Time-response polar characteristics of multisignal phase comparators in distance protection

Multisignal modes of phase comparison, as applied to distance protection, have been explored in recent papers in relation to the derivation of steady-state polar characteristics. However, no previous account has been devoted to the influence that the phase-comparator operating-time response has on this form of relaying, as is required in assessing relay performance under transient conditions. The purpose of the present paper is, therefore, to develop means by which time-dependent polar characteristics of multi-input phase comparators may be predetermined, and the protection operating time thereby related to defined characteristic shapes in the impedance axes. In orthodox 2-input relaying, it is frequently the practice to guard against transient overreaching in comparators during external faults by introducing a controlled increase in the comparator operating time as the boundary of protection operation is approached. This basis of overreach compensation is taken as a starting point in the present paper, and the variation of the dynamic characteristics with the time expended in comparison subsequent to fault onset is derived. As characteristics having directional features are, in addition, related to the form and level of polarisation used, the effect of polarisation on the dynamic characteristics is also investigated.