Determination of Earth Faults in Cable Lines with Insulated Neutrals

The most frequently damaged elements of the electric grid are power lines. Depending on the type of damages in the lines they can be single-phase and multiphase. Since the most frequent types of damages are single-phase SC (short circuits), it is their determination that is in priority. In medium-voltage grids operating with insulated neutrals, single-phase SC is not short-circuit. Also, for overhead lines more than 90% of damages belong to the most common damages and cannot be eliminated by themselves. Single-phase SCs develop into multiphase short-circuits, causes emergency tripping, so the search for single phase-to-earth fault in cable lines should be carried out immediately after their occurrence.