New approach to distance protection for resistive double-phase to earth faults using adaptive techniques

Distance protection is prone to mal-operation under resistive double-phase to earth fault conditions. This is caused by the relay measuring the incorrect impedance to the fault due to the influence of infeed from the remote end of the line. The paper describes two adaptation techniques, one for use with the earth elements, and one for use with the phase elements, which enable the correct impedance to be measured, and hence improve distance protection performance under such fault conditions