ML18096A980

LER 92-020-00:on 920817,generator-turbine Trip Occurred Due to Generator Differential & Loss of Field During Reinstallation of Voltage Adjuster.Caused by Design Deficiency.No Corrective Actions warranted.W/920910 Ltr

ML18096A980
Person / Time
Site:	Salem
Issue date:	09/10/1992
From:	Pollack M, Vondra C Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-92-020, LER-92-20, NUDOCS 9209210050
Download: ML18096A980 (4)

Text

e PS~G Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038 Salem Generating Station September 10, *1992 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Dear Sir:

SALEM GENERATING STATION LICENSE NO. DPR-70 DOCKET NO. 50-272 UNIT NO. 1 LICENSEE EVENT REPORT 92-020-00 This Licensee Event Report is being submitted pursuant to the requirements of the Code of Federal Regulations 10CFR 50.73(a) (2) (iv). This report is required to be issued within thirty (30) days of event discovery.

C. A Vondra Gen~ral Manager -

Salem Operations MJP:pc Distribution 180054

/r;JJ I 9209210050 920910

/)v I PDR ADOCK 05000272 95*2189 (10M) 12-89

. ~ . PDR

NRC FOFI~~ 366 U.S. NUCLEAR REGULATORY COMMISSION (6-89) APPROVED OMB NO. 3150-0104 EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS

• INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD LICENSEE EVENT REPORT (LER) . COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P*530l. U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555. AND TO THE PAPERWORK REDUCTION PROJECT (3150-01041. OFFICE OF MANAGEMENT AND BUDGET. WASHINGTON. DC 20503.

FACILITY NAME (11 DOCKET NUMBER (2_1 .. . I PAGE 13!

Salem denerating Station - Unit 1 O I 5 I O I O I O I? I ..., I ., 1 OF n h TITLE 141 Reactor Protection System signal actuation; Turbine Trip due to design.

EVENT DATE (5) LEA NUMBER 161 REPORT DATE (71 OTHER FACILITIES INVOLVED 1er MONTH DAY  ::::::::::;SEQUENTIAL 1::::::::: REVISION DAY YEAR FACILITY NAMES DOCKET NUMBERISI YEAR YEAR *:*:*:*:*:* NUMBER 1::::::::: NUMBER MONTH 01s1010101 I I THIS REPORT IS SUBMITTED PURSUANT TO TH_E RhQUIREMENTS OF 10 CFR §:(Chock one or more of th .. fa/lawing) (111 OPERATING MODE (9) 1 20.402(b) 20.405(cl

- l...X 50.73l*H2llivi 73.71lbl POWER LEVEL I Q ,__

20.4051*111 Hil ,__ *50.36(c)(1)

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LICENSEE CONTACT FOR THIS LEA (12)

NAME TELEPHONE NUMBER AREA CODE M.J. Pollack - LER Coordinator 61 O.19 3 I 3 19 I - 12 I O I 2 12 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (131 MANUFAC* REPORTABLE *:*: :*.* *:*: :*.**.*. MANUFAC*

CAUSE SYSTEM COMPONENT TUR ER TO NPRDS  :::;::::: *:* .*.* *.*. .*.: *.*..*.* CAUSE SYSTEM COMPONENT TUR ER I I I I I I I )) *:*-:*: :-:**:* .;.:;.: *:**:-:;.:

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I I I I I I I  :::;:::: I I I I I. I I *.*..*.*.*.**.*;*.*;:*:*:-:.;.:;*;*-:.;.:.;

SUPPLEMENTAL REPORT EXPECTED (141 MONTH DAY YEAR EXPECTED

_, YES (If. yes. complete EXPECTED SUBMISSION DATE!

ABSTRACT fL,(mir to 1400 spaces, i.e., approximately fifteBn single-space type_writtan lines) (16) h NO SUBMISSION DATE 1151 I I *I On 8/17/92, a generator-turbine trip occurred due to "Generator Differential and Loss of Field". The turbine stop valves closed per I design. At the time, the Unit was maintaining 21% reactor power with the turbine latched. A reactor trip directly occurs on a turbine trip only if reactor power is above 49%. Prior to the trip the automatic voltage regulator had been declared inoperable. The generator-turbine trip occurred during the reinstallation of the voltage adjuster. Station management had decided to delay putting the Unit on line to minimize a plant tiansient, if a problem developed with the voltage regulator repair. The root cause of this event is "Other"~ Investigation of this event revealed that Relay 5-86 (MG-6) initiated the generator-turbine trip. Energization of the relay causes "loss of field" which results in a generator-turbine trip. It is not considered possible for this relay to trip without excitation of the generator. Physical contact had to have been made during the voltage regulator adjuster installation. The 5~86 relay is neither covered nor encased to prevent inadv~rtent contact. It is also located very close to the voltage adjuster which was being replaced. The tight conditions and possible consequences were recognized by station management, so the unit was maintained off-line

• during this evolution. No corrective actions are warranted based on* the circµmstances surrounding this event; however, this event was discussed with those individuals involved.

NRC Form 366 (6-891

--,1 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION.

Salem* Generating station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272* 92-020-00 . 2 of 3 PLANT AND SYSTEM* IDENTIFICATION:

Westinghouse - Pressurized Water Reactor Energy Industry Identification System (EIIS) codes are identified in the text as {xx}

IDENTIFICATION OF OCCURRENCE:

React6r Protection System sign~l actuation; Turbine Trip due to design Event Date: 8/17/92 Report Date: 9/10/92 This. report was initiated by Incident Report No. 92-:-521.

CONDITIONS PRIOR TO OCCURRENCE:

Mode 1 Reactor Power 21% - Unit Load O MWe DESCRIPTION OF.OCCURRENCE:

On August 17, 1992, at 1737 hours0.0201 days <br />0.483 hours <br />0.00287 weeks <br />6.609285e-4 months <br />, a generator-turbine trip occurred due to "Generator Differential and Loss of Field". The turbine stop valves closed per design. At the time, the Unit was maintaining 21%

reactor power with the turbine latched. A reactor trip directly occurs on a turbine trip only if reactor power is above 49% (i.e.,

permissive P-9).

~rior to the turbine trip the automatic voltage regulator had been

• declared inoperable. Troubleshooting revealed that the voltage adjuster was mechanically binding. The generator-turbine trip occurred during the reinstallation of the voltage adjuster. station management had decided to delay putting the Unit on line to minimize a plant transient, if a problem developed with the voltage regulator repair.

A generator-turbine trip is a Reactor Prqtection System {RPS) {JC}

function. On August 17, 1992, at 1808 hours0.0209 days <br />0.502 hours <br />0.00299 weeks <br />6.87944e-4 months <br />, this event was reported to the Nuclear Regulatory Commission (NRC) in accordance with Code of Federal Regulations 10CFR 50.72{b) (2) (ii).

APPARENT CAUSE OF OCCURRENCE:

The root cause of this event is "Other" (per NUREG 1022, "Licensee

• Event Report Program") .

Investigation of this event, by System Engineering, revealed that Relay 5-86 (MG-G) initiated the generator-turbine trip. This relay is triggered by field forcing or over-excitation. Energization of

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 92-020.,...00 3 of 3

.APPARENT CAUSE OF OCCURRENCE: (cont'd) the.relay causes "loss of field" which results in a ge~erator-turbine trip. It is not considered possible for this relay to trip without excitation of the generator. Physical contact had to have been made during the voltage regulator adjuster installation.

The 5 ... a6 relay (as well as the other relays in the Voltage Regulator Cubicle) is -neither *covered nor encased to prevent inadvertent.

contact. It is.also located very close to the voltage adjuster which was being replaced. The tight conditions and possible consequences were recognized by station management, so the unit was maintained off-line during this evolution.

Installation of the voltage adjuster includes two bolts located behind

-the adjuster. During installation of these bolts the event occurred.

Tpough the technician does not recall contacting the relay, this is what has been determined to have occurred to cause this event.

Work within this cabinet is not normally conducted with the Unit in

.operation. The circumstances requiring replacement of the voltage adjuster warranted the risk. As explained above, the potential challenge to the plant and safety systems were minimized.

• ANALYSIS OF OCCURRENCE:

The "turbine trip" :function, when operating above P-9, part of the Reactor Protection System. It will cause a direct reactor trip when operating aeove P-9 thereby providing turbine protection and reducing

- the severity of the ensuing transient. No credit is taken in the

• accident analyses for this trip function.

This event did not affect the health or safety of the public*.. Since a turbine trip is an RPS function, this event is reportable to the NRC in accordance with Code of Federal Regulations 10CFR 50.73(a) (2) (iv).

CORRECTIVE ACTION:

No corrective actions are warranted based on the circumstances surrounding this event; however, .this event was discussed with those individuals involved. ~

• ih1Jtlfc~

Cbeneral Manager -

.Salem Operations MJP:pc SORC Mtg.92-101