05000318/LER-1980-023-03, /03L-0:on 800416,while 21 Diesel Generator Was Being Taken Off 24 4 Kv Bus Following Test,Two 15 Vdc Power Supplies Had No Output.Caused by Tripped Overvoltage Protection Modules

/03L-0:on 800416,while 21 Diesel Generator Was Being Taken Off 24 4 Kv Bus Following Test,Two 15 Vdc Power Supplies Had No Output.Caused by Tripped Overvoltage Protection Modules

ML19305E820
Person / Time
Site:	Calvert Cliffs
Issue date:	05/16/1980
From:	Davis S BALTIMORE GAS & ELECTRIC CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19305E814	List: 05000318/LER-1980-023, Forwards LER 80-023/03L-0
References
LER-80-023-03L, LER-80-23-3L, NUDOCS 8005200473
Download: ML19305E820 (2)

LER-1980-023, /03L-0:on 800416,while 21 Diesel Generator Was Being Taken Off 24 4 Kv Bus Following Test,Two 15 Vdc Power Supplies Had No Output.Caused by Tripped Overvoltage Protection Modules

Event date:
Report date:
3181980023R03 - NRC Website

text

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60 61 DOCK ET NUMBER 68 69 EVENT OATE 74 75 REPOR T OATE 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h I o 12 I l AT 1045 WHILE 21 DIESEL GENERATOR WAS BEING TAKEN 0FF 24 4 KV BUS FOLLOWING A I

Io Ia l l TEST, STEAM GENERATOR ISOLATION SIGNAL (SGIS) B BLOCK PERMITTED. SGIS B BLOCKED I

i o 14 i l AND LOCI SEQUENCER INITI ATED WENT INTO ALARM.

AN INVESTIGATION REVEALED THAT I

I o I s 1 l 'IVO 15 VDC POWER SUPPLIES HAD NO OUTPUT. THEY SUPPLY ESFAS LOGIC B CABINET I

I O ls 1 I SGIS/ RAS /CRS/CSAS, LOCI AND SHUTDOWN SE0VENCER FUNCTIONS.

(T.S. 3.3.2.1) 1 [O l 7 l l THE 15 VDC POWER SUPPLIES WERE RESET AND ESFAS LOGIC B CABINET WAS RETURNED I

ioIai i SERVICE AT 1340.

LER 79-31 (U-1) DESCRIBES A SIMILAR EVENT.

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33 34 JS 36 37 40 41 42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS li 101 l BOTH POWER SUPPLIES' OVERV0LTAGE PROTELTION MODULES HAD TRIPPED. REDUCING THFIR I

li t i l ! OUTPUTS TO NEAR 'O' VDC. THE ALARMS DESCRIBED AB0VE WERF RFCFIVFD COTNCTDFNT I

I li i 21 1 WITH THE OPENING OF N0. 21 EMERGENCY DIESEL GENERATOR OUTPUT BREAKER WHICH WAS i,i3i l CARRYING INSIGNIFICANT LOAD AT THE TIME. A PROCEDURE IS BEING DEVELOPED TO I

l ii141 l TROUBLESHOOT THE PROBLEM.

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50-318 EVENT DATE 04/16/80 REPORT DATE 05/16/80 ATTACHMENT CAUSE DESCRIPTION ArlD CORRECTIVE ACTIONS:

IMMEDI ATELY AFTER RESETTING THE +15 VDC POWER SUPPLIES, THE OVERV0LTAGE PROTECTION TRIP P0INTS WERE MEASURED AT +16.5 VDC. BOTH POWER SUPPLIES WERE FOUND TO BE OPERATING AT +15.1 VDC. AN OSCILLOSCOPE DISPLAYED N0 NOISE OR AC RIPPLE ON EITHER OUTPUT.

THERE IS NO APPARENT REASON FOR A TRANSIENT ON A 4 KV VITAL BUS TO INDUCE A TRANSIENT WITHIN THE ESFAS CIRCUITRY. THE ESFAS IS POWERED BY VITAL INVERTERS, WHICH ARE IN TURN POWERED FROM VITAL BATTERIES; THEREFORE, A PROCEDURE IS BEING DEVELOPED FOR TROUBLESHOOTING THE APPARENT CAUSE AND EFFECT.

SINCE SUBMITTAL OF LER 79-31 (U-1), MEASUREMENTS BY INDUCING 4 KV TRANSIENTS WHILE MONITORING VARIOUS POINTS WITHIN THE VITAL POWER TRAIN MADE ON THE VITAL AC POWER TRAINS IN UNIT 1 HAVE REVEALED N0 UNUSUAL DISTORTIONS NOR COMMON MODE NOISE PATTERNS. BENCH TESTS OF A REPRESENTATIVE ESFAS +15 VDC POWER SUPPLY REVEALED NO REGULATION PROBLEMS IN RESPONSE TO VARIATIONS IN SUPPLIED VOLTAGE OR FREQUENCY WITHIN ITS DESIGN SPECIFICATIONS.

FURTHER TESTING, EMPLOYING A NEWLY PROCURED TRANSIENT-RECORDING DEVICE IS EXPECTED TO BE COMPLETED BY JUNE 30, 1980.

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