Impedance based fault location in power distribution systems

This thesis presents an investigation into impedance based fault location methods which directly use the fault transient as an excitation source to provide fast and accurate fault locations in small distribution systems such as the modem marine and aircraft power systems which have Integrated Power System (IPS) configuration. Fast and accurate fault location on un-exposed power distribution lines is of vital importance to expedite service restoration and improving the reliability of the power system. Two fault location algorithms are developed: the single-ended method and the double-ended method. The singled-ended algorithm which captures current and voltage waveforms from one end of the distribution cable estimates the fault locations using an iteration calculation. The double-ended method has a simple algorithm and is robust to different fault situations but requires additional data measured from the remote end of the cable. Both simulation and experimental tests have been done and the results are good enough to validate that the developed methods can locate fault positions using a 12ms window and otter an accuracy of within 1m in the proposed distribution system. The advantages and disadvantages of the proposed fault location methods are investigated under different fault situations. The possibility of employing the two methods in protection of faults in a marine power system is demonstrated. Due to the special characteristics of the marine power system, an active method which simply involves adding an IGBT switch is proposed for the earth fault protection.