Time delay function of a relay defines the tripping time during which the fault signal is suppressed for the relay to re-energize again for the system to be back for operating within the operating ranges of the parameters. This function helps avoid the unrestrained differential parameter that can damage the system. The monitoring relay’s time delay is set to co-ordinate with the time delays of other protection relays for overall system performance and the grading of the time delay of the different relays can be set according to the parameter sensitivity.
