ML20024B784

Followup Interim Rept Re Potential Deficiency in 5HK Switchgear Supplied by Brown Boveri.Circuit Breaker Inadvertently Closed & Tripped Following Spring Charging. Light Spring Added to Close Latch

ML20024B784
Person / Time
Site:	Limerick, LaSalle, 05000000
Issue date:	04/28/1983
From:	Duvall D BBC BROWN BOVERI, INC. (FORMERLY BROWN BOVERI CORP.
To:	Stello V NRC OFFICE OF INSPECTION & ENFORCEMENT (IE)
Shared Package
ML20024B778	List: ML20024B777 ML20024B784 ML20024B788
References
10CFR50.55(E), NUDOCS 8307110377
Download: ML20024B784 (2)

Text

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mmc. srown soven. eiectn.c, inc.

m taom. cost m Man /acturer of I-T E Electrical Power Ecepment April 28, 1983 Mr. Victor Stello, Jr. , Director Office inspection & Enforcement U. S. Nuclear Regulatory Co==ission

.. Washington, D. C. 20555

Reference:

Limerick Generating Station Philadelphia Electric Co:pany Significant Deficiency Report No. 74 Dated March 24, 1983

Dear Mr. Stello:

This is a fc11ow-up report to an interin 10CFp.50.55(e) report filed by the Philadelphia Electric Company with regard to a potential deficiency in SEK switchgear supplied to the Limerick Generating Station by Brown Boveri Electric. This report was filed with the Office of Inspection & Enforce =ent, Region I.

The report stated, "During pre-operational testing, one breaker inadvertently closed following completien of the spring charging and , two others spontane-ously and continuously closed and tripped following the spring charging cycle." The circuit breakers were returned to Brown Boveri Electric for evaluation of the reported problems. This evaluation revealed that the

.second probica, wherein it was reported that the circuit breakers closed and tripped spentaneously and continuously following the spring charging cycle could not be duplicated. This condition can occur if the racking screw is not properly positioned in the " connected", " test" or " disconnected" position.

This second reported condition was deter =ined not to be a problem.

The first condition wherein it was reported that the circuit breaker inadver-tently closed following cc:pletion of the spring charging was deter =ined to be an intermittent problem on this one circuit breaker. The condition was corrected by adding a light spring to the close latch in the circuit breaker "

operating techanism. The addition of this spring forces the clearances in the close latch and associated linkages to be taken up in one direction.

This reduces the shock from the latch and linkage's so that when the close latch roller, which is part of the cas assembly, is driven by the closing springs at the end of the charging cycle hits against the close latch, the latch is held and does not slip.

The sane basic operating mechanism is used on all E3E HK circuit breakers.

This includes the SEK, 7.5HK, 15HK and the 3SHKV circuit breakers. The HK 7

circuit breakers have been in production since hpprcxt ately 1961. Some of

!' 0307110377 830707 see.u symmi oinsion PDR ADOCK 05000373 Sonng House, PA 19477

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. 3BC 24 6 % ioviE' Brown Boveri Electric, Inc.

Mr. Victor Stello, Jr.

April 28, 1983 Page 2 the early 3SHKV circuit breakers which first wcnt into production in 1973 experienced a slipping close ?stch which was thought to be caused by the heavier closing spring load. It was at this tine that a light spring was added to the close latch of the EK operating rechanism. The spring is identified as Part No. 162374-A.

Tro= the time of initial production in 1961 up until 1973, this clese latch anti-shock spring was not us.ed in the =echanis: of the EK circuit breakers because there was no evidence of the close latches slipping. This spring was added to all EK circuit breaker =echanisms in October of 1973 and was included in production circuit breakers until June of 1975. In June of 1975, the spring was ocitted on all 5, 7.5 and 15EK circuit breakers because the lack of occurrences of slipping latches did not warrant its centinued use.

In June of 1977 because of production changes, the spring, again, was added to all EK circuit breakers. The spring has been used centinuously en the 38EKV circuit breakers since 1973.

The condition, wherein af ter the close spring charge, the circuit breaker closes unintentionally without initiation of the manual or electrical clese operation, was experienced intermittently on one circuit breaker out cf approximately 150 EK circuit breakers at the Limerick Generating Station.

The condition, once experienced, cay not occur again for 50 to 75 operations of the circuit breaker. Because of the infrequenc:. of this condition occur-

' ring, the condition may go unnoticed by =any users.

Instructicas for the installation of the close latch anti-shock spring in the EK cechanism are contained in Brown boveri Electric 13-5307. A copy of this instructicn book is enclosed with this letter. Erewn EcVeri Electric will no*1fy the users of HK circuit breakers of how to correct this condition if i; d ' detected or to add the spring at the regularly scheduled maintenance ins ci-;da.

l f C' s b'

D. . DL*VALL Vic " Tdent EWR/jn Enclosure e

cc: A. V. Boetticher W. E. Laubach E. W. Rhoads L. H. Sch=idt J. R. Silverio