METHOD OF POWER TRANSFORMER NEUTRAL LINE RESISTIVE-THYRISTOR EARTHING Russian patent published in 2017 - IPC H01F27/34 

FIELD: electricity.

SUBSTANCE: invention relates to power engineering and can be used for power transformers protection of power plants and electric grids substations with rated voltage of 110 kV and above against geo-induced currents in geomagnetic activity periods at space weather perturbations. Method of power transformer neutral line resistive-thyristor earthing through thyristor switch consists in fact, that control pulses are supplied in absence of geomagnetic disturbances, thus providing thyristor switch continuous conductivity, and locked at occurrence of geomagnetic disturbances. To achieve technical result three thyristor keys are connected in-series, each of which is shunted with low-ohmic resistor, controlling geomagnetic field perturbation from by value of neutral line current constant component, and onset of magnetic system one-sided saturation is by occurrence of second harmonic in phase current, comparing neutral line current constant component value with scale of geo-induced currents fixed values corresponding to K_p – geomagnetic perturbation index values scale, and providing control pulses supply to all thyristor keys during periods of calm (K_p<2) and low-disturbing (K_p=2.3) geomagnetic field, and in case of phase current second harmonic exceeding permissible value locking control pulses supply to one thyristor switch in geomagnetic field disturbed state (K_p=4), on two thyristor switches with geomagnetic storm (K_p=5.6), to three thyristor switches with strong geomagnetic storm (K_p>7) and resuming control pulses supply to all thyristor storm after termination of geomagnetic disturbances.

EFFECT: expanding range of power transformers, protected against geo-induced currents, and limitation of reactive power losses at increase of geomagnetic disturbances intensity.

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