ML18096B352

LER 93-006-00:on 930221,station Power Transformers 12 & 22 Deenergized Due to Tripping of Common 13 Kv Ring Bus Section 4 Breakers & 500 Kv Section 1 Breakers.Caused by Inadequate Communication.Caution Tags Hung on breakers.W/930323 Ltr

ML18096B352
Person / Time
Site:	Salem
Issue date:	03/23/1993
From:	Pastva M, Vondra C Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-93-006, LER-93-6, NUDOCS 9303260150
Download: ML18096B352 (6)

Text

{{#Wiki_filter:.e PSEG Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey. 08038 Salem Generating Station March 23, 1993 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 93-006-00 This Licensee Event Report is being submitted pursuant to the requirements of the Code of Federal Regulations 10CFR 50.73(a) (2) (i) (A). This report is required to be issued within thirty (30) days of event discovery. Sincerely yours,

                                                            .ri/ot?o-4-r
                                                         ~"c.       A Vondra -

• General Manager -

Salem Operations MJPJ:pc Distribution 260029 9303260150 930323 ~DR . ADOCK 05000272 PDR The rc~wcr is in \\!ur hand::;. 95-2189 REV 7-92

NRC FORM 366 (6-89) .. U.S. NUCLEAR REGULATORY COMMISSION re 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 (LERI COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REpORTS MANAGEMENT BRANCH (P-530). U.S. NUCLEAR REGULATORY COMMISSION. WASHINGTON. DC-20555. AND TO THE PAPERWORK REDUCTION PROJECT (3150-01041. OFFICE I OF MANAGEMENT AND BUDGET. WASHINGTON. DC 20503. FACILITY NAME' 111 DOCKET NUMBER 12) I PAGE 131 Salem Generating Station - Unit 1 o 15 I o Io I o 12 17 I' 21 , OF 0 15 TITLE (41 Tech Spec Required Shutdown Due to - Loss of One Off site Transmission Network. EVENT DATE 151 LER NUMBER 16) REPORT DATE (71 OTHER FACILITIES INVOLVED IBI MONTH DAY YEAR YEAR )\ SEQUENTIAL NUMBER tt REVISION NUMBER MONTH DAY YEAR FACILITY NAMES

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SUPPLEMENTAL REPORT EXPECTED (141 MONTH DAY YEAR EXPECTED

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DATE 115) I I I ABSTRACT (Lifnit to 1400 spaces, i.e., spproximsr8ty fiftetm singfe*spsce typewritten lines) 116) At 1332 hours on 2/21/93, the 2 .Station Power Transformer (SPT), 12 SPT, and 22 SPT deenergi*zed due to tripping (openJ the Units* common 13KV ring bus section 4 breakers and 500KV section 1 breakers. This resulted from closing the site 13KV gas turbine/generator (Unit 3) output breaker (3TG) onto the energized 13kV ring.bus, while Unit 3 was not running. Unit 1 was in MODE 2 and Unit 2 was at 100% while troubleshooting the breaker during testing,of Unit 3. Unit 1 was shutdown to MODE 3; as per Technical Specification (TS) 3_.4.1.1, due to loss of 13 and 14 Reactor Coolant Pumps. TS 3.8.1.1 wa.s entered for both units due to loss of an

       . independent off site AC power source to each unit

• The root cause of this event is personnel error. Due to inadequate communication between personnel involved with troubleshooting a problem with the breaker, it was closed. A contributing factor was insufficient knowledge of the breaker and the associated relay operation. Caution tags were hung on the 3TG breaker and its control switch. The importance of. communications and adhering to proper command and control has been reinforced. Lessons learned were discussed with station management and the involved personnel. The existing Lama co id at the 3TG breaker cubicle will be replaced with a different one to provide better information concerning racking-out the breaker. The 3TG breaker and the protective interlocks affected by operation of the breaker will be assessed for appropriate training and design enhancements.

NRC Form 36.6 (6-89)

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 93-006-00 2 of 5 PLANT AND SYSTEM IDENTIFICATION: Westinghouse - Pressurized Water Reactor Energy Industry Identification System (EIIS) codes are identified in the text as {xx} IDENTIFICATION OF OCCURRENCE: Technical Specifications Required Shutdown Due To Loss Of one Offsite

• Transmission Network Event Date: 2/21/93 Report Date: 3/23/93 This report was initiated by Incident Report No. 93-154.

CONDITIONS PRIOR TO OCCURRENCE: Unit 1: Mode 2 Reactor Power lE-8 amps Unit Load -o- MWe Unit 2 :. Mode 1 Reactor Power 106% Unit Load 1170 MWe DESCRIPTION OF OCCURRENCE: At 1332 hours on February 21, 1993, while troubleshooting the 13KV gas turbine/generator (Unit 3) generator output breaker 3TG, during testing of Unit 3, the 2 Station Power Transformer (SPT), 12 SPT, and 22 SPT deenergized. This resulted from tripping (open) the 13KV ring bus section 4 breakers (BS 3-4 and BS 4-5) and 500KV section 1 breakers (BS 1-5, BS 1-8, and BS 1-9), due to closing 3TG onto a live output bus. The loss of 2 SPT caused an automatic transfer of Unit 1 lA and lB 4kV Vital Buses to 11 SPT and Unit 2 2c 4kV Vital Bus to. 21 SPT. Unit 1 13 and 14 Reactor Coolant Pumps (RCPs) and 12B Circulating Water Pump tripped due to loss of 12 SPT, which

• deenergized lF and lG 4KV group buses. The bus design does not result in loss of Unit 2 RCPs since the Unit 2 Auxiliary Power Transformer was in service.

Per ACTION: of Unit 1 Technical Specification (TS) 3.4 .. 1.1 the unit was shutdown to MODE 3 due to loss of 13 and 14 Reactor Coolant Pumps. With the loss of 2 SPT "ACTION: "a" of Technical Specification (TS) 3.8.1.1 was entered for both units. At. 1430 hours (sam~ day) a one-hour notification to the Nuclear Regulatory Commission was made, in accordance with 10CFR 50.72(b) (1) (i) (A), to report the Unit 1 shutdown to MODE 3. TS 3.4.1.1 and required action states:

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem* Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 93-006-00 3 of 5 DESCRIPTION OF OCCURRENCE: (cont'd)

          "All reactor coolant loops shall be in operation.
        . APPLICABILITY:    MODES 1 AND 2*

ACTION:. with less than the above required reactor coolant loops in operation, be in at lease.HOT STANDBY within 1 hour." TS 3.8.1.1 and required action (both units) states:

          "As a minimum, the following A.C. electrical power sources shall be OPERABLE:

a. Two physically independent circuits between the offsite transmission network and the.onsite Class lE distribution system (vital bus system), and"

b. Three separate and independent diesel generators with:

1. Separate day tanks containing a minimum volume of 130 gallons of fuel, and

2. A common fuel storage system consisting of two storage tanks, each containing a minimum volume of 20,000 gallons of fuel, and two fuel transfer pumps."

ACTION: a of TS 3.8.1.1 states:

          "With either an offsitecircuit or diesel generator of the above required A.C. electrical pqwer sources inoperable, demonstrate the OPERABILITY of the remaining A.C. sources by performing Surveillance Requirements 4.8.1.1.1.a and 4.8.1.1.2.a2 within one hour and at least once per 8 hours thereafter; restore at least two offsite circuits and three diesel generators to OPERABLE status within 72 hours or be in at least HOT STANDBY within the next 6 hours and in COLD SHUTDOWN within the following 30 hours."

APPARENT CAUSE OF OCCURRENCE: The root cause of this event personnel error. Personnel troubleshooting the 3TG breaker did not adequately communicate thereby leading to breaker closure which caused the subsequent event. A contributing factor was insufficient knowledge of the breaker and relay operation on the part of the involved Nuclear Shift Supervisor (NSS), Nuclear Equipment Operator (NEO), Electrical Maintenance

  . Supervisor (EMS), and the Unit 3 System Engineer (SE).

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station 'DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 93-006-00 4 of 5 APPARENT CAUSE OF OCCURRENCE: (cont'd) The following sequence of events lead to the decision to close the breaker: At approximately 1230 hours on February 21, 1993, the NEO racked-in the Unit 3 generator output breaker, 3TG, ABB Type HK. During breaker rack-in, the SE did not hear the breaker charging springs charge. The NSS observed that the breaker springs were already charged and directed the NEO to rack-out the breaker. This was done to determine why the springs were charged before the breaker was racked-in. The NEO could not rack-out the breaker. The Electrical Maintenance Supervisor (EMS) inspected the breaker ~nd concluded that the breaker charging springs could be discharged to allow rack-out of the breaker by closing the breaker. With .the NSS present, the EMS directed the NEO to close the breaker. At 1332 hours (same day), the NEO closed the breaker initiating the event. ANALYSIS OF OCCURRENCE: This event did not affect the health and safety of the public. It is reportable per 10CFR 50.73(a) (2) (i)(A), due to the required shutdown of Unit 1 per TS 3.4.1.1, *following loss of 13 and 14 RCPs. This event was initiated by closure of the 3TG breaker without the Gas *Turbine Genera.tor running. This caused relays 8 6GBF (breaker failure multi-trip relay), 86GER (generator electric multi-trip relay), and 86Gl (generator regulator multi-trip relay) to actuate. Actuation of 86GBF relay caused the 3.TG breaker to trip open. Per design, the aforementioned breakers of 13KV bus section 4 and 5DOKV bus section 1 received open trip signais. Prior to this event Unit 1 was critical (MODE 2), with power level at lE-8 amps. 11 sPr was supplying power to lH and lE 4kV group buses and lC 4kV vital bus. 12 SPT was supplying power to lF and lG 4kV group buses and lA and lB 4kV vital buses. The deenergization of 13kV bus section 4 caused power to be lost to 12 and 22 SPTs. lF and lG group buses, which supply power to 13 and 14 RCPs, respectively, deenergized. This caused the 4kV load breakers to the RCPs as well as to 12 Circulating Water Pump trip open on bus undervoltage. In addition, the Unit 1 lA and lB 4kV vital buses, and the Unit 2 2C 4kV vital buses successfully transferred to their respective alternate SPT. The reduction in Reactor Coolant System (RCS) flow resulting from the loss *Of power to 13 and 14 RCPs did not challenge safety limits or limiting safety system setpoints. At reactor power levels below 10% rated thermal power, no protection circuit exists (in accordance with plant design) to open the Reactor Trip Breakers during reduced forced flow conditions. At power levels below 10%, the heat removal capability due to RCS natural circulation is sufficient to ensure adequate margins to Departure from Nucleate Boiling.

LICENSEE EVENT REPORT (LE~) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER .PAGE Unit 1 5000272 93-006-00 5 of 5 ANALYSIS OF OCCURRENCE: (cont'd) Loss of the SPT at main generator power levels greater than approximately 25% does not cause' loss of RCPs, since the 4kV buses are then normally supplied from the main generator via the Auxiliary Power Transformer. During this event, the Unit 2 systems important to safety performed as per design. The associated vital bus instrumentation remained energized and the vital bus undervoltage protection transfer sche.me performed successfully. CORRECTIVE ACTION: Four (4) caution tags were hung on the 3TG breaker and its control switch. a) One tag prohibits operation of the breaker in the TEST position without permission of the Unit 3 SE.* b) One tag cautions against racking-in the breaker with the breaker charging springs charged. c) Two tags, one on the breaker and the other on its control switch, prohibit closure of the breaker when the generator is not at normal speed, as it will actuate the breaker failure protection logic. Appropriate disciplinary action has been taken with the involved personnel. The importance of communications as set forth in the Work Standards Handbook is being reinforced with applicable station personnel. Lessons learned from this event were discussed with station management and involved personnel. The existing Lamacoid located at the 3TG breaker cubicle will be replaced with a new Lamacoid to provide better information to the operator concerning racking-out the breaker. The 3TG breaker and the protective interlocks affected by operation of the breaker will be assessed for appropriate training and design enhancements. 17/ot?~or tf'cc-eneral Manager - Salem Operations .MJPJ:pc SORC Mtg. 93-025}}