Detecting fault during power swing for a series compensated line

Abstract

The apparent impedance seen by a distance relay may fall within its operating zone during power swing. This may cause the relay to trip unnecessarily. To avoid unintended trip operation during such conditions, a power swing blocking function is utilized in distance relays. However, if a fault occurs during power swing, the relay should detect the fault and trip as soon as possible for maintaining security. Detection of fault during power swing in a series compensated line is more complicated due to the presence of protection circuit of the capacitor. This paper proposes a negative sequence current based technique for detecting fault during power swing in a series compensated line. The technique is tested for symmetrical and unsymmetrical faults in a system simulated through EMTDC/PSCAD. The method is compared with available techniques.