Method for computational determination of ground fault distance in an electrical power distribution network having a ring configuration

摘要

The present invention relates to a method for computational determination of ground fault distance in an electric power transmission network connected into a ring configuration utilizing the information available, e.g., from the numerical measurement data obtained by means of a multifunction protective relay. According to the method, the fault is detected and the faulted sending end (6) is identified, the fault resistance to ground is computed, and the faulted sending end (6) is connected to form a looped ring with one of the sound sending ends (5). According to the invention, the zero-sequence voltage, the line-to-neutral voltages and the zero-sequence currents of the sending ends connected into a looped ring are measured, plus one line-to-line voltage to obtain a phase reference for phasor synchronization, the looped ring is released after the measurements, the phases of the measurement signals are referenced to the line-to-line voltage and frequency components different from the fundamental frequency are filtered away, whereupon the RMS values of the signals are computed based on the thus obtained fundamental-frequency components of the signals, and the fault distance is computed, whereupon the faulted line section can be disconnected.