Subcycle transmission line protection using time-domain similarity measure

Abstract

Fast fault clearance on transmission line is desirable for the power system operating near stability margins to ensure transient stability, power quality and minimize thermal stress on the equipment. A time-domain similarity based pilot line protection scheme using sampled data of currents is proposed in this work. Fault component of currents from both the line terminals flow into the line during an internal fault. For external fault situation, current flows into the line at one side and out of the line at other side. This property is utilized in the proposed scheme. Once a fault is detected, time-domain similarity computed between the two instantaneous incremental currents is used for identifying internal fault. Sensitivity of the method is evaluated for noise, current transformer saturation and unsynchronized measurements. Results confirm the effectiveness of proposed scheme in terms of speed advantage and security.