Frequency domain analysis applied to digital transmission line protection

The power system protection function dictates the character of the voltage and current signal processing required in the replacement of switching station instrumentation by digital computers. A complete signal processing technique is designed on the basis of a frequency domain analysis of the protection requirements, and such factors as analog filtering, data window size and sampling frequency are chosen by their frequency characteristícs. The processing technique is demonstrated by applying it to impedance measurement of staged faults. Sub-cycle fault detection is accomplished using an unsynchronized, nonsimultaneous sampling frequency of 240 Hz with simple RC analog filters.