Information Notice No.80-31 - Maloperation of Gould-Brown Boveri 480 Volt-type K-600s and K-DON 600s Circuit Breakers

                                                       SSINS No.: 6870  
                                                       Accession No:  
                                                       IN 80-31 

                               UNITED STATES 
                           WASHINGTON, D.C. 20555 
                              August 27, 1980 

Information Notice No. 80-31:   MALOPERATION OF GOULD-BROWN BOVERI 480 
                                   VOLT-TYPE K-600S AND K-DON 600S CIRCUIT 

Description of Circumstances: 

The Cincinnati Gas & Electric Company reported problems with the Gould-Brown
Boveri Type K-600S and K-DON 600S circuit breakers used in 480 volt a.c. 
circuits at the William H. Zimmer nuclear stations. The problem involved 
inadvertent circuit breaker closure during operation of the breaker charging
springs when the breaker was racked out to the test position. 

The problem resulted from the use of undersized bushings in the circuit 
breaker secondary close latches. The undersized bushings caused the 
secondary close latch to hang-up on the shunt trip device resulting in an 
inadvertent circuit breaker closure when the spring charging motor was 

The vendor has stated that the problem does not exist during normal 
operations with the circuit breaker in the connected position. 

Recommended Action for Licensees and Holders of Construction Permits: 

All licensees of operating nuclear power reactors and holders of 
construction permits should be aware of the potential problems described 
above. The vendor has stated that a small number of circuit breakers were 
assembled with undersized secondary latch bushings between 1969 and 1977. It 
is recommended that the following actions be taken: 

(1)  Determine if the subject circuit breakers are installed in any safety-
     related application at your facility. The affected circuit breakers are
     manufactured by Gould-Brown Boveri and are types K-600S and K-DON 600S,
     480-volt a.c. electrically operated, drawout type with static trip 

(2)  If it is determined that your facility has the circuit breakers 
     described in Item (1) above, perform the K-600S, K-DON 6005 Field Test 
     Procedure attached to this information notice (Gould-Brown Boveri 
     I.B.-9.1.7-6 Issue F, Addendum 2, dated March 4, 1980). 

(3)  If maloperation of the circuit breaker occurs during performance of the
     field test procedure described in Item (2) above, perform the 
     corrective action described in the attached field test procedure 
     (installation of a 0.050 shim to the secondary close latch and retest 
     of the circuit breaker). 

                                                            IN 80-31  
                                                            August 27, 1980 
                                                            Page 2 of 2  

No written response to this information notice is required; however, if 
additional information is required, contact the Director of the appropriate 
NRC Regional Office. 

Excerpt from Gould-Brown Boveri 
  Letter to NRC Region III dated 
  June 2, 1980.


Page Last Reviewed/Updated Thursday, March 25, 2021