Digital Distance Relaying

Increasing interest is being shown in the use of microprocessor for protection, switching and data acquisition required in modern high voltage substations. One of the most difficult functions to fulfill is that of transmission line distance protection employing samples of the voltage and current waveform taken from high voltage transducer equipment at the usual relaying point. This paper examines and compares different digital algorithms suitable for distance measurement, with particular reference to their accuracy and speed of calculation.