A fast adaptive digital distance protection

This paper presents a new adaptive technique which can improve the performance of digital distance protection under high resistance earth fault conditions. In this technique, the relay operating characteristic is divided into certain and uncertain fault regions. The certain region is a preset fixed region which is obtained by the system studies under different operating conditions. The faults in the certain region are tripped quite instantly. However, for the other faults an adaptive routine is instigated which uses prefault system data available from a low speed communication channel such as SCADA or RTU. The distance relay with necessary data can provide a reliable trip decision for the whole line length in zone-1 setting. The results of computer simulation show the improvement of sensitivity and selectivity of the relay.