Improved input signals to the polarised-mho distance relay

The paper examines the polarising signals used in British and Continental distance protection schemes, in an attempt to optimise the resistive reach of the polarised-mho relay, and also minimise the possibility of overreaching during zone 2 resistive faults. Dual and single polarisation schemes are investigated and alternative schemes with improved protection characteristics are suggested. Relay performance, during `reverse¿¿ phase-to-phase faults, is considered, and a simple procedure is given to establish a relay characteristic for a `reverse¿¿ fault.