Contents I. Introduction
Single-phase short-circuits represent the vast majority of disturbances occurring in high voltage power grids. Due to the fact that these power grids operate with a directly grounded neutral point, the values of single-phase short-circuit currents reach a significant level. In the event that a single-phase ground fault occurs at the substation, short-circuit current can cause a significant electric shock hazard [1], [2]. The part of ground current flowing into the substation grounding determines the hazard magnitude. All the conductive elements of objects located in the substation, neutral points of transformers and autotransformers, return conductors and power cable armors, also ground wires of overhead power lines, are connected to the grounding system. Tower grounding and adjacent grounding systems are also connected to the grounding system of substations via overhead ground wires [3], [4]. During a short-circuit to the ground fault in the substation, such an extensive system of connections causes all the above mentioned components to become a short-circuit current path.
