ML20082N398
| ML20082N398 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 04/21/1995 |
| From: | Ray D COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9504250201 | |
| Download: ML20082N398 (2) | |
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Commonweahh Illison Company
[h laSalle Generating $tation 2601 Nonh 21st Road Wrwilles. IL 61311a>757 Tel 815-3574761 April 21,1995 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C.
20555 This special report is subrnetted in accordance with LaSalle Unit 2 Operating License NPF-18, Appendix A, and Technical Specifications 4.8.1.1.3 and 6.6.c regarding the Unit 2B Diesel Generator (E22,2E22-S001), manufactured by Electro-Motive Division of General Motors Corporation (Model EMD 20645E4).
On March 24,1995, with LaSalle Unit 2 defueled, the Unit 2B Diesel Generator (DG) was operating in accordance with LaSalle Technical Surveillance LTS-500-211, " Unit 2 Division 3 Emergency Core Cooling Systems (ECCS) Response Time Surveellence". At approximately 1959 hours0.0227 days <br />0.544 hours <br />0.00324 weeks <br />7.453995e-4 months <br />, the Nuclear Station Operator (NSO) attempted to synchronize the 2B DG with the offsite power source while the generator was loaded with its emergency loads. At approximately 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br />, the 2B DG experienced a loss of excitation and subsequently tripped due to this condition. The emergency loads on the 2B DG were successfully transferred before the 2B DG tnpped. This, failure was not a valid failure in accordance with Regulatory Guide 1.108 and Technical Specification 4.8.1.1.3.-
The 2B DG voltage regulator has infomal circuitry which allows parallel generators to share reactive load and reduce reactive currents between them (voltage droop j
and compensation), in this case, the paralishximachines would be the 29 DGet an infinite bus (utility power grid). This droop circuit is adjusted to reflect normal i
test conditions, i.e., paralleling an unloaded diesel generator to an infinite bus. The initial conditions for this event were different than normal test conditions; the diesel generator was being paralleled to an infinite bus while carrying a large inductive load.
Under these conditions, the voltage droop circuit will allow tho' diesel generator output voltage to seg approximately 6% during the paralleling process. To compensate for this condition, plant procedures have the diesel generator voltage raised higher than the grid voltage during the paralleling process. During this event, this compensatory measure was not satisfactory, and the diesel generator voltage dipped below grid voltage, resulting in reactive current flow into the machene. The machine could not increase field excstat;on fast enough to recover from this event and tripped on loss of excitation.
9504250201 950421 PDR ADOCK 05000374
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PDR A Unkum Compan)
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- e. i The operating procedures will be changed to accommodate this specific condition by giving guidance for paralleling a fully loaded 2B Diesel Generator to the offsite a
power source.
- Sincereh, D.J. Ray Station Manager LaSalle County Station DJR/CTK/lja ec:
NRC Region lli Administrator NRC Senior Resident inspector INPO - Racords Center IDNS Resident inspector Nuclear Licensing Administrator l