Generalised method of assessing polarising signals for the polarised-mho relay

This paper considers existing methods of assessing the position of the steady-state operating characteristic of the polarised-mho relay in the R-X diagram, and puts forward an improved generalised method which is ideally suited to computer simulation studies. The new method is applied to existing schemes of protection employed by two British and two Continental relay manufacturers. Consideration is also given to the influence of system earthing on the characteristics of earth fault relays, and a compensation scheme for resistance earthed systems is suggested.