Adaptive out-of-step protection schemes based on synchrophasors

Adaptive out-of-step protection for multi-machine system using wide area measurements was studied in this paper. Two schemes were developed to detect the out-of-step condition. One is based on the real time swing curves directly, and the other on real-time extended equal area criteria. Both of them require identifying the groups of coherent generators, so a fast online coherency identification technique suitable for online applications was also developed. These two schemes are intended to be applied in the system control centers since they require wide area measurement. The developed schemes were tested on a 127-bus system. Compared with those methods based on assumed system conditions and indirect information, the proposed schemes in this paper are more reliable since they adapt to the prevailing system conditions.