ML18100B172

LER 94-009-00:on 940610,turbine/reactor Trip Occurred Due to Measured Ground Fault on Phase 1 Pt,Which Attributed to Component Failure.Defective Phase 1 PT & Blown PT Primary Fuse Were replaced.W/940629 Ltr

ML18100B172
Person / Time
Site:	Salem
Issue date:	06/29/1994
From:	Hagan J, Pastva M Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-94-009, LER-94-9, NUDOCS 9407070005
Download: ML18100B172 (6)

Text

• '

OPS~G e

Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038 Salem Generating Station June 29, 1994

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 94-009-00 This Licensee Event Report is being submitted pursuant to the requirements of Code of Federal Regulation 10CFR50.73(a) (2) (iv).

Issuance of this report is required within thirty (30) days of event discovery.

Sincerely yours, MJPJ:pc Distribution 9407070005 940629 PDR ADOCK 05000272 S PDR The po.ver is in your hands.

95-2189 REV 7-92

NRC FORM 366 .S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150*0104 (5-92) EXPIRES 5/31 /95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD LICENSEE EVENT REPORT (LER) COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB 7714), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF (See reverse for required number of digits/characters for each block) MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) PAGE (3)

Salem Generating Station - Unit 1 05000 272 1 OF OL..

TITLE (4) Turbine/Reactor Trip Due To Main Generator Ground Fault Protection Actuation With Reactor Power More Than/= 50%.

EVENT DATE (5) LEA NUMBER (6 REPORT NUMBER (7) OTHER FACILITIES INVOLVED 18\

FACILITY NAME DOCKET NUMBER SEQUENTIAL REVISION MONTH DAY YEAR YEAR MONTH DAY YEAR NUMBER NUMBER 05000 FACILITY NAME DOCKET NUMBER 06 10 94 94

-- 009 00 06 05000 29 94 OPERATING. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check one or more (11\

MODE (9) 1 20.402(b) 20.405(c) x 50.73(a)(2)(iv) 73.71 (b)

POWER 20.405 (a)(1 )(i) 50.36(c)(1) 50.73(a)(2)(v) 73.n(c) 20.405(a)(1)(ii) 50.36(c) (2) 50.73(a)(2)(vii) OTHER 20.405(a)(1)(iii) 50.73(a)(2)(i) 50. 73 (a) (2) (viii) (A) (Specify in Abstract below and in Text, NRG 20.405 (a)(1 )(iv) 50.73(a)(2)(ii) 50.73(a)(2)(viii)(B) .Form 3E/BA) 20.405(a)(1 )(v) 50.73(a) (2) (iii) 50.73(a)(2)(x)

LICENSEE CONTACT FOR THIS LEA 12)

NAME TELEPHONE NUMBER (Include Area Code)

M. J. Pastva. Jr. - LER Coordinator **-* (60Q) 139-lllli'l COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13\

.. REPORTABLE REPORTABLE CAUSE SYSTEM COMPONENT MANUFACTURER CAUSE SYSTEM COMPONENT MANUFACTURER 0 TO NPRDS. TONPRDS B

I YES EL XPT W120 (If yes, complete EXPECTED SUBMISSION DATE) y SUPPLEMENTAL REPORT EXPECTED 114\

x I NO EXPECTED SUBMISSION DATE (15)

MONTH DAY YEAR ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16)

On 6/.10/94, at 1434 hours0.0166 days <br />0.398 hours <br />0.00237 weeks <br />5.45637e-4 months <br />; a turbine/reactor trip occurred due to a turbine trip signal while above the P-9 reactor power interlock setpoint of >/= 50% reactor power. The turbine trip was initiated by a main generator ground fault protection relay, cv-.;..s, actuation.*** ..

Emergency operating procedures were entered and Main Steam was isolated to limit cooldown of the Reactor Coolant system (RCS)

Unit was stabilized in Mode 3. This event occurred due to an internal

. The ground fault on the primary high voltage winding of the phase 1 potential transformer feeding the main generator voltage regulator and relay circuits, which caused CV-8 to actuate. The PT and a blown PT primary fuse were replaced. Electrical tests were performed, which verified integrity of all main generator PTs and PT fuses. The PT insulators and cubicles were cleaned, as a preventive measure.

Additional investigation will be conducted to determine the failure mechanism of the phase 1 PT failure and appropriate action will be taken. Engineering is continuing to investigate RCS cooldown following trips* and potential corrective actions are being assessed.

NRC FORM 366 (5-92)

REQUIRED NUMBER OF DIGITS/CHARACTERS FOR EACH BLOCK BLOCK NUMBER OF TITLE NUMBER DIGITS/CHARACTERS 1 UP TO 46 FACILITY NAME 8 TOTAL 2 DOCKET NUMBER 3 IN ADDITION TO 05000 3 VARIES PAGE NUMBER 4 UP TO 76 TITLE 6 TOTAL 5 EVENT DATE 2 PER BLOCK

.. 7 TOTAL*

2 FOR YEAR 6 LER NUMBER

.3 FOR SEQUENTIAL NUMBER 2 FOR REVISION NUMBER 6TOTAL

7. REPORT DATE 2 PER BLOCK UP TO 18 - FACILITY NAME 8 *. OTHER FACILITIES INVOLVED 8 TOTAL - DOCKET NUMBER :

3 IN ADDITION TO 05000 9 1 .. OPERATING MODE 10 3 POWER LEVEL 1

11 REQUIREMENTS OF 10 CFR CHECK BOX THAT APPLIES UP TO 50 FOR NAME 12 LICENSEE CONTACT

. 14 FOR TELEPHONE CAUSE VARIES 2 FOR SYSTEM 13 4 FOR COMPONENT EACH COMPONENT FAILURE 4 FOR MANUFACTURER NPRDS VARIES 1

14 SUPPLEMENTAL REPORT EXPECTED CHECK BOX THAT APPLIES 6TOTAL 15 EXPECTED SUBMISSION DATE 2 PER BLOCK

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 94-009-00 2 of 4 PLANT AND SYSTEM IDENTIFICATION:

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

IDENTIFICATION OF OCCURRENCE:

Turbine/Reactor Trip Due To Main Generator Ground Fault Protection Actuation With Reactor Power >/= 50%

Event Date: 6/10/94 Report Date: 6/29/94 This report was initiated by Incident Report No.94-166.

CONDITIONS PRIOR TO OCCURRENCE:

Mode 1 Reactor Power 97% - Unit Load 1000 MWe Power reduction to 90%-was in progress to perform maintenance on 11 Heater Drain Pump motor {SJ/MO}.

DESCRIPTION OF OCCURRENCE:

On June 10, 1994, at 1434 hours0.0166 days <br />0.398 hours <br />0.00237 weeks <br />5.45637e-4 months <br />, a turbine/reactor trip {JC} occurred due to a turbine trip signal while above the P-9 reactor power ,,

interlock setpoint of >/= 50% reactor power. The turbine trip was initiated by a main generator ground fault protection relay CV-8 actuation. Emergency Operating Procedure (EOP)-TRIP-1, "Reactor Trip Or Safety Injection" and EOP-TRIP-2, "Reactor Trip Response" were entered and Main Steam was isolated to limit cooldown of the Reactor Coolant System (RCS). The Unit was stabilized in Mode 3 and Integrated Operating Procedure (IOP)-8 was entered.

At 1545 hours0.0179 days <br />0.429 hours <br />0.00255 weeks <br />5.878725e-4 months <br /> (same day) the NRC was notified of this event in accordance with 10CFR50.72(b) (2) (ii).

ANALYSIS OF OCCURRENCE:

The main generator ground protection relay CV-8 is fed by three main potential transformers (PTs) through three auxiliary PTs. The main PTs and the primaries of the auxiliary PTs are connected in Y-conf igurations and the secondaries of the auxiliary PTs are connected in an open delta configuration, with the CV-8 across the open delta.

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOC~ET NUMBER LER NUMBER PAGE Unit 1 5000272 94-009-00 3 of 4 ANALYSIS OF OCCURRENCE: (cont'd)

This event occurred when an internal ground fault occurred on the primary high voltage winding of the phase 1 PT {EL/XPT} feeding the main generator voltage regulator and relay circuits. This caused the PT primary fuse {EL/FU}, Westinghouse Model No. 677C452G04, to blow in order to clear the fault from the Generator 25 kilo-volt bus. In addition, it caused CV-8, which has a time delay, to pick up. CV-8 relay then timed out and picked up the "generator and main power transformer overall differential backup" multi~trip relay, which actuated to cause the main generat9r/turbine trip.

Equipment Performance As stated above, an internal ground fault occurred in the phase 1 PT, (Westinghouse Part No. EED2981). Additional investigation is required to determine the cause of the PT fault.

The time response and operation of CV-8 was found to be satisfactory.

Following the event reported in LER 272/94-007-00, two design change packages were implemented to limit post-trip cooldown. During this event, the plant response to cooldown was improved; however, MS167 closure was still required to limit post-trip cooldown.

APPARENT CAUSE OF OCCURRENCE:

This event is attributed to "Design, Manufacturing, Construction/Installation", as classified in Appendix B of NUREG-1022, due to a measured ground fault on the phase 1 PT, which is attributed to component failure. Additional testing is required to determine the exact cause of the ground fault.

PREVIOUS OCCURRENCES:

Review of documentation shows the cause of this event is an isolated occurrence.

SAFETY SIGNIFICANCE:

This event did not affect the health and safety of the public. It is reportable as an automatic Reactor Protection System (RPS) actuation in accordance with 10 CFR50.73(a) (2) (iv).

The RPS functioned as designed and the heat sink was maintained during this event. RCS cooldown requiring main steam line isolation has been experienced during other reactor trips (e.g., Unit 1 LER

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 94-009-00 4 of 4 SAFETY SIGNIFICANCE: (cont'd) 272/93-002-00, 272/94-005-00, 272/94-007-00, and Unit 2 LER 311/92-009-00). As described in the ANALYSES OF OCCURRENCE:

section design change packages have been implemented to limit post-trip cooldown and during this event the plant response to cooldown was improved.

CORRECTIVE ACTION:

The defective phase 1 PT and the blown PT primary fuse were replaced.

Electrical tests were performed, which verified integrity of all main generator PTs and PT fuses.

The PT insulators and cubicles were cleaned as a preventive measure.

Additional investigation will be conducted to determine the failure

.mechanism of the phase 1 PT failure and appropriate action will be taken.

Engineering is continuing to investigate RCS cooldown following trips and potential corrective actions are being assessed.

MJPJ:pc SORC Mtg.94-051