Design of phase and amplitude comparators for transmission line protection

This paper describes the design of poly-phase power system relays by using the amplitude and phase comparison techniques. Both techniques are used for designing phase-to-phase, three-phase and phase-to-ground relays. A new poly-phase amplitude method, which uses inputs from the phase comparator, is proposed for protecting power transmission lines during phase-to-phase and three-phase faults. A unique amplitude and phase comparison approach is introduced for use in a poly-phase phase-to-ground relaying unit. The proposed designs are suitable for implementation on microprocessors. Performance of the comparators was evaluated by using data simulated using EMTDC and some results are included in the paper.