ML20095H878

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Special Rept:On 951120,2B DG Tripped on Loss of Excitation Due to Failure of R3 Potentiometer Associated W/Dg Voltage Regulator.Potentiometer Replaced & 2B DG Operated Successfully on 951122
ML20095H878
Person / Time
Site: LaSalle Constellation icon.png
Issue date: 12/18/1995
From: Ray D
COMMONWEALTH EDISON CO.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9512260210
Download: ML20095H878 (1)


Text

.

Commonwealth Ediwn Company .

,4 laSalle Generating Station

, 2001 North 21st Road Star +eille*, IL 61311 -9757 Tel M1F3574,761 December 18,1995 United States Nuclear Regulatory Commission Washington, D.C. 20555 Attention: Document Control Desk This special report is submitted in accordance with LaSalle Unit 2 Operating Licenses, Technical Specification 4.8.1.1.3 and 6.6.c regarding Unit 2 Diesel Generator (E22,2E22-S001).

On November 20,1995 with LaSalle Unit 2 at 100% power,the Unit 2 B (HPCS) Diesel Generator (DG) was being operated per LaSalle Operating Procedure LOS-DG-M3, "lB(2B) Diesel Generator Operability Test" After the engine was loaded to its full load, the Nuclear Station Operator (NSO) noticed large swings in the VAR loading of the engine. Before the operator could react to stabilize the VAR loading, the 2B DG tripped on Loss of Excitation. This failure was a valid failure in accordance with Regulatory Guide 1.108 and Technical Specification 4.8.1.1.3.

The cause of the 2B DG trip due to Loss of Excitation was the failure of the R3 potentiometer associated with the DG voltage regulator. System Operating Analysis Department (SOAD) and the DG System Engineer began troubleshooting the circuitry associated with the voltage regulator and found the resistance readings of the R3 potentiometer to be very erratic. The potentiometer was replaced and the 2B DG was operated successfully on November 22,1995.

If there are any questions or comments concerning this letter, please refer them to me at (815) 357-6761, extension 2212.

Res - ly, D.J. Ray Station Manager LaSalle County Station ec: H.J. Miller, Regional Administrator, Region III K.D. Ihnen, Acting Senior Resident Inspector, LaSalle l IDNS Resident inspector INPO - Records Center D. L. Farrar, Nuclear Regulatory Services Manager, NORS l Central file c r- j g

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