Power-system studies for the determination of distance-protection performance

The paper examines the limitations imposed by power-system performance on the measuring accuracy of distance relays, and, from this, indentifies the significant power-system conditions which contribute to the maintenance of satisfactory discriminating margins. The performance requirements thus established are initially related to the characteristics of present schemes of protection, and, from the limiting conditions encountered there, alternative forms of protection characteristics are considered. The ultimate limits of multizone distance-protection application are, in this way, related to power-system requirements, to indicate those cases where the use of alternative forms of protection may be desirable. Other contributions dealing with other, more specialised, aspects of the problem are considered in the wider context of the problems discussed in the paper.