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Protection Riddle No.102 - Dead Machine Protection
Dear Sir,
Can you inform why we can not use the parallel combination of field breaker 52a contact & Field U/V relay's NC contact ( which will close on field U/V )  in series with the HV Ckt.Bkr closing circuit so that it becomes impossible to back energise the Generator ? Instead we normally use 50/27 combination of the AC ckt of the generator.
Thanking you,
Yours Sincerely,
Imran
Author : Imran Mushtaque - From: India
 
#1
Wed, April 17th, 2013 - 10:33
Generally two auxiliary contacts are used in series with circuit breaker closing coil as illustrated below. Where 52b is normally close auxiliary contact of circuit breaker to prevent closing coil burning and R is normally close contact of latch trip relay to prevent mal-operation of system.

 
Author : Hamid - From: Iran
 
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