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Abstract—The paper presents the results of analysis of the geoelectric (telluric) field variability during the Earth's magnetic field disturbances, caused by extreme space weather events. The area of the study is the territory of the Yenisei-Khatanga Regional Trough (YKRT) situated in the auroral zone, where geomagnetic disturbances are characterized by a high level of intensity. The economic development of the YKRT as a large oil and gas-bearing area in the Russian Arctic increases the relevance of the study of possible negative impacts of space weather on future infrastructure facilities. The most serious threat to conductive industrial structures in the polar region will be posed by geomagnetically induced currents (GIC) driven by geoelectrical responses to rapid geomagnetic field changes. The analysis of the variability of telluric fields and calculations of their extreme values in the YKRT area were made using a unique magnetotelluric impedance tensor database collected by Nord West Ltd. as a result of the regional phase of the geophysical study of the trough and adjacent areas. The geoelectric field spatial-frequency distributions on the Earth's surface were calculated on the basis of the impedance estimates and harmonic approximations of the external geomagnetic excitation. The obtained maps were correlated with geological data to find areas characterized by maximal distortions of the telluric field. Extreme amplitudes of geoelectrical responses at a series of representative locations in the YKRT were evaluated on the time series of telluric field variations, synthesized through the impedance dependences on frequency and magnetic field time series recorded during geomagnetic storms and substorms at the nearest stationary monitoring sites. The resulting estimates of amplitudes and directions of geoelectric fields during space weather disturbances can be used to account for possible destructive effects of GIC in design of pipelines, power transmission lines and railways. [ABSTRACT FROM AUTHOR]

• 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. [ABSTRACT FROM AUTHOR]