ML20070C763
| ML20070C763 | |
| Person / Time | |
|---|---|
| Site: | Mcguire, Fermi, Grand Gulf, Susquehanna, Limerick, San Onofre, Cook, McGuire, 05000000, Zimmer, Shoreham |
| Issue date: | 12/10/1982 |
| From: | Duvall D BBC BROWN BOVERI, INC. (FORMERLY BROWN BOVERI CORP. |
| To: | Stello V NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| References | |
| REF-PT21-82-749-000 PT21-82-749, PT21-82-749-000, NUDOCS 8212140330 | |
| Download: ML20070C763 (2) | |
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Brown Boveri Electric, Inc. .
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Mr. Victor Stello, Jr., Director Office of Inspection & Enforcement U. S. Nuclear Regulatory Commission Washington, D. C. 20555
Dear Mr. Stello:
This report is to identify a potential problem with Brown Boveri Electric (formerly ITE) low voltage circuit breakers equipped with solid state trip Jevices only. This potential problem may also be reported by Southern California Edison Company, San Onofre Units 2 and 3.
Four (4) solid state trip units were received from San Onofre Nuclear Units 2 and 3 on November 11, 1982.
As received, the trip units would not perform a trip function. Careful inspection and test of all units determined that capacitor C205, which is a filter capacitor in the power supply circuit, was non-functioning. This Sprague type 40D, 20 af capacitor was replaced with a new type capacitor and each unit then functioned perfectly in c11 respects.
An inspection and analysis of the type 40D capacitors showed that in every case the capacitor was made ineffective from long term degradation. Three of these capacitors were sent to our supplier, Sprague Electric for inspection.
Their analysis showed the capacitors damaged by internal corrosion of the internal aluminum elements indicating attack by a halogenated compound such as those used in conemercial solvents. It was stated that these solvents, under certain conditions, can penetrate the, elastomer seal (non-hermetic) at the end of the capacitor and attack the aluminum.
A study of our records shows that the use of the type 40D capacitor was dis-continued on August 17, 1976 when a change was made to a higher temperature unit, Sprague type 137D, (22 af). The design change was made because of electrical d.amap to the type 40D capacitor experienced in several applica-tions in chemical plants. The circuits in the chemical plants on which those units were damag'ed, were feeders to loads consisting of heavy current SCR drives. These were determined to cause the primary load current to be very distorted (non-sinusoidal). The non-sinusoidal primary current placed an undue stress on these capacitors due to excessive AC ripple in the power supply circuit. At that time the type 137D (higher temperature rated) caps-citor unit had just been,placed on the market and was adopted as standard in all of our solid state trip units. The type 137D capacitor is hermetically sealed, which precludes the recurrence of the contamination problem experienced with the four (4) Southern California Edison units.
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' . .?. C December 10, 1982 Page 2 i Serisi so1N state trip units with a serial number below 28300 are suspect.
numbers above 28300 have the 137D capacitor installed. D e serial number is 4
shown on a tag on the side of the trip unit.
For For trip units packaged in a gray case the capacitor is designated C205. .
trip units packaged in a red case the capacitor is designated as C4.
The ultimate failure condition of the capacitor is an open circuit. At this point the trip unit will not respond to an overcurrent condition (i.e. will not trip the breaker). During the initial stages of degradation it inay be possible to get nuisance operations for load currents below the pick up settings.
This failure condition should be uncovered by routine testing of the trip unit with the ITE type 504 test set, however, test sets with serial numbers below 260 may not be able to detect the condition. Users with test sets below serial number 260 should check with the manufacturer to determine if the test set needs modification.
This condition is possible on Brown Boveri Electric (formerly ITE) low voltage power circuit breaker with solid state (static) trip devices only. Records indicate that these are located at the following Nuclear Stations.
Detroit Edison Company Fermi Long Island Lighting Company Shoreham M],f "5 0.
D 3 Duke Power Company McGuire \t Philadelphia Electric Company Limerick 3 q ,y V Y
Indiana & Michigan Cook Mg Cincinnati Gas & Electric Zissner Pennsylvania Power & Light Susquehanna W-@ t Southern California Edison , San Onofre Units 2 & 3 % u*
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Mississippi Power & Light
. . Grand Gulf Unit #1 only g4 8
l RECOMMENDATION It is recommended that suspect trip units be tested to determine that they are operating roperly. If the test is to be made with the ITE type 504 test set, the use. sold verify that their test set has the capability to detect this con 1.o ..
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/ cc: Wolfgang Lauden
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