ML20127J954
| ML20127J954 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 04/30/1985 |
| From: | Keiser H PENNSYLVANIA POWER & LIGHT CO. |
| To: | Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| PLAS-070, PLAS-70, NUDOCS 8505210628 | |
| Download: ML20127J954 (2) | |
Text
.
M.,
PPat Pennsylv nin Pow r & Light Comp:ny Two North Ninth Street
- Allentown, PA 18101
- 215/ 770-5151 April 30, 1985
-Dr. Th mas E. Murley Regional Administrator, Region I U.S. Nuclear Regulatory Ccanission 631 Park' Avenue King of Prussia, PA 19406 SUSQUEHANNA STEAM ELECTRIC STATION SPECIAL REPORT - NON-VALID DIESEL FAILURE ER 100450 FILE 841-23 PIAS-070 Docket No.
50-387 License NO. NPF-14
Dear Dr. Murley:
his special report documents the "C" Diesel Generator Non-Valid Failure as required by Regulatory Guide 1.108, Section C.3.b, and Technical Specification 4.8.1.1.3.
Regulatory Guide 1.108, Section C.3.b, requires reporting all diesel generator the "C" Diesel failures, valid or invalid. At 1925 on March 29, 1985, _
Generator autmatically started, but then tripped on overspeed. Investigation revealed a broken lug on the positive terminal at 125 VDC Distribution Panel 1D634 breaker.05 which supplies power to the "C" Diesel Generator primary start circuit and the generator voltage regulator. Modification work was in progress in the 125 VDC Distribution Panel when the event occurred.
De-energizing the primary start circuit caused the mergency start relay to drop out. This relay has contacts in the secondary start circuit which caused the diesel to start. Since power was interrupted to the generator voltage regulator, the regulator was in a shutdown state, causing the generator output to be zero. The "C" Diesel Generator accelerated much faster than during a normal start due to starting air being injected into the cylinders, up to 660 rpn, the nechanical overspeed trip setpoint. he starting air on a normal start shuts down at 280 rpm as sensed in the primary start circuit. We secondary control circuit starting air shut-off s'gnal also originates in the primary start circuit, which was de-energized.
The diesel generator overspeed was caused by a cmbination of the following conditions: We speed input for the electronic governor is sensed fr m the output of a potential transformer located at the generator output. Since the.
generator output was zero volts, the electronic governor was not operational.
Starting air continuously being injected into the cylinders created higher engine efficiency, resulting in a faster than normal acceleration. The mechanical governor response was not adequate to prevent the overspeed. Wis start was initiated by a loss of control power to the primary start circuit, which is not a valid start signal. There were no adverse effects to the 8505210628 850430 PDR ADOCK 05000387 l
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diesel generator'due to this start and overspeed-trip. N broken terminal
- lug was treplaced and the diesel was successfully restarted at 2040 on March -
29, 1985.-
~ The Diesel Generator. Start Iog indicated there is one'- (1) ~ diesel: failure in
- the last one hundred (100) starts. h diesels are on a test. interval of.
every thirty-one, (31) days, per Regulatory Guide 1.108, Section C.2.d.
M H..-Keiser Superintendent of Plant-Susquehanna NG/pjg cc: Mr. R.H. Jacobs
- Senior' Resident Inspector U.S. Nuclear Regulatory Ccanission
- P.O. Box 52
- Shickshinny, PA 18655 U.S. Nuclear Regulatory Ccanission Document Control Desk Washington, DC-20555 l
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