Trip Circuit Supervision in Circuit Breakers

Trip circuit supervision in Circuit breakers is an vital part of any protection scheme. If the trip relay fails to operate, it may result in upstream tripping or even in damage to equipment.  Trip circuit supervision makes sure that the tripping coil of a circuit breaker is always in the healthy condition.  

The Trip circuit supervision is particularly important in breakers which have only one trip coil.    The Trip circuit supervision relay continually measures the resistance of the trip coil of circuit breakers.  It also measures the control voltage of the trip coil and gives and alarm when the control voltage falls to low levels. 

The Trip circuit supervision relay injects a constant current through the trip coil of the breaker and measures the voltage drop across the coil.  Thus, the relay is able to measure the resistance of the coil.  

The Trip circuit supervision relays can also monitor more than one breaker coil. 

If the Trip circuit supervision Relay detects a fault, it activates the breaker failure logic which can activate a backup breaker if installed or cause the tripping of upstream breakers.


  1. g harper10:01 AM

    As posted the TCS relay is an important relay incorporated in the protection system which is often overlooked .
    The ubiquitous CEE TAX does have the function of remote alarms but in my experience is rarely installed with only the flag indication issued when the shunt coil has failed.
    With the ever increasing ageing of breakers coils can be easily burnt out with sticking toggle mechanisms etc.

  2. Aditya11:24 AM

    Why delta connected motors are mostly used for low tension supply


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