Evaluation of frequency deviations effects on performance of digital protection relays

Abstract

Frequency deviations, which result from the changes in the dynamic balance between load and generation levels, are prime reasons of concern for power quality. The use of digital multifunction protective relays and their proper integration into power system is an important matter. However, the performance of digital relays depends on many factors and needs to be carefully evaluated. In this paper, the effects of frequency deviations on the operation and performance of multifunction digital distance relays are assessed and measured during laboratory tests in many conditions which show the weakness of relay with MHO settings to work properly during frequency deviation.