Common Terms in Relay Protection

Common Terms in Relay Protection are

Pick Up Value

Pick up Value of relay  refers to the value above which the relay will generate the alarm or the trip

Operating Time

The Operating Time is the time which is allowed to elapse after the pick up value has been exceeded before the output is given. 

Reset Value

Once the relay operates, it has to be reset.  The relay resets after the measured value falls beyond a certain value.  This value is below the pick up value in case of functions such as overvoltage or overcurrent.  In case of functions such as undervoltage or underfrequency, this value is above the pick up value

Reset Time delay

Reset Time delay is the time taken by the relay to reset after the reset value has been reached.

Reach of the relay

This is a term used in distance protection.  The distance Relay operates when there is fault in a cable.    Reach of the relay refers to the distance till which the relay can sense the fault.