ML18057A317

Provides Summary of Upgrades Made to Plant Electrical Distribution Sys,Per 870714 Loss of Offsite Power Event When Inadvertent Actuation of Water Deluge Spray Sys for 1-2 Startup Transformer Resulted in Bus to Ground Fault

ML18057A317
Person / Time
Site:	Palisades
Issue date:	07/03/1990
From:	Smedley R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9007060210
Download: ML18057A317 (4)

Text

consumers Power POWERiNii MICHlliAN"S PROliRESS General Offices: 212 West Michigan Avenue, Jackson, Ml 49201 * (517) 788-0550 July 3, 1990 Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT -

SUMMARY

DESCRIPTION - ELECTRICAL DISTRIBUTION SYSTEM IMPROVEMENTS During May 1990, the NRC Palisades Project Manager requested a submittal which summarizes the recent upgrades made to the Palisades Plant electrical distribution system. The following provides that summary and a reference to the event which initiated them.

On July 14, 1987 the Palisades Plant suffered a loss of offsite power event (LOOP) when the inadvertent actuation of the water deluge spray system for the 1-2 start-up transformer resulted in a bus to ground fault. The plant was without offsite power for approximately 7 and one-~!yf hours. This event was reported to the NRC per 10 CFR 50.73 as LER 87-024 . Although there was no danger to the health and safety of the public as a result of this event, Consumers Power Company committed to conduct an engineering evaluation of the off site power system to identify possible options to improve the reliability of the system.

On September 24, 1987, Consumers Power Company submitted a letter that described the results of the engineering evaluation of the offsite power system and described the ~zyions that would be taken to improve the

• The follo~~~~ ~odifications were undertaken as reliability of the system part of Facility changes FC-799 & FC-800 4 .

1. A 345 - 2.4 kV transformer tied to the switchyard "F" bus was located in the Palisades switchyard to provide a physically independent source of power to the plant 2400 volt buses including the safeguard buses. The connection between the plant and this new transformer is via an underground cable that provides for separation from the preexisting overhead lines. The new transformer is designed to be the normal source of power to the plant safeguards buses during routine plant operating conditions. This modification was completed during the Fall 1989 maintenance outage.

OC0690-0042-NL04 A c.M5 ENERGY COMPANY

Nu~iear Regulatory Commission 2

• .** 'Big Rock Point Plant Elec Dist System Improvements July 3, 1990

2. The bolted link disconnects located in the main generator isophase bus were replaced with a motor-operated disconnect switch in May, 1990. This modification significantly decreased the time required to allow backfeeding power through the main transformer to the station power transformers. Prior to this modification approximately 4 to 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> were required to reconfigure the plant to allow backfeeding. The modification has reduced the time required to less than 30 minutes.

3. An existing spare transformer was installed as station power transformer 1-3 and is being used to supply power to the plant cooling towers during normal operation replacing startup transformers 1-1 and 1-3 as the primary power supply for the cooling towers. This new configuration eliminates dependence on the "R" bus as the only source of power for the cooling towers, installed in November 1988.

The attachment to this letter provides a schematic drawing of the present offsite power configuration of the Palisades Plant.

Richard W Smedley s;:>~

Staff Licensing Engineer CC Administrator, Region III, USNRC NRC Resident Inspector - Palisades Attachment References

1. LER 87-024 - "Startup Transformer Failure Results in Loss of Offsite Power and Manual Reactor Trip", August 13, 1987

2. F. W. Buckman, VP-NOD, Consumers Power Company to D. M. Crutchfield, NRC -

"Plant Modifications to Improve Offsite Power Reliability", September 24, 1987.

3. FC-799, Station Power Transformer 1-3 Addition, GW0-8303

4. FC-800, Offsite Power Reliability Improvement, GW0-8303 OC0690-0042-NL04

-- I ATTACHMENT Consumers Power Company Palisades Plant Docket 50-255 OFFSITE POWER ARRANGEMENT July 3, 1990 1 Page OC0690-0042-NL04

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