Breaker failure relays are referred to as back-up protection devices which are applied as stoppage protection relays for the most relays. As case in point Breaker failure relay is employed as a backup device for differential relay of an influence Power Transformer and additionally for distance relay of a conductor.
Why Breaker Failure Relay is required?
In the fault condition of any equipment it's expected that the fuse of this instrumentality are going to be tripped by main protection relays of such instrumentality if there's a failure within the tripping circuit of the fuse or within the fuse itself. During this case the fuse won't tripped then, to isolate this fault, the bus bar at that this equipment is connected should by fully isolated by tripping all the equipment connected thereto by a delayed time. Then, the sole connected equipment to the current bus bar is that the faulted one. During this case, the faulted equipment has no current transient through it thus, it’s often disconnected manly by isolates.
How Breaker Failure Relay Operates
To operate breaker failure relay it should satisfy three conditions. They are;
- Tripping signal from any main protection relay of the condemned equipment which exist.
- Fuse of the condemned equipment continues to be connecting (n.o. auxiliary contact from fuse is used).
- There’s current passing through this equipment not withstanding its value is incredibly tiny.
Although one amongst the second and third conditions are spare for healthy operation of breaker failure relay, it's desirable to use each for a lot of security.
The schematic arrangement shows the breaker failure relay circuit. Tripping circuit of breaker failure relay is analogous to tripping circuit of bus bar protection relay. Generally breaker failure relay could use an equivalent tripping circuit of bus bar protection relay.