

- ' ' 1

/

,qT x m i l

0 -

- e C 1

. NN C 1

C 1

C l

l 0 l

g 1 1 n

- R 1 T T i s

1

, 1:

V . , - _ c B

k 5

4 i ,i ,bMf_ !1 $ , t l

l i

r

- s5 t 3 > %A B R c R T e T 1 l 0 -

1 f o

' - sm k i

c b f6 o s

jf B

~

y em I C

C o

_ B l B 1 i l T D

' r ii  ! l A

- '.v . D ,, B N

..C 1

'D f A

l I

1 A e R r LE T u AC g MR i RU F OO -

NS  !

if v

_. t n O2 i Lm U j ' q

+ 3 iIf /)1L wm V -

B V 1 k - A - L 5

k .T R

6-2 1

T .I T

AV L E

A l

E V

4 o is

• l'b' I m N 1 k 4 AVV l

AI 1

3 NlU2 .d i

U lkE ~t 1 lhL 1V O T 0 T 0

. 6

{

k'! .,

_ i' 9

6 t

'_ N

- ]i i!

) ;f: /

Uv -

E TE FE 2 AC 3S 1

p NR EU RU B Rg EO T TS L '

A

TABLE 1 CLA3S lE EQUIPMENT VOLTAGE RATINGS AND ANALYZr.D WORST CASE TERMINAL VOLTAGES

(% of nominal voltage) a . . b Minimum Maximum -

Analyzed Igui pme ra Condition Rated Analyzed Rated Steady State Tranaier:t 4000V Motors Start -- --

65 --

67.3 Operate 110 111 90 93.3 --

575V Motors start - --

85 --

78.1 Operate 110 107 90 90.1 --

500V Starters r'i c k u p -- --

85 -

78.1 (57W base) Dropout -- --

70 --

78.1 Operate 110 107 90 90.4 --

Other Equipmsat'

a. 69kV " alternate" auxiliary source at 105%.

o. 345kV " preferred" auxiliary sources at minimum of 100.6%.

c. All of: 2r safety-related electrical, instrumentation, and control equip-ment ;< quired for safe snutdown will operate properly within a voltage raoge of 90% to 110% of naminal or of the 575V base as splicable.

1MEco has analyzed eaco offsite source to the onsite distribution syst em under extremes of load and offsite voltage conditions to determine the terminal voltages to IE equipment. Tbc sorst case class IE equipment terminal voltages occur under ?< silowing c :nditions:

1. The maximum valts7,= accurs when the 69kV "alte nate" source is at its maximam expected value and supplying the accident loads of ine unit and the shatdown loads of the other unit with TR-12-EP applying one train i n ea c h un it .

2. Tne minimum steady etate voltage occurs when the 345kV source is at i t s minir.am expe c ted value and TR-5 is supplying the accident laadc ai one unit and the shardown loads of the other unit.

3. The warst as transient voltages occur when the 345kV source is at i t s minimum e xpec tod value and TR-5 is supplying the accident -

laade of one unit, the shutdown loads of the other unit, and the acc; Jent laads are b u l v, started. ,

4

4.3 Analysis Result. Table 1 shows the projectei worst case class lE e qu i pmen t terminal voltages. Table i shows a comparison of the analyzed voltages with the undervoltage relay setpoints.

TABLE 2 COMPARISON OF ANALYZED VOLTMES AND

, ONDERVOLTAGE RELAY SETPOINTS

(% of nominal voltage) a Minimum Analy7ed _

Relay Setpoint Lacatioa/Reinys Voltap; Time _

loltage (Tolerance) Time 41bOV ous D b (4eV base )

D e r,' .ed grid 93.3 con t i r.uo us 89.9 + 5 2 mi n

+ 6 see Loss of grid 87.3 c 79.9 + 5 2 sec

+

._ 0.2 sec

a. License e has determined by analysis the minimum bus voltages with the offsite grid at the minimum expected voltage and the worst case plant and class IE loads.

n. Undervoltano relays ar e on bus A and D. The analyzed data is for bus D wnich represents toe worst case,

c. Transient durations nat provided, but the degraded grid undervoltage set poi nt of two minutes is long enough to override any voltage dips caus;J w tne start ing of large motors or bulk loads.

+.4 Ana;ysis Verification. During a st artup of Unit 2, while Unit I we, at paw"r, measured valtage, current,, and phase angle readings were made bv I mil at tae " preferred" offsite power substation bur, the " alternate" offsito p,wer sast at ion bus , and at the Unit 2 auxiliary buses. The measored values for current and voltages were employed as input data on tne power distribution model previously used to compute the bus voltage ievels at tne auxiliary buses. Specifically, the 345kV (TR-5 feed) bus measured voltag, and lE bus curr4ats were us:d to calculate the voltages at the 3 '. . S k V , 4kV, and 600V buses. These calculated voltages were then compared with tha actual measured voltages. The results showed a maximum 2% error at Ihe 600V tevel.

5.0 EVALUATION Six review positions have been established from the NRC analysis guide-lin-;l aad tue dx umen t s listed in Section 2.0 of this report. Each review pmition is stat ed below followed by an evaluation of the licensee subm_'tals. . Tbc evaluations are based on completion of changes described in Section -+ . l .

5

Pasition 1--With the minimum expected offsite grid voltage and maximum load condition , each offsite source and distributicn system connection combination most be capable of starting and of continuously operating all class lE egn pment within the equipment voltage ratings.

IMECo nas shown, oy anal fsis, rha: the offsite sources and the onsite distributioc. system have sufficient capability and capacity for starting and contir.aeusly operating the class lE loads within the equipment voltage .

rat.ngs (Tabl e 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 che required class lE equipment witnont exceeding the cquipment voltage ratings.

lHECo has shown, by analysis, that the voltage ratings of the class lE e q u i pmc a t will ant ae exceeded (Table 1).

Positioa 3--Loss of offsite power to either of the redundant class lE Jistribution systems due to operation of voltage protection relays, must not occur when the offsite power source is within expected voltage limits.

As snown in Table 2, voltage relays will not cause loss of class lE distribution systems when the offsite grid voltage is within expected vol- .

tage limits.

Position 4--The NRC letterl requires that test results verif:r the accuracy of the vo l t a ge analyses supplied.

Revi>w of tae test data suomitted by IMECo indicates that the original aaalysis is satisfactory. The largest difference between the measured and calculated voltage was 2; at two of the 600V lE buses with the measured voltage less tnan tne calenlated voltage. 7:he revicw considered plant loading conditions, instrumentation errors, and the 1.15 service factor for all class IE mat ors . The results are applicable to Unit 1 based on similar loading cond i t i on s and identical onsite distribution systems.

P3sition_g--Na avent or condition should result in tne simultaneous or co n s e que n t i al Ins < of both required circuits from the offsite power network to tno onsite distribution system (GDC 17).

IbiECo has analyzed the onsite connections to the offsite power grid, and determined that no potential exists for simultaneous or consequential loss of bat a circuits from the offsite grid.

Pasition 6--As re qui red by GDC 5, each of fsite source shared between onits in a multi-unit station must be capable of supplying adequate starting and operating v>]tage ter all required class lE loads with an accident in one unit and an orderly shutdown and cc,oldown in the remaining units.

ae D. C. Cook Nuclear Station is the site of two nuclear units that ca ae supplied fram these offsite sources where two of the sources are snared betweon aaits.

6

The IMECo analysis satisfies this position in that each shared of fsite source was found to be capable of supplying adequate voltages to all class lE loada with a shutdown in one unit and an accident in the other.

6.0 CONCLUSION

S The voltage analyses submitted by IMECo for the D. C. Cook Nuclear

. Power Station were evaluated in Section 5.0 of this report. Upon the completion of changes described in Section 4.1, it was found that:

1. Voltages within the operating limits of the class lE equipment are supplied for all projected combinations of plant load and normal offsite power grid conditions; including an accident in one unit and the safe shutdown of the other unit.

2. Tue test used to verify the analysis shows the analyses to have accurately determined the worst case conditions analyzed.

J. 1MECo uas determined that no potential for either a simultanous or consequential loss of both offsite power sources exists.

4. Loss of offsite power to class IE buses, due to spurious opera-tion of voltage protection relays, will not occur with the off-site grid voltage within its expected limits.

7.0 REFERENCES

1. NRC letter, William Gammill, to All Power Reactor Licensees (Except Humboldt Bay), " Adequacy of Station Electric Distribution Systems Voltage." August 8, 1979.

2. IMEco letter, J. E. Dolan, to Director of Nuclear Regulation, dated October 17, 1979.

3. IMECo letter, J. E. Dolan, to Director of Nuclear Regulation, dated May 28, 1980.

4. IMEco letter, J. E. Dolan, to Director of Nuclear Regulation, dated Janaary 27, 1981.

i. "EG6G Technical Evaluation Report on the Degraded Grid Protection for Class IE Power Systems for the D. C. Cook Nuclear Plant Unit 1,"

Rev. 1, dated August 1980.

7