05000304/LER-1986-010-04, :on 860219,during Performance of Diesel Generator Loading Test,Generator Tripped.Caused by Partially Closed Fuel Oil Day Tank Suppl Valve.On 860220,second Generator Tripped Due to Failed Relay.Relay Replaced

:on 860219,during Performance of Diesel Generator Loading Test,Generator Tripped.Caused by Partially Closed Fuel Oil Day Tank Suppl Valve.On 860220,second Generator Tripped Due to Failed Relay.Relay Replaced

ML20141H963
Person / Time
Site:	Zion File:ZionSolutions icon.png
Issue date:	04/22/1986
From:	Sassaman S COMMONWEALTH EDISON CO.
To:
Shared Package
ML20141H957	List: 05000304/LER-1986-010-04, :on 860219,during Performance of Diesel Generator Loading Test,Generator Tripped.Caused by Partially Closed Fuel Oil Day Tank Suppl Valve.On 860220,second Generator Tripped Due to Failed Relay.Relay Replaced
References
LER-86-010-04, LER-86-10-4, NUDOCS 8604250252
Download: ML20141H963 (4)

LER-1986-010, on 860219,during Performance of Diesel Generator Loading Test,Generator Tripped.Caused by Partially Closed Fuel Oil Day Tank Suppl Valve.On 860220,second Generator Tripped Due to Failed Relay.Relay Replaced

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(x)
3041986010R04 - NRC Website

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LICENSEE EVENI REPORI (LER) l Facility Name (1)

".)ocket Nurter (2)

Page (3)

Zion. Unit 2 Ol $1 01 01 01 31 01 4 Ilof!0l3 Failure of 0 diesel generator while 2A diesel generator was inoperable Event Date (5)

LER Nurter (6)

Report Date (1)

Other Facilities Involved (8) j/jj Sequential /j/j/ Revision Month Day Year Facility Names Docket Nunber(s)

Month Day Year Year

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Number

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Nunber 01 51 01 01 01 I I 012 119 816 816

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, X_ 50.36(c)(2) 50.13(a)(2)(viii)(A) in Abstract below

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20.405(a)(1)(iv) 50.13(a)(2)(ii) 50.13(a)(2)(viii)(8) and in Text)

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Steven W. Sassaman. Technical Staff Engineer. Extension 320 3l1l2 11 41 61.-l 21 Ol 81 COMPLETE ONE LINE FOR EACH COMPON FAILURE DESCRIBED IN THIS REPORT (13)

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1. • I A851RACI (Limit to 1400 spaces, i.e, approximately fif teen sir.gle-space typewritten lines) (16)

On 2/19/86, 2A diesel generator was started for a perfonnance test (PI-11 Diesel Generator Loading Test). Two minutes atter starting, at 2030, 2A diesel tripped oft due to a partially closed fuel oil day tank supply valve. O diesel was started for a PI-11 test in response to 2A diesel inoperability. At 2117 0 dissel came up to rated speed, then tripped. A generating station emergency plan event was declared until 2A diesel had successfully conpleted PI-11 at 0030, 2/20/86. On 0 diesel, investigation found that a relay in thz starting circuit failed to remain sealed in with one of its own contacts after the initial starting signal was given. The contact was oft center and intermittently failed. Before the relay problem was found, a subsequent failure occurred at 2135 on 2/20/86 during a PI-11 test.

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Safeguards starting was available through relays that would have bypassed the faulty relay. The relay

as replaced and 0 diesel was successfully tested and back in service by 1040, 2/23/86.

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8 PDR 02140

LICENSEF EVENT REPORT (LER) TEXT CONTINUATION FACILiiY NAME (1)

DOCKET NUMBER (2)

LER NUMBER (6)

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Zion. Unit 2 0 l 5 1 0 1 0 1 0 l 310 14 816 0l110 010 012 0F 013_

1EX1 Energy industry identification System (E!!S) codes are identified in the text as [xx]

A.

PLAhi CONDITIONS PRIDH TO EVEN1:

Unit 1: MODE I - Power Operatica~ RX Pcwer - 99%

Unit 2: MODE I - Power Operation RX Power - 98%

B.

DESCRIPTION OF EVENT

On 2/19/86, 2A diesel ger.erator was started for a perforTnance test (PI-il Diesel Generator Loading Test).

lwo minutes cfter starting, at 2030, 2A diesel tripped oft due to a partially closed fuel oil day tank supply valve. O diesel was started for a PT-11 test in response to 2A diesel inoperability. At 2111 0 diesel came up to rated speed, then tripped. A generating station emergency plan (GSEP) unusual event was declared and th? NRC was. notified at 2143. The G5EP event remained in effect until 2A diesel had successfully completed PT-Il at 0030, 2/20/86. The tailure of diesel generator 2A and its resolution are described in detail in Zion Deviation Report 2-86-031.

At Olli on 2/20/86, a Pi-11 test was successfully perfortned on 0 diesel generator. At this point however, the cause of the original 0 diesel generator failurt was unknown. Therefore, at 1045, 0 diesel generator was taktn out of servic? for troubleshooting. After approximately 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> of investigation, the engineer felt that he had located the problem. Following several successful maintenance starts, PI-11 test was attempted at 2135 on 2/20/85_ During this test, O diesel generator again came up to rated speed and tripped off. At this point, another investigation of the entire starting system was perforined. The source of the trouble was found on 2/22/86, and 0 diesel generator was given a successful PI-11 on 2/23/86 and placed back in service.

The engine is a Cooper Bessemer KSV-16-I diesel that runs an cmcrgency 4 megawatt generator.

C.

CAUSE OF EVENT

A f aulty relay, in the Cooper Besser En-tronic Control system, caused the O diesel engine to trip soon after starting. The relay tailed intertnittently, thus trouble shooting involved intensive investigation of th2 entire starting system, the second f ailure to start, which occurred on February 20th at 213$ during a subsequent PI-Il test, led to discovery of the relay problem. A movable contact was found off center thus not always providing the continuity needed to keep the relay energized after the initial start signal was given.

Without this self sealing action, the engine would trip itself and indicate a nortnal engine shutdown on the annunciator.

D.

SAFETY ANALYSIS

After each failure of 0 diesel generator, all engineered safety feature (LSF) buses were verified to hav?

nortnal power. Diesels IA and 18 for Unit I and diesel 28 for Unit 2 were verified operable by PI-Il testing.

Dissel 2A was verified operable by PI-11 testing at 0030 on 2/20/86 thus ending the GSEP condition.

1he troubleshooting group discovered that at the time of its PI-Il failures, O diesel would still have started for a loss of power or safeguards actuation condition, because an independent se'. of relays would have byptssed the faulty relay. 1herefore, O diesel was cnly inoperable for manual starts. Since the bypass relays would have started 0 diesel on a safeguards actuation, and since 2A diesel was back in service while O diesel was out of service for trouble: hooting, there were always at least 2 diesel generators available to provide emergency power if needed.

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LICENSEE EVENT REPORT (LER) TEXT CONTINUATION

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Zion. Unit 2 0 l 5 l 0 l 0 l 0 l 310 14 816 0l110 010 013 0F 013 TEXT Energy Industry identification System (Ells) codes are identified in the text as [xx]

E.

CORRECTIVE ACTIONS

The faulty relay was replaced with a new one. Additional starts were pertonned using a brush recorder to monitor key portions of the starting circuits. No other problems were indicated. The diesel was given a successful PT-11 test on February 23rd and placed back in service.

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PREVIOUS OCCURRENCES

A search of the NPRDS conputer files did not indicate trouble of this kind in the Cooper Bessemer En-tronic control system.

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COMPONENT FAILURE DATA

MANUFACTURER NOMENCLATURE N00EL NUMBER MG PART NUMBER Kurman Instrument 3 Pole, Double throw Kunnan Instrument Cooper Bessemer Corp. (inade for 11 pin plug relay, Corp. No.: 2603C Co. No.: 2-04E-150-001 Cooper Bessemer) 1 3/8' X 1 3/8" X 2 1/4",

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