A new power swing block in distance protection based on a microcomputer-principle and performance analysis

The authors present a new power swing block principle based on a microcomputer. This principle can reliably distinguish short circuits from swings, so that fast tripping is obtained for in-zone faults any time. The authors also analyse and calculate the performance of this principle in the case of different fault locations, fault resistance and power swing cycles. The program is incorporated into microprocessor based distance protection hardware, and tested on a power system dynamic model. The results are satisfactory. Distance protection with this power swing block has been installed on 220 kV transmission lines since 1986, and has achieved excellent performance