ML19296A732

Final Deficiency Rept Re Lightning Arrestors in 480-volt Load Ctrs Causing Reading Below Manufacturer Recommended Min Value.Cause Unstated.Damaged Arrestors Will Be Replaced & Resistance Checked

ML19296A732
Person / Time
Site:	Summer
Issue date:	02/11/1980
From:	Crews E SOUTH CAROLINA ELECTRIC & GAS CO.
To:
References
NUDOCS 8002150345
Download: ML19296A732 (2)

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c....u.. ... c.. ... cr Feb ruary 11, 1980 Mr. James P. O'Reilly, Director United States Nuclear Regulatory Commission Region II, Suite 3100 101 Marietta Street, NW Atlanta, Georgia 30303

Subject:

Virgil C. Summer Nuclear Station Reportable Significant Deficiency Nuclear Engineering File 3.1051

Dear Mr. O'Reilly:

On 2/4/80 a significant deficiency was reported to Mr. Jack Skolds, NRC resident inspector, by J. A. Wactor of SCE&G. The deficiency concerns lightning arrestors in the 480 volt load centers. This was previously reported as a potential significant deficiency in a 9/27/79 letter from Mr. M. C. Johnson of SCE&G.

The deficiency was first discovered 8/13/79, when a routine resistance check of the load center transformers revealed readings below the manufacturer's recommended minimum value. The low readings were traced to the lightning arres-tors. The load centers were manufactured by Gould, with McGraw-Edison as sub-vendor for the arrestors.

The suspect lightning arrestors were replaced and sent to Gould for in-spection and then forwarded to McGraw-Edison for testing. Resistance readings were taken more often on the switchgear and a drop in the resistance of the units was noted each time. Representatives of Gould and McGraw-Edison visited the station and were given the data obtained and took more arrestors for inspec-tion and testing.

The tests on the returned arrestors revealed four defective arrestors, two of which were from non-safety related load centers. Four arrestors were damaged in transit and were not tested. The defective arrestors had a crack in the lower seal that allowed moisture to get into the arrestors. The remain-der of the arrestors tested by McGraw-Edison were good. Additional testing by Gould and ITE revealed that the drop in resistance readings were caused by tem-perature effects on the insulation. As a result, the instructions for resistance checking the transformers has been revised to take temperature into account, and the arrestors are disconnected and checked separately.

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Mr. James P. O'Reilly Feb ruary 11, 1980 Page Two Although there is no inherent problem with the arrestors as first suspected, we consider the item reportable under 10CFR50.55(e) due to the cracked seals. The damage most likely occurred during manufacturing or in transit to the station. Failure of the arreators could have resulted in loss of redundant safety related power supplies. We have requested that Gould consider reporting the incident under 10CFR21.

Corrective action involves rep' acing the damaged arrestors and re-sistance checking the arrestors separately to see that they meet the manu-facturer's requirements. This has been done and no problems have been reported to date. Based on this, SCE&G coasiders this a final report on this item.

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e r y yours,

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E.'E. ews, Jr. ,-

JAW:EHC:rh cc: Office of Inspection and Enforcemant (Washington, D. C. )

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