Protection relay loop measurement analysis

High voltage transmission system availability and system security are key performance criteria for electricity utilities worldwide. System disturbances need to be cleared quickly and accurately in order to minimise the impact of faults and to facilitate speedy system restoration. It is therefore of paramount importance that protection relay performance is at its best. Protection relay performance analysis is normally done using the relay algorithms that represents the impedances measured in the so-called positive sequence domain. In the quest for best protection performance, this article will focus on the analysis of relay performance using a loop measurement analysis. This article aims to shown that with the loop domain method of relay operation analysis, a higher degree of accuracy pertaining to impedance relay operation and relay comparison can be made.