ML19270G027

Forwards Revised one-line Diagram Showing Changes to Alleviate Potential Overload Situation of Electrical Sys Which Supply Offsite Power for Startup & Emergency Loads

ML19270G027
Person / Time
Site:	North Anna
Issue date:	05/23/1979
From:	Brown S VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
403, NUDOCS 7905290404
Download: ML19270G027 (3)

Text

.

THIS Docul,'EUT CONTAlHS

~ FOOR QUAUTY PAGES Vepco v44GINI A ELECT RIC AND POWER COMP AN Y, RICMMONO. vlRGINI A ;)_ g i May 23, 1979 .

Mr. Jwes P. 9'9eilly, Directer hei al No.103 PSEP.C/WLT:mac: wang Office of Inspection S Enforcement

1. S. 'lucle3r Regulato y Comission 1+n II Ncket No. '9-339

'01 Marietta Street, Suite 3103 Atisnta. Georgia 3030?

Dear Mr. 0' hilly:

On April 27, 1979, a report was made under the provisions of 'EFR50.55(e) concerning potential overlonds of electrical systems which supoly offsite power fo- unit start-up as well as mergency Toads for both Units 1 and ? at North Anna. The potential overload involves the underground cibfes f-cr the reserve station service transformers to the 4'.~0 volt t-ansfer huses, the 419 volt circuit breakers which act as feeder breakers for the transfe* buses, and the 4150 volt transfer buses 0, E, and F.

A review of various stition conditions showed th3t when both Units 1 and 2 were using power from the reserve transformer source, the systems mentioned above would not be capable of continuously carrying the potential full load current. It was also determined that with unrestricted start-up loading of one unit the loading on the reserve source undergecund cables could exceed their continuous current carrying capability as calculated for a 40 . year cable life.

In order to alleviate the potential overload situation, we tre in the process of uograding the reserve oower supply for Units 1 and ?.

Specifically, an overhead bus is being built from the reserve transforners to the area of the north Nall of the turbine building. From this coint cables routed in cable trays will carry the power to the 4150 volt normal station buses for both units. The emergency buses (IH & J and 2H & ]) will be fed from the transfer buses, (D. E, & F) which will be fed by the existing underground cables from the reserve station transformers. Enclosed is a These revised one-line diagram showing the changes which m are undertaking.

changes will be reflected in the next amendment to the FSAR.

Detailed loading and voltsge profile studies have been oerformed in an effort to fully assess the capabilities of th upgraded systn. Various station continoencies were eunined including cne unit in start-up and the other unit trioped with loads transferred tutematically to the reserve source, snd one unit tripped under a loss of coolant accident condition with transfer These studies of loads to reseeve source while the other unit is in start-uo.

have shown all components involved in carrying power from effsite to the station loads are capable of carrying the worst-case postulated The concerns load forprofile of voltage one hour without any degradation of power feeds.

ind breskar f ault interrupting capability have required automatic shedding of certain non-essential normal loads during the conditions postulated above.

With this load shedding in effect, calculations have shown the voltage profile to be adequate, (3081 j S l[leggos290%y '

'4. James P. O'Reilly, Director 2 4 1s letter is our inte-in report of this situatinn. A final report will be submitted when the wrk is completei. However, we feel that this interim report ocovides all infomation required for your review of our acolication for an Operating License. If additional information is required for your revi n , please notify us.

Very trulv vours, h *,

Sam C. B Jr.

Senior Vice President Power Ststion Engineering and Construction cc: 'de . Ichn G. Davis, Acting Director Office of Inspection & Enforcement Mr. Harold R. Denton, Director Office of Huclear Reactor Reculation Enclosure

y k

t a 2 C -

5g 3 N 0 .

2 a.

c ,.

T 2p r/ ro s o o

I .

cr C N s. . ) Ee c i e tnA U s .B 2 s r i VR ri

i. <.

B uo ME Rs 4;,4 a., B A5 t r

. 2 e R wi y

) Es & od aPv 'a a3 1

t Ai E ut T s.

. t OA r-

,~ B~ TV"A)'

e '.-.

&, l

s t

i f

do S oi rA A

a 't /.a. , -

r Lv cC t a H 1 - A irT CsD E R

a. c, nE 0 k

s. - )a 3 I oR MA

s. 3W I

a. I .

p r /

S i.

c.

)

Em5w 2

)

2

>- I, l H

. f T l

2 u11 - j, l

T c

t.

s Cr u c.

) ) , f.

'm

/

~

"EI_ CB S 7

,s )

2 ,.

I

,s.

Q )S.2 ,

I .

y . 'C ys' n f.

/0 < .- - )

! I U 2- r 5 f c w B-1,. i)

c. "

/. 5l_

A t 2 2

a r'p' e 1

}9. '"l t;;.l l' l \lsi

, ,  !:  !.! .i J

,(! c. " "

S S. ,,Lm R

n

r. '

/

as ,. l i /

2 h. ..

A f- ((2 i.

2 'l S 5* e. c /

e.

< e.

u- T I S )

23 aa J.

c.)

s '

) 3 2

. z. r. N U

S X ,s. .

M w< .s. 4c. u '~: A o - .

2 3 l/

,. u ss '- a: 1 F.

., a

r' i

s)S'*

I A )5,b,. $l 1

H l;,

.ce s

c.

• j n

/.. J. e a, ,

a '*

3 g- to

/

. ~.' "' .c.u..

e. ,.

>*A - o

s.

• A r

n r .t D< (:: -

S- 3"f.h, a. i

,: f" f  :

)-

t E

/'C 5

nA wvc c

4 d, .

3 f-D

/

l 3l _

5 ,.

1, L

y t.

y 1

g

- )'

l C

"~

'f I s

) )  ; T l

T .

I S

/

t

!- {f )

N U S. s*C i

r I w

) t 2' e

vs 'f le A

q n x

)/n /;

E["

1' 2 L e j

/

s.

T*S. , <

_ I N S A, s

)

U 2, A

S.

I

!,' , :