Directional Relaying Applying Phase Quantities of Current Traveling Wave and Prefault Voltage

A traveling wave-based line protection scheme identifies the direction of fault by comparing the polarities of prefault modal voltage and modal current wavefronts appearing at the relay location. Analysis of modal components involves more signals (six voltages and six currents) compared to the phase domain signals (three voltages and three currents), which burdens the hardware circuitry at high sampling rates (1 MHz) used for traveling wave extraction. In this paper, an improved solution for the directional relaying scheme is proposed by utilizing the prefault phase voltage samples along with phase current traveling waves, thereby avoiding the analysis of modal networks and reducing the associated computational burden. The method is not affected by the transient response of capacitive voltage transformers, and a high sampling rate for voltage signals is not required. Its performance is evaluated by simulating various faults on a 400 kV transmission network in PSCAD and found to be promising.