METHOD FOR MONITORING GEO-INDUCED CURRENT IN THE NEUTRAL OF POWER TRANSFORMER AND FOR CONTROLLING THE GROUNDING MODE Russian patent published in 2023 - IPC H02H9/02 

FIELD: electrical engineering; electric power industry.

SUBSTANCE: invention can be used to protect power transformers of power stations and substations of electrical networks with a rated voltage of 110 kV and above from the effects of geoinduced currents during periods of geomagnetic disturbances. A method for monitoring geo-induced current in the neutral of a power transformer and controlling the grounding mode through a parallel-connected current-limiting resistor and a thyristor key with two-position hysteresis control of on-off states, which consists in providing the initial ON state of the thyristor key by supplying control pulses, controlling the current neutral with a current Hall sensor, whereas the appearance of a geo-induced current is detected by a low-pass filter, the sixth harmonic of the magnetization current by a band-pass filter, and the supply of control pulses is stopped by turning the thyristor key into the OFF state. The control pulse blocking threshold is selected according to the criterion of the increase in the geoinduced current and the sixth harmonic of the magnetization current to the amplitude of the nominal no-load current of the power transformer and the OFF state of the thyristor key is maintained for a predetermined time interval of at least (3-4) periods of change of the slowest frequency component (f=0.001 Hz) of the geoinduced current, whereas the magnetization power of the power transformer is calculated by scaling the geoinduced current, subject the analog signals of the geoinduced current and magnetization power to a voltage-frequency conversion into two pulse sequences, one with a repetition rate pulses proportional to the magnitude of the geoinduced current, the other with a pulse repetition rate proportional to the magnitude of the magnetization power, and through the current loop interfaces, the logic signal of the neutral grounding mode of the power transformer is transmitted to the control room continuously, and the pulse signals of the geoinduced current and magnetization power only are transmitted in the state OFF thyristor key.

EFFECT: expansion of functionality by ensuring the stability of the neutral resistive grounding mode and instrumental support for making reasonable dispatching decisions to adjust the operating mode of the power transformer in conditions of significant variations in the intensity of geomagnetic disturbances.

1 cl, 5 dwg