A method for demagnetizing a transformer core

Abstract

The invention discloses a transformer iron core demagnetization method, which is especially suitable for demagnetization of the iron core after the DC resistance test of the transformer; it is realized by applying pressure to the primary side winding of the transformer three times with a DC power supply; The duration is determined according to the collected primary current waveform; the first two pressurizations are carried out until the current of the primary winding of the transformer reaches the forward peak value and the reverse peak value, and the third pressurization time is the current from the forward peak value during the second pressurization. Half of the time required to reach 63.2% of the reverse peak value; the demagnetization of the iron core is completed through three pressurizations. This method greatly shortens the demagnetization time while ensuring the demagnetization effect, and the power of the demagnetization device is small, so it is practical.

Description

technical field [0001] The invention belongs to the technical field of transformer residual magnetism, and in particular relates to a transformer iron core demagnetization method. Background technique [0002] According to the requirements of the "Preventive Test Regulations for Electric Power Equipment", large transformers must be tested for DC resistance after maintenance or after 1 to 3 years of operation. The magnetic field generated by the DC current will leave a large amount of residual magnetism in the transformer core. When the transformer is switched on without load, affected by the residual magnetism of the iron core and the closing phase angle of the circuit breaker, the iron core may be saturated, resulting in a large inrush current of the transformer on the side of the sudden voltage change, resulting in a malfunction of the differential protection Tripping, causing the transformer to fail repeatedly in operation; a large value of the excitation inrush current w...

AI Technical Summary

Problems solved by technology

However, this method takes a long time to demagnetize, and it is easy to cause the hysteresis loop to shift during the process of changing the direction and size of the magnetic field, resulting in demagnetization failure, and sometimes even increases the remanence of the transformer.

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