ML20086K990

AO 74-3:on 740125,electrical Fault Found in Voltage Regulator of Emergency Diesel Generator E-4.Caused by Cable Chase Below Generator Voltage Regulator Filled W/Water. Leaking Condensate Return Unit Removed from Svc

ML20086K990
Person / Time
Site:	Peach Bottom
Issue date:	02/04/1974
From:	Cooney M PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20086K994	List: ML20086K990 ML20086L000
References
AO-74-3, NUDOCS 8402070106
Download: ML20086K990 (3)

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PHILADELPHIA EL$CTRIC COMPANY ,,

2301 MARKET STREET '2 g$74 '" O .-- C-(..enO3 [J PHILADELPHI A. PA.19101 , o 12151841 4o00 / February 4, 1974 Mr. A. Giambusso Deputy Director of Reactor Projects United States Atomic Energy Commission , Directorate of Licensing Washington, D. C. 20545

Subject:

Abnormal Occurrence The following occurrence was reported by telephone to Mr. R. A. Feil, A.E.C. Region I Regulatory Operations Office on January 25, 1974. Wri tten noti fication was made to Mr. J. P. O'Reilly, A.E.C. Region i Regulatory Operations Office on January 25, 1974. In accordance with Section 6 7 2.a of the Technical Specifications, Appendix A of DPR-44 for Unit 2 Peach Bottom Atomic Power Station, the following re-port is being submitted to the Directorate of Licensing as an Abnormal Occurrence.

Reference:

License Number DPR-44, Amendment Number 1, Appendix A revised October, 1973 Technical Specification 3 9.A.2 Report No. : 50-277-74-3 Report Date: 2/4/74 Occurrence Date: 1/25/74 Identification of Occurrence: ! Electrical fault in the voltage regulator of the E-4 Emergency l Diesel Generator. Fault occurred during routine surveillance testing. Conditions Prior to Occurrence: Reactor critical in source range and vented at 160 F coolant temperature. , i i h2hp0 ' 01 COPY SENT REGION - v -- _ _ _ ._ ____

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Designation of Apparent Cause of Occurrence: l The cable chase below the generator voltage regulator had filled with water. The failed current transformers are located in the bottom of the regulator cubicle and were the first piece of electrical apparatus to come in contact with the water (the current transforcers were not submerged, but were in the very humid atmosphere just above the water level). Analysis of Occurrence: The diesel generator building steam heat condensate return unit is located in the E-4 Diesel Bay approximately 10 feet from the voltage regulator and control panel and six feet from a floor drain. Packing leakage from the condensate return unit pumps ran onto the floor, and due to local irregularities in the floor slab, a portion of the water ran over to the voltage regulator and control panel in-stead of the floor drain. Af ter some period of time, this leakage had completely filled the cable chase beneath the voltage regulator. It was at this time that the current transformer failure occurred. l The failure of this diesel generator would not have pre-vented operation of safe guard equipment because of the availability of the remaining three diesel generators. 1 Corrective Action: The leaking condensate return unit was removed from service and the cable chase pumped out. The cables, terminations, and supports were thoroughly dried with quartz heaters. The voltage regulator was functionally tested and the generator armature, field, and cables out to the circuit breakers were electrically tested. The insulating boards supporting the current transformers indicated various amounts of electrical tracking. One section of board was replaced, the re-mainder was satisfactorily cIcaned. All three phase current trans-forners were replaced. All primary and secondary connections will be proven before the E-4 Diesel Generator is returned to service (estimated 2/6/74). The heating system condensate return pumps have been rebuilt and repacked. To prevent pump leakage from entering the cable chase in the future, the following steps are being taken before returning to power operation:

1. The condensate return will be enclosed by a metal barrier which will be piped directly to the floor drain.

2. Visual inspection of the cable chase will be added to the operator's routine surveillance of the equipment

    .                        in the Diesel Generator Building.

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Failure Data: No previous occurrence. Very truly yours, ty

                                            /M./T (<

n u.uf Cooney Ass't Gen't Superintendent Generation Division cc: Mr. J. P. O'Reilly Director, Region 1 United States Atomic Energy Commission 631 Park Avenue King of Prussia, PA 19406 l 1 l}}