There are two Tripping Circuits in the Breaker, Called a Trip Circuit 1 and Trip Circuit 2. Both this Tripping Circuits should have different DC Supply and different Tripping. 

Tripping Circuit of VCB can be divided into Four parts:

  1. Local Control  through the Local TNC Switch in Breaker
  2. Remote Control through the Remote TNC Switch in CP/RP
  3. Automatic Tripping through Protection Relay
  4. Monitoring through the TCS Relay in CP/RP

Local Controlling:

  1. A Breaker can be Tripped Locally in the yard through Breaker TNC Switch. For this we have to keep Local/Remote Switch in Local Mode and turn the Breaker TNC Switch to C Position.

Remote Controlling:

  1. A Breaker can be Tripped Remotely from the Control Room through the TNC Switch in the Relay Panel/Control Panel and through the SCADA System. 

Protection Tripping:

  1. Breaker Trips Automatically for Protection when the Master Trip Relay is Operated.

Monitoring:

  1. Breaker Tripping Circuit is Continously Monitored for Healthiness through, Trip Circuit Supervision (TCS) Relay in the Relay Panle in the Controol Room.
There are following Elements in the Tripping Circuit:

  1. Tripping Coil
  2. Remote Control through the Remote TNC Switch in CP/RP
  3. Automatic Tripping through Protection Relay
  4. Monitoring through the TCS Relay in CP/RP

Tripping Coil:

  1. A Permanant Negative (K2) is given to one end of the Tripping Coil.
  2. When Positive is received by other end of the Tripping Coil through the TNC Switch, the Tripping Coil gets energised and attracts the Tripping Plunger which then attracts the Tripping Mechanism and the Breaker Trips.

Tripping Resistance:

  1. A Resistance is used just before the Tripping Coil.

NO Auxillary Contact (52a):

  1. Before the Tripping Resistance, we use NO Breaker Auxillary Contact 52a as an Interlock.
  2. When the Breaker is in OFF Condition, 52a does not allow, the Breaker to be closed. In other words, when the Brekaer is OFF, tripping command cannot reach the Tripping Coil.