Relay performance verification using fault event records

Event reports recorded by intelligent electronic devices (IEDs) such as digital relays and fault recorders during disturbances depict the status and system parameters of the power system. Incorrect relay settings and unknown system parameters can lead to relay misoperation but information regarding these are available by performing a comprehensive analysis of fault records. Hence, it is necessary to regularly make a comprehensive assessment of the functioning of the relay to ensure reliable operation. The objective of this paper is to demonstrate various aspects of evaluating relay performance and verifying circuit parameters which are used in relay settings using field data in two case studies. While scrutinizing the relay’s operation, this paper also presents key insights on verifying circuit parameters using the same relay event records. The lessons learned from the case studies presented in this paper will equip a protection engineer to inspect the operation of a relay during a transmission line fault, help gain a better understanding of the fault event and take possible actions to prevent future occurrence of similar events.