THE INFLUENCE OF PARAMETERS OF GEOELECTRIC FIELD AND ELECTRICAL POWER SUPPLY SYSTEM ON THE CURRENT AND VOLTAGE UNSINUSOIDALITY AT SUPPLY TERMINAL

The article describes cause-and-effect relation between geoinduced currents generation and current curves distortion and the voltage in electric power system. It was demonstrated that magnetizing circuit of power transformer is the source of higher harmonics of current and voltage on exposure of geoinduced currents to electric power system during geomagnetic storms. We give the results of computer modeling in the form of the current and voltage oscillographs, and line spectra of coefficients of the current and voltage harmonic components at the supply terminal, for two simulation models of electric power substations with “long” and “short” overhead power line of 110 kV when applying various power transformer load factors and geoelectric-field strength of 6 – 20 V/km. High-voltage synchronous electric motors are powered from the substations low-voltage buses of 6 kV.

It is demonstrated that the current and voltage unsinusoidality at the supply terminal are influenced greatly by electric power system parameters: for instance, the overhead lines length extension cause the amplification of higher harmonics of current and voltage. Geoelectric-field strength and varying of power transformer load factor affect the current and voltage unsinusoidality to a lesser degree. It is found that total voltage harmonics of low-voltage winding of a power transformer may exceed the values established by the standard GOST 32144-2013 for 6-25 kV supplies.