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Distribution networks with a voltage of 35 kV are mostly used to supply electricity consumers located in rural areas. These networks, which mainly have overhead lines, normally function according to the radial principle, although in most cases they are closed or with two-way power. In recent years, the structure of 35 kV electric network has been changing, they are being transformed from aerial to aerial- cable due to the construction of 35 kV cable lines in rural areas, which in most cases are performed with cables with cross-linked polyethylene insulation.

One of the current issues in a complex electrical network with isolated (compensated) neutral is the selective identification of the damaged element during a single-phase-to-ground fault (SPGF). In order to achieve selective and reliable operation of protections against SPGFs in complex networks with isolated (compensated) neutral, besides information about the zero-sequence current and connection, information about phase voltages, zero-sequence voltage of the electrical network, and the operation of protection devices against adjacent SPGFs is necessary.

6–35 kV electrical networks operates with isolated or compensated neutrals. Such mode of a neutral is the reason of emergence of considerable overvoltage in an electrical network during single- phase ground fault (SFGF), especially during short-circuit through an arc and various ferro-resonance phenomena. These overvoltage destroy the insulation of the electrically coupled network.