Impact of long duration faults on out-of-step protection

This paper focuses on the impact of long duration faults in high voltage integrated networks. It endeavours to show that the position of faults in the power system could result in unnecessary blocking of impedance relays, as well as unwanted operation of out-of-step relays during the actual fault disturbance. Out-of-step relays are required to operate during a power swing condition, which is often caused as a result of a system fault.