ML20106B479

Special Rept:On 840928,power Circuit Breaker 22 Explosively Short Circuited,Causing Power Circuit Breaker 9 to Open, Isolating 230 Kv Overhead Line from Primary OL Power Source. Breaker Reclosed

ML20106B479
Person / Time
Site:	Oconee
Issue date:	10/03/1984
From:	Tucker H DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
NUDOCS 8410230220
Download: ML20106B479 (6)

Text

. .

~

DUKE POWER GOMPAhT P.O. BOX 33180 CHARLOTTE, N.C. 28242 HAL B. TUCKER Tzternown

.; .---,_ 84 0Cb&fr13; 144 * * * "

- Mr. James P.'0'Reilly,. Regional Administrator U. S. Nuclear Regulatory Commission Region II 101 Marietta' Street, NW, Suite 2900

- Atlanta Georgia 30323

Subject:

Oconee Nuclear. Station, Units 1, 2, and 3 Docket Nos. 50-269, -270, -287

Dear Mr. O'Reilly:

Please find attached a Special 5 day Report.concerning the isolation of

- the overhead power path from Keowee Hydroelectric Station (the primary emergency AC power source) to the Oconee station switchyard. Initial notification of this incident was made with the NRC Region II office on September 28, 1984. This report is submitted pursuant to Oconee Nuclear Station Technical Specification 3.7.9 and describes an incident which is considered to be of no significance with respect to the health and safety of the public.

Very truly yourc, I

i s

D fLLc wy o

Hel B. Tucker RFH: sib Attachment ec: Document Control Desk Ms. Helen Nicolaras U. S. Nuclear Regulatory Commission Office of Nuclear Deactor Regulation Washington, D. C. 20555 U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Mr. J. C. Bryant NRC Resident Inspector Oconee Nuclear Station INPO Records Center Suite 1500 1100 Circle 75 Parkway Atlanta, Georgia 30339 OFFICIAL CUP 8410230220 841003 i l e/ 6 g b i PDR ADOCK 05000269 ~  !

s S PDR

{  ;

~

f[ ]

Mr.'Jame] P. O'Reilly, Regitnal Adminictritcr

October ~3, 1984 Page Two bec: P..M. Abraham

~R. T. Bond R. J. Brackett K. S. Canady L. M. Coggins J. W.'Cox R. C. Futrell E. M. Geddie S. G. Godwin P. F. Guill S. B. Hager M. A. Haghi W. A. Haller

,G. W. Hallman T. P. Harrall S. A. Holland C. C. Jennings

-H. R. Lowery T. C. Matthews M. D. McIntosh-T. E. Mooney R. G. Morgan M. E. Pacetti R. P._ Rogers N. A. Rutherford.

A. L. Snow R. V. Straub (B&W)

E. L. Thomas G. E. Vaughn W.' Washington Group. File: OS-801.02 Group File: OS-815.04 l

l l-i

p. ,

v Duke Power Company Oconee Nuclear Station Special Report.

230KV Overhead Line Between Keowee and Oconee Isolated Due to Opening.cf PCB-9 Description of-Occurrence:

On September 28, 1984 at 1321 hours0.0153 days <br />0.367 hours <br />0.00218 weeks <br />5.026405e-4 months <br />, Power Circuit Breaker (PCB) 22 explosively short-circuited while being put back into service following the repair of an SF6 gas leak. The short circuit. tripped PCB-22.which caused a red bus differential lockout and opened ?CBs 7, 8, 9, 10, 13, 16 19, 23, 26, 28, and 31.- The unexpected opening of PCB-9 isolated the 230KV overhead line from the Keowee_ Hydroelectric Station-(the primary emergency AC power source) resulting in operation contrary to an applicable technical specification: The technical specification states that when one Keowee unitais unavailable for longer than 72

' hours, then the remaining unit shall be available to the 230KV overhead transmission circuit. Keowee Unit 2 was unavailable due to a' scheduled maintenance outage. Operations personnel determined that the safest manner in which to resume operation under the technical specification was to close PCB-9; this was done after> confirmation that the red bus differential lockout indeed had been caused by the PCB-22 failure. The red bus differential lockout was reset at 1427 hours0.0165 days <br />0.396 hours <br />0.00236 weeks <br />5.429735e-4 months <br /> and PCBs 7, 8, 10, 13, 16, 19, 26,' 28, and 31 were reclosed. PCB-22 was isolated so that its inspection and repair could begin. PCB-23 was reclosed at 1521 hours0.0176 days <br />0.423 hours <br />0.00251 weeks <br />5.787405e-4 months <br /> following an inspection for possible damage due to its proximity to the PCB-22 explosion.

Cause of Occurrence:

An SF6 gas leak had been identified prior to September 25, 1984 when PCB-22 was isolated for maintenance. The leak was found in a cracted weld in the lower part of the third (3rd) phase support section. The weld was repaired but a smaller leak still existed on September 28, when PCB-22 was being put back into service. The leak was small enough that PCB-22 was to be put into service during the period of September 29th and 30th and then removed from service October 1st for the smaller gas leak to be repaired.

Figure 1 is an electrical schematic diagram of the Oconee switching station which shows the relative positions of the various breakers.

A drawing of power circuit breaker PCB-22 is included as Figure 2. The short circuit occurred inside the third (3rd) phase section of PCB-22.

The_ porcelain insulator on the west side of this section was shattered by the short circuit. The cause of the short circuit had not been

! . determined as of October 3rd.

i l

l 1

4:

Analysis of Occurrence:

The explosion which occurred when PCB-22 short circuited caused no injuries to station personnel and no apparent damage to equipment other than PCB-22.

The fact that the station operated in"a manner which was inconsistent with the applicable technical specification, for an interval of approximately 17 minutes, did not result in an. unsafe condition. Keowee Hydro Unit I was available via the 13.8KV underground feeder circuit, and the dedicated combustion-turbine driven generators.at the Lee Steam Station were avail-able as a secondary emergency power source. Therefore the' health and safety,of the public were not affected by this incident.

Corrective Action:

Following an on-the-spot safety. evaluation by Operations personnel, PCB-9 was reclosed, thus ensuring that station operation would proceed in accordance with the technical specification. The Keowee Unit 2.

maintenance outage was completed earlier than scheduled.and a routine maintenance step requires Unit 1 to be temporarily removed from service so that both units can be returned to-service. Return of the units is expected by October 5, 1984, at which time the affected technical specifi-cation will no longer apply. Repair work is proceeding on PCB-22. While the Keowee units are out of service, tests using input signals are being conducted to determine why PCBs 8 and 9 opened on the red bus differential lockout.

Y

-w -- -- - - - . - , - - - . -, -e.--

m' (W.C'ville) (Castral) (Cextral)

'sa O'** 8'288'"

' I'** L l'I-~~ [

es.wo. 1 ' <

'v s

i e

a, s  % + .- - - 2M N 32 n.a n . ,

o

.' . i .i i

~

\ \ \ \ 6 \ 22 ,

7

'T

_ E. . -

2 C.. .

-I POWER C CUITI k __, I .I s.nn.* 9=

e n > .a P

- BREAKER ARRANG.a ,v

,e

.s ..... -

i i' -

is.: x, i

v.4.re. rar. i g

l - .

>-1 D-

. g .m

=m. ., a m . .

g j

l ,

f "' "i l Lu _ si la m _

T . T "' -

j C.1(-p q 7,7 T -= @ ,.Js _ sim 7 -> @.T 7 n;. y .

su ~~ ~ ~

e

! v I - I - _ _. v l I -

ITs 27A 275 3fA 373 , ,

lA

, , , e ELECTRICAL f

n. ~,.., ua.

i l. .

STSY Sn. 1 .

I 230-525 RV $witeht.g st.tl.a i

i' 1

/

I sur = 2 l '

1 .

1 i

e, OC-ELE-IF9al ).t.s19-20-76 AEF:FSARITl'33-2 lREV.O HFS2 31y33

! 1 - . MFBI

, nr.wwe t 11418 hPF

! ITC .. ITD ITE 2TC ITD ITE STC 31'S 3TE

IGUR t2.

~

I 15-9. 8.3 -1 I I POWER CIRCUIT BREAKERS PAGE 4 :

',s t, '

ENTRANCE 1

1/ BUSHING

.3FC  !

/ ,!/ TRANSF M #8  !

(\,#9M%

OPERATING MECHANISM i

i

(

QM -

j, '

g MANHOI.E

%-JL I --.

DOOR

)

vtcto LoomN(7 540Df.

x COMMON BASE FIGURE i BREAKER OUTLINE Vfst.O /oc/c(q

~

W{

(

I A

' ' ' '~

ENTRANCE -

8USHING l  ! i CENTER  % -

SUPPORT /- -

INSUI.ATOR SHIEl.DEO

[ ..

MULTI-BREAK INTERRUPTERS STATIONAR  ! HIGH PRESSURE CONTACT < s ( '

RESERVOjRS NOZZLES '= .

_k _

~

[

% PORCELAIN o / ,,

INSULATORS L%Y-"DLiiQs P0R.CGLhlA a. $ - AUXILIART, s ,-.w -

=r, l lN5VLM 1_ - ~ ~

. _1 $_ ,'] HIGH PRES 5URE L BLWwn '70 GAS RESERVOIR

! f/EC65 FIGURE 2 SINGLE POLE CROS5 SECTION .-

l_ _ $$W UONIbl$ AIORTO' - -- - ---------.