Application of block pulse functions in a polyphase digital distance relay

This paper presents a digital distance relay scheme for power transmission line protection. The scheme uses a single criterion to determine the fault distance during the ten types of shunt faults on a three-phase transmission line. The criterion is derived using a modal transformation. The scheme uses a recently developed algorithm based on block pulse functions to compute fundamental frequency voltage and current phasors of fault signals. The scheme is tested using simulated voltage and current signals obtained from the electromagnetic transient program (EMTP). These simulations are performed on a 230 kV transmission line of a six bus power system model