Ultra-low frequency alternating-current (AC) constant-current demagnetization device of large transformer or mutual inductor and demagnetization detection method

Abstract

The invention relates to an ultra-low frequency alternating-current (AC) constant-current demagnetization device of a large transformer or mutual inductor, comprising a display (1) and a CPU control unit (2), wherein the CPU control unit (2) is connected with a power-frequency signal generator (3); the power-frequency signal generator (3) is connected with a voltage power amplifier (4); the voltage power amplifier (4) is connected with a voltage booster (5); the CPU control unit (2) is also connected with an ultra-low frequency signal generator (6); a switch is arranged between a transformer or a mutual inductor (8) to be tested and the voltage booster (5); and a switch is arranged between the transformer or the mutual inductor (8) to be tested and a current power amplifier (7). The invention overcomes the defects of long demagnetization time, easy transformer coil deformation, and the like of the traditional method and has the advantages of short demagnetization time, light equipmentweight, and the like. The invention also discloses a demagnetization detection method adopting the demagnetization device.

Description

technical field [0001] The invention relates to an ultra-low frequency AC constant current demagnetization device for a large transformer or transformer, and also relates to a demagnetization detection method using the demagnetization device. Background technique [0002] Transformer or transformer is an important equipment in the power system. Its safety and stability are very important to the operation of the entire power system. During steady-state operation, the excitation current of the transformer is only 1% to 2% of its rated current. However, when the transformer is switched on again after the DC resistance test, a large inrush current will be generated. Its peak value can be tens to hundreds of times of the rated current. If the residual magnetism of the transformer is large, the decay of this transient current is relatively slow, and it generally lasts for several seconds to tens of seconds before reaching a steady state. This is extremely unfavorable to the opera...

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Problems solved by technology

The demagnetization process of this method is not easy to keep consistent, and the measured magnetization curve has a large difference in the initial part

At present, the AC demagnetization method under power frequency is still widely used, but this method takes a long time, the equipment is huge, and the operation is also very complicated.

After the DC test, the electric power department generally demagnetizes by directly applying power or adopting a resonance test method. This method takes a long time to demagnetize, about 7-8 hours, and it is easy to cause the relevant relay protection action of the transformer. At the same time, direct closing will cause Powerful surge impact will cause deformation of transformer winding, etc., which will affect the life of transformer

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