METHOD OF CONTROL STARTING TRANSFORMER FOR POWER TRANSFORMER Russian patent published in 2018 - IPC H02M5/25 G05F1/30 

FIELD: electrical engineering.

SUBSTANCE: invention relates to electrical engineering, in particular to electric power systems. Power transformer is switched on and off when the load is powered by the rated voltage, which allows to reduce the power consumption in the dynamic operating modes of the substation and improve the harmonicity of the regulated voltage between the upper and lower limits. Method provides for regulating the voltage at the input of the power transformer relative to the mains voltage and to the consumers between the specified control limits. Method also provides for dividing the voltage regulation range into two sub-bands, upper and lower. When working between the upper and lower sub-ranges of voltage regulation, a deadband is introduced to change the conductive state of both the main thyristor keys and additional thyristor switches, at which the voltage deviations on the load do not exceed the permissible values both upward and downward from the nominal level. Switching off the power transformer of the substation without the occurrence of an electric arc and switching overvoltages is performed as follows. Before switching off the power transformer, pulses from additional thyristor switches are first removed. Then, the main thyristor switches are turned into a fully open state and the current is reset through the contacts of the three-phase contactor and the main reactor. Then, the three-phase contactor disconnects the de-energized main three-phase reactor without the occurrence of an electric arc and overvoltages. At the final operation of the method, the control pulses from the main thyristor switches with natural commutation are removed and they are switched off in a natural way without commutation losses. Expedient area of application of the proposed method is transformer substations of enterprises of all industries and agro-industrial complex with capacity from 0.4 to 2.5 MV⋅A with voltages of 35/(10–6) kV and (10–6)/0.4 kV.

EFFECT: method for controlling the starting transformer of a power transformer is proposed that improves the power characteristics of transformer substations by improving the sinusoidal voltage at the input of a power transformer and supplying it with an undervoltage at power on and off.

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