Identification of High-Impedance Earth Faults in Neutral Isolated or Compensated MV Networks

This paper introduces novel methods for the identification and location of very high impedance one phase-to-earth faults in medium-voltage (MV) networks in order to improve the electrical safety and reduce the number and duration of outages to customers. The examination is restricted to neutral compensated and isolated MV systems which are the prevailing neutral treatment practices in Europe. The main target of the study was the development of the new method for the identification and location of earth faults up to very high fault resistances. The method is technically applicable in actual use because it utilizes standard measurements available at all 110/20 kV primary substations. No new measuring instruments or devices are needed. The major algorithm is based on the calculation of the fault resistance for every MV feeder. Field experiments in real networks have also been conducted for testing the methods. The indication method presented can identify and locate faults approximately up to 100–200 k $\Omega$.