A Correlation Method for Transmission Line Protection

A method of transmission line protection based on a distributed parameter model of the line is outlined. It is shown that the fault distance appears as a time delay between two quantities associated with the travelling waves at the measurement site. The time delay can be extracted from the fundamental voltage and current waveforms in the presence of superimposed line transients by means of a correlation technique. The proposed method has been tested by numerical simulations and by means of a real-time analog-type computer on a model transmission line and the results were found to be satisfactory. The feasability of a digital computer implementation is briefly discussed.