ML17266A098

LER 79-028/01T-0:on 790903,cable Fell Across Lines Into B S/U Transformer Causing Lockout on East Bus & de-energizing B S/U Transformer.Caused by Mechanically Binding Relay in auto-start Circuitry of Diesel Generator.Relay Was Replaced

ML17266A098
Person / Time
Site:	Saint Lucie
Issue date:	09/17/1979
From:	James D FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML17207A413	List: ML17207A412 ML17266A098
References
LER-79-028-01T, LER-79-28-1T, NUDOCS 7909270570
Download: ML17266A098 (2)

Text

NRC FOAM SSS U. S. NUCLEAR AECULATOAYCO&&MISSION

'P TTI LICENSEE EVcNT REPORT CONTAOI BLOCKI I I I IPLEASE PRINT OA TYPE ALL REOUIAEO INFORMATIONI IE I

LIS Q~tR F L S I I Q' poD1]

9 I

UCS!ISSS COOS Q., LIC~etNVM&th 15 2& L'CLVSS TYSS JO 51 ~T 5&

QE

",;'~iQE &0 SI 0

OOCKSTNUM&tR 0>> &S &9 SV SIIT OATS 14 15 ASSORT OATS SO

'10 EVENT OESCRIPTION *NO PROBABLE CONSECUENCES Mhsle sn the cold shutdown conltltlon during Herr>cane Oavtd, a cabl e fell

@ZAN across lines into the "B" S/U transformer, causing a .lockout on the

~O East Bus and de-energizing the UB" S/U transformer..The "B" A.C. electri-Cal SyStem WaS de-energiZed, and the UB" DieSel GeneratOr (DG) fai14ed tO

~at start. Following an electrical check-out, the "Bu DG was manually started-5 Adequate core cooling was maintained at all times. This is the fifth 2

~OB 3

5 9

occurrence of this type (See LERs 335-76-21, 76-44, 77-3 and 77-15).

9 SVSTSV LEEIS 2'I COOS 10 12 CAVSS COOS LA34 11 CAUst SU&COOS Luo 12 24 SSOUSNTIAL,

~io 12 1&

ccMnoNtNTcoot 21 IS OCCVIIRSNCS 29 29 SU&COOS M<0e 19 IISSORT 10 VALV 5USCOOS

'0L<JQ 21 t

htVISION ACTION SUTVRS ~ SSSCA SlauTOOvvN ATTACIaMSNT WRY SRLMS COMA COM SON SNT MANUSACTVIISAI TAKSN ACTION CN SLANT MSTIaOO NOURS +22 'SVSMITTSO SOAMbvt. SVSSLISR MARLrJR I EIQ I EIQ 0 ~ 0 LVJQ LeJO LAJQ LES34 3 f:

32 34 2& ~ 40 41 42 42 44 4Z CAUSE OESCAIPTION ANO CORRECTIVE ACTIONS Q?2 An investigation revealed that a rela in the auto-start circuitr of the "B" DG was mechanically binding. This relay was replaced: An operational test was then satisfactorily completed whereby the "B" S/U transformer

~i (which had been repaired and tested) was intentionally de-energized. The "Bu DG was observed to auto-star 90 2

~55 9

S AC IUTY STATVS

~GQEE ~00

'5 SOWER 0 Qel OTII th STATUS

.NA

~

~20 astTIIOO OS OISCOVthY

~AQEE 0 olscov thr OsschisTI0N erat'or Observation O42 9 9 10 I'2 12 SO T

ACTIVITY CON TSNT RSLSA5$ 0 0S RSLSAst AMOUNTOSACTIVITYQ~ LOCATION os ht LEASE Q>S B ~Z QSS ~ZQS& NA NA 9 9 10 Il 44 ~9 Sa SSRSONNSI. SXSOSVRSS

~OIF 0 QEE ~TQE NA So 2 9 11 12 12

~ SRSONNSL INIVRISS 3 9 9 II 12 SO'CSS Os OR OAMACZ TO SACIUTY Q&S

~j'Q, NR T S 9 10

~ VSLICITY NRC USE ONI.Y.

OSSCRIST:ON QS

~O 3

~Q

SSVSO NAAIIE OF PAEPAAER D. K. James PHONE:

(305) 552-3813.

092 pop

v

-REPORTABLE OCCURRENCE 335-79-28

=:1.ICENSEE EVENT REPORT

-'PAGE TWO

,~Additional Event Descri tion and Probable Conse uences kthile in the cold shutdown condition (Mode 5) during the passage of Hurricane

'gravid, a support cable for the tower crane in the Unit 2 construction area fell across lines into the "B" Start-up Transformer. A lockout

.occurred on the East Bus and the "B" Start-up Transformer was de-energized.

The "B" side of the electrical system de-energized with the exception of the

",B" .DC Bus which was carried by the "8" battery. The "B" Inverter failed =to wespond but the "D" Inverter remained in service. A blown fuse was discovered later in the "B" Inverter circuit. The "AB" A.C. Busses were lost

-as they were tied to the "B" side. The "AB" D.C. Bus was lost as it was tied to D.C. Bus, which is assumed to have de-energized as a result of the current transient produced by the event. The SUPS (including instrumentation, annunciation, lighting, comnunications Iexcept PAX and BELLj, NAWAS and Sequence ef Events Recorder) was also lost. At this time it was discovered that "B" Diesel Generator was not supplying loads (failed to start). Following a visual and electrical check-out of the "B" Diesel Generator, it was manually started.

Adequate core cooling was maintained and verified by starting the "4" LPSI pump

-and manually controlling Shutdown Cooling flow.

J Additional Cause Descri tion and Corrective Acti'on The "A" Diesel Generator was verified OPERABLE. All of the electrical busses and comp'onents lost during -event were re-energized. Since 4he reason fop the "B" Diesel Generator not starting automatically on undervoltage was not known, and the potential for a faulted bus or ground was suspected, a thorough check-out was conducted prior to manually. starting and loading the "B" Diesel Generator. Two days following the event, a plant staff review and investigation revealed that the K22 relay in the auto-start circuitry of the "B" Diesel Generator was mechanically binding.. This relay was replaced. Subsequently, an operational test was satisfactorily completed whereby the "B" Start-up Transformer (which was repaired and tested) was intentionally de-energized, and auto-start and loading of the "B" Diesel Generator was verified to occur,