What is the function of restraining coil in differential
relay? as well as restraining current?
Answer Posted / arvind manavazhagan
The concept is very simple. If we consider any relay there are two forces namely controlling and deflecting force.Both the forces are present during normal operation also. Controlling force keeps the contacts of a relay in normal position during normal operating conditions.When a fault occurs we know that due to a reduced impedance high fault current may flow through the circuit and hence through the secondary of the CT that is connected to the relay also.This in turn increases the deflecting force than the controlling force thus operating the relay.Controlling force is produced by the restraining coil and deflecting force is produced by restraining coil.
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