New technique for quadrilateral distance relay

A new technique for the development of a quadrilateral distance relay for transmission-line protection is reported. The modus operandi consists in continuously monitoring the coincidence period of four suitably derived relaying quantities, and the relay is made to develop trip output if the coincidence period is zero, whereas if the coincidence period is finite, the relay develops restraining output. Such a simple criterion results in extreme simplicity of the relay circuitry.