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 J, VONDRA C A 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 Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038 Salem Generating Station 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 September 10, *1992 This Licensee Event Report is being submitted pursuant to the requirements of the Code of Federal Regulations lOCFR 50.73(a) (2) (iv). This report is required to be issued within thirty (30) days of event discovery.

MJP:pc Distribution 180054 9209210050 920910 PDR ADOCK 05000272 . . PDR C. A Vondra Manager -Salem Operations

/r;JJ I /)v I 95*2189 (10M) 12-89 NRC 366 (6-89) U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 3150-0104 EXPIRES: 4/30/92 LICENSEE EVENT REPORT (LER) . ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS *INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD 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 Salem denerating Station -Unit 1 'DOCKET NUMBER (2_1 .. . I PAGE 13! 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 YEAR YEAR *:*:*:*:*:*

NUMBER 1:::::::::

NUMBER MONTH DAY YEAR FACILITY NAMES DOCKET NUMBERISI 01s1010101 I I OPERATING MODE (9) THIS REPORT IS SUBMITTED PURSUANT TO TH_E RhQUIREMENTS OF 10 CFR §:(Chock one or more of th .. fa/lawing)

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--20.4051*111 lM 50.73(ol(2lliiil 50,73(ol(2llxl 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 :*:*:*:* .;.;:.* . . *.* *.; .. ;.: CAUSE SYSTEM COMPONENT MANUFAC* REPORTABLE

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SUPPLEMENTAL REPORT EXPECTED (141 MONTH DAY YEAR EXPECTED SUBMISSION DATE 1151 _ , YES (If. yes. complete EXPECTED SUBMISSION DATE! h NO I I ABSTRACT fL,(mir to 1400 spaces, i.e., approximately fifteBn single-space type_writtan lines) (16) On 8/17/92, 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%. 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 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 relay is neither covered nor encased to prevent 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 *I I LICENSEE EVENT REPORT (LER) TEXT CONTINUATION.

Salem* Generating station Unit 1 DOCKET NUMBER 5000272* PLANT AND SYSTEM* IDENTIFICATION:

Westinghouse

-Pressurized Water Reactor LER NUMBER 92-020-00 . PAGE 2 of 3 Energy Industry Identification System (EIIS) codes are identified in the text as {xx} IDENTIFICATION OF OCCURRENCE:

React6r Protection System 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).

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 lOCFR 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 --, ._ 1 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station Unit 1 DOCKET NUMBER 5000272 .APPARENT CAUSE OF OCCURRENCE: (cont'd) LER NUMBER 92-020.,...00 PAGE 3 of 3 the.relay causes "loss of field" which results in a 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 lOCFR 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. MJP:pc SORC Mtg.92-101 Cbeneral Manager -. . Salem Operations