Estimation of geomagnetically induced currents in the Altai republic power system according to the Baygazan magnetic station data

A geoelectric field, voltages between grounding points of the Altai Republic power grid and geomagnetically induced currents (GIC) in power lines and grounding nodes were calculated in homogeneously conducting Earth's crust model with the resistivity of $5\cdot 10^2 Ohm\cdot m$ based on the magnetic station "Baygazan" data in the Russian Altai. These estimations have shown that the geoelectric field increased up to 30 mV/km, the potenthial difference between the power line grounding points reached value of 3.5 V and GIC value reached 0.12 A during the geomagnetic storm on August 5, 2023 (Kp=5–6) with geomagnetic field change rate increasing up to 10–15 nT/min. The GIC value in power line depends on the geoelectric field orientation. High rate of the north geomagnetic field component change causes GIC in latitude - oriented lines (Kosh-Agach – Inya, Ulagan – Inya, Ust-Koksa – Inya), high one for east component causes GIC in meridian - oriented line (Cherga – Inya). The resistancies asymmetry of the 'Ulagan – Inya' and 'Ust-Koksa – Inya' power lines causes an increase of GIC at Ininskaya substation grounding node with latitude-oriented geoelectric fields. The calculated data are compared with the results of monitoring of even harmonics amplitudes at the Ininskaya power substation. It is shown that the calculated value of the GIC in the grounded neutral of the power transformer at the Ininskaya substation correlates with the amplitude of even harmonics during the geomagnetic storm.