Voltage analysis of high resistance earthed fault in non-solidly grounded systems

It is difficult to select the faulty feeder when a high resistance earthed fault happened in non-solidly grounded systems. In the paper inversion transform theory is employed to analyze and discuss the voltage vector characteristics so as to provide the evidence for clearing faulty feeder when a high resistance earthed fault happened. Based on the analysis, we get the following conclusions: the phase voltage of healthy feeder is higher than line voltage; the voltage amplitude of two healthy feeders is unequal; the phase voltage of healthy feeder is even lower than that of the faulty feeder in some cases which is essentially different from the case of zero and lower resistance grounding faults. With the application of obtained voltage characteristics of single-phase high resistance earthed fault, the sensitivity and reliability of the currently used faulty feeder selection equipments will be greatly improved.