A positional polarity comparison relay utilizing global positioning system

This paper presents a new relay for the protection of power transmission systems by using the global positioning system (GPS) and the transient polarity comparison techniques, the positional polarity comparison relay. A specially designed protection relay detects the fault generated high frequency current transient signals and records the polarity of the transient signal and the time instant corresponding to when the initial travelling wave generated by the fault arrives at that busbar. A communication unit is used to transmit and receive coded digital signals of the local information to and from the associated relay(s) in the system. At each substation, the relays determine the location of the fault by comparing the polarity and the GPS time stamps measured locally with those received from the adjacent substations. Simulation studies presented in the paper demonstrate the feasibility of the scheme.