Digital Calculation of Impedance for Transmission Line Protection

The paper proposes a method of distance-type protection suitable for on-line digital computer protection of transmission lines. The basic principle is the predictive calculation of peak fault current and voltage from a small number of sample values. The magnitudes of various sources of error are discussed. The results of experimental work on a model transmission line and on a high- voltage transmission system are described. The calculation times for implementation in real time are estimated.