ML20209G617
| ML20209G617 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 11/26/1986 |
| From: | Crimmins T PENNSYLVANIA POWER & LIGHT CO. |
| To: | Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| PLAS-215, NUDOCS 8702050406 | |
| Download: ML20209G617 (3) | |
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Q Pennsylvania Power & Light Company Susquehanna Steam Electric Station P.O. Box 467
- Berwick, PA 18603
- 717 / 542-2181 November 26, 1986 Dr. Thcmas E. Murley Regional Administrator, Region I U.S. Nuclear Regulatory Ccmnission 631 Park Avenue King of Prussia, PA 19406 SUSQUEHANNA STEAM ELECTRIC STATION SPECIAL REPORT
'A' DIESEL GENERA'IOR NON-VALID FAILURE FILE R41-2 PLAS-215 Docket No.
50-387 License No. NPF-14
Dear Dr. Murley:
All Diesel Generator Unit failures, valid or invalid, are to be reported as required by Regulatory Guide 1.108, Section C.3.b, and Technical Specification 4.8.1.1.3.
At 0921 hours0.0107 days <br />0.256 hours <br />0.00152 weeks <br />3.504405e-4 months <br /> on October 30, 1986, the 'A' Diesel Generator (D/G) was started in order to perform S0-024-001, the Diesel Generator Monthly Operability Test.
The engine was idled until 0926, at which time it was synchronized to the grid and loaded to 4.1 MW with 32 kilovars of reactive power leaving the generator
(+32 kvars). The operator observed steady operation, and left the diesel generator controls.
At 0931, the operator checked operation of the D/G and noticed that reactive power was -200 kvar and power had increased to 4.4 MW.
While attmpting to increase kvar to a positive value, he noticed an increase in power and amperage. He then atts pted to reduce power by operation of the governor control switch. However, the engine tripped on Generator Ioss of Field prior to the operator gaining control. At 0945 hours0.0109 days <br />0.263 hours <br />0.00156 weeks <br />3.595725e-4 months <br /> the 'A' D/G was declared inoperable and the Limiting condition for Operation (LCO) for Technical Specification 3.8.1.1 was entered.
The initiating event in this incident appears to be a voltage schedule change which occured at the Mountour Steam Electric Station (MSES). The MSES is at one end of the Montour-Mountain 230 kv transmission line, to which the 'A' diesel generator was connected via the on site distribution systm. The voltage on the Montour-Mountain line was increased frm 237 kv to 239 kv at approximately 0930 hours0.0108 days <br />0.258 hours <br />0.00154 weeks <br />3.53865e-4 months <br />. This created a voltage mismatch between the diesel generator output and the anergency Safeguards Systen (ESS) transformer output.
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This voltage mismatch caused VARS to flow into the generator and caused the generator's voltage regulator to attmpt to decrease the generator teminal voltage by reducing the field current. Since the diesel generator is essentially ccrnpeting against an infinite grid, it cannot reduce teminal voltage without reducing field current to a value below its trip setpoint.
Hence, the D/G tripped on generator Loss of Field, which is triggered by low current frcm the voltage regulator to the field.
Inmediate corrective actions consisted of the following:
1.
MSES was contacted to determine if a voltane change had taken place.
It was confirmed that voltage increased 2kv at approximately 0930 hours0.0108 days <br />0.258 hours <br />0.00154 weeks <br />3.53865e-4 months <br />.
2.
The governor and voltage regulator were monitored with stripcharts during a test run ccamencing at approximately 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br />. No hardware problms were found.
3.
The implications on nuclear safety were evaluated given the available information. The evidence strongly supported that the emergency operation of the diesel generator was not impaired; only the stability of the machine while paralleled to the grid in the test mode was in question.
4.
The monthly operability test was ccmpleted, the diesel was declared operable and ICO 3.8.1.1 was cleared at 1740 on 10/30/86, approximately 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> after the ICO had been incurred.
'Ihe D/G responded per design when subjected to voltage disturbances on the grid. It should be noted that the D/G is not parallelled to the grid in mergency conditions and therefore the D/G's ability to perform under emergency conditions was not impaired. Based on the above, this event is considered to be a non-valid failure.
To prevent recurrence of this event, steps will be added to operating procedures and surveillance procedures, as appropriate, to ensure there will be no planned grid voltage changes scheduled during diesel generator test runs.
As of October 30, 1986, the "A" Diesel Generator Start Iog indicated there were two (2) diesel failures in the last 100 starts. The "A" didsel test int al is one start ev 14 days per Regulatory Guide 1.108, Section C.2.d.
.M. Crinmins Jr.
Superintendent of Plant-Susquehanna TSR/cdn cc: Mr. L Plisco Senior Resident Inspector U.S. Nuclear Regulatory Ccmmission P.O. Box 52 Shickshinny, PA.
18655 U.S. Nuclear Regulatory Ccumission Document Control Desk Washington DC.
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