Circuit Breaker Tripping Schemes
Basically two types of tripping schemes which are given below:-
- Relay with make type contact.
- Relay with break type contact.
1) Relay with make type contact:
In this scheme, the relays are connected in the stare, and contacts of each relay are connected in parallel and this parallel unit of contacts is connected in series with breaker trip coil to battery supply.
Now we describe, how does trip the breaker when a fault occurs on any of the phases, the relay will close the contact by which the tripping circuit is completed hence the trip coil of the breaker is energized which opens the circuit breaker along with its auxiliary switch. When the supply of current to fault path is stopped, the relay contact comes to normal position, then the trip coil is de-energized. The schematic drawing of the above scheme is shown in the figure.
2) Relay with break type contact:
In this type of scheme, the tripping circuit drives energy from the main supply source through C.T’s secondary coil. The relay elements and the trip coil of each phase of the circuit breaker are connected in series and are connected as to form a star connection. Now we describe how the circuit breaker breaks at fault condition.
At normal condition, the relay contacts are closed and hence no current flow through the breaker trip coil. When a fault occurs, the relay contacts are opened and circuit breaker trip coil is energized to open the circuit breaker. The schematic drawing of the above scheme is shown in the figure.