New high-speed microprocessor distance relaying for transmission lines

The paper discusses phase comparators, magnitude comparators and their applications in the design of a new high-speed microprocessor distance relay. Regarding ground distance units and phase-to-phase distance units, the torque created by a phase comparator or a magnitude comparator is described in terms of fault impedance and source impedance ratios. Both phasor- and time-domain approaches for computing torque are described. Different methods are presented for the designs of post-filters, which are utilized to ensure speed and security of the high-speed distance relay. Finally, typical test results of the distance relay tested on a model power system and digital fault recorder data from the relay are presented