The Influence of Geomagnetic Storms on Thermal Processes in the Tank of a Power Transformer

Modeling issues devoted to the thermal processes in the tank of five-legged core-type power transformers, when exposed to geomagnetically induced currents (GICs), were considered. The method of calculation of additional eddy current losses and temperature of the most heated point of a power transformer tank while flowing through grounded windings of GICs was developed. It was shown that recording heat-exchange processes-convection and irradiation-while GICs flow through grounded windings of the power transformer enables refining the temperature increase of the most heated point of the tank. The results of calculation of the additional losses on the coordinates on the tank walls and the temperature change rate in the most heated point of the five-legged core-type power transformer TDC-400000/242/20 tank during the heat exchange between the tank and air and oil depending on the value of GIC are presented. The dependencies of temperature increase in the most heated point of the transformers tank on the geoinduced currents of different values were calculated. The limit values of temperature increase were determined. The comparison of obtained values with their temperature limits set up in standard IEC 60076-7 are given.