A new directional relay for the protection of distribution feeders

This paper presents a new directional relay for distribution feeder protection by utilising fault generated high frequency transient voltage and current signals. In the scheme, a specially designed high frequency voltage transducer is used to capture the fault generated voltage transient signals; transient current is extracted through the CTs. The signal processing unit of the relay first scales the captured voltage and current signals to a comparable level from which the differential and average signals are derived; Comparison between the energies of the two signals will determine the direction of a fault. A 33 kV distribution system is modelled by EMTP software, the faulted responses of which are examined with respect to different system configurations and fault conditions. The results show that the scheme is able to give correct response under various system and fault conditions