Microprocessor-based algorithm for high-resistance earth-fault distance a protection

A new method for high-resistance earth-fault distance protection, capable of calculating fault distance independent of fault resistance, is presented with an accuracy analysis which shows that calculation accuracy, which depends on various application parameters, may be uniquely established by a measurable index. Relay overreach is avoided by reference to the index. Conclusions aredrawn from results of laboratory tests of a microprocessor implementation of the algorithm. The resistive tolerance is found to depend on the actual application parameters, but may be as much as four times the forward relay setting at the exporting end of a typical line.