Fault analysis of the 110 KV power grid with one-way power supply

•Combined internal overvoltage occurs as a result of the disturbances and failures development in the distribution electrical grids.•In power supply schemes for remote low-power consumers on long-distance lines, quasi-stationary voltage increases are possible due to the capacitive effect of long lines.•Quasi-stationary overvoltages can pose a danger to all substation equipment insulation, including power transformers, voltage transformers, non-linear surge arresters, etc.•Long-term currents exceeding the rated currents of power transformers can lead to power transformers thermal damage or the appearance of insulation defects.•In the event of a violation of the longitudinal symmetry of phase voltages, priority switching is not switching off the load, but disconnecting the network element on which the combined violation occurred. One of the main conditions for the non-development of quasi-stationary overvoltages is the operational work of personnel and the well-established operation of the relay protection. For consumers more than 100km away, this is not always possible to provide. This paper presents simulation-based studies on the 110 kV substations located in the Euro-Arctic region of Russia. Longitudinal and transversal disturbances in the high voltage grid are studied. The influence of the harsh climatic conditions on the rate of occurrence of accidents is shown. The 110-kV section of the Kola power system was considered and the features of this section were analyzed. The simulation model of the investigated section was created in the ATP-EMTP software and a wire break of the overhead transmission line followed by a single phase-to-ground faults of the same phase was simulated. The influence of combined overvoltage on substations electrical equipment is considered. The simulation results show that overvoltages in power grids with one-way power supply can pose a significant threat to insulation of any substation equipment.