An improved setting-free power swing blocking scheme using local end information

摘要

A distance relay mal-operating during power swing has been very frequently attributed to triggering the events leading to a power system blackout. The existing methods rely on settings being proposed by the operators, which in turn are calculated from exhaustive offline simulation studies. Apart from being cumbersome, these methods are not adaptable to the changes in the power system. As such, the requirement of an algorithm to identify power swings based on local measurements and without settings cannot be emphasized enough. This paper examines the effectiveness of one such method to detect power swings based on continuous impedance measurements, and identifies the cases where the same is found to be lacking. Necessary modifications are suggested to make the algorithm overcome the identified shortcomings. The benefit of this method is that it employs a very simplistic approach in analyzing the locus of the impedance trajectory to identify power swings and the suggested improvements do not require any additional functional blocks to improve its effectiveness. The effectiveness of the suggested approach is validated on Western Systems Coordinating Council (WSCC) 9-bus system. The results show improved performance in terms of power swing identification over wide range of swing frequency.