844 / 2022-05-16 18:01:55

Simulation and actual measurement of the effect of series magnetization on the DC resistance test of converter transformers

DC resistance,,series magnetization,diagnostic test,conventional open-circuit,converter transformers

The measurement of the DC resistance of the valve side windings with bushings of the converter transformer is a diagnostic test that can effectively find out the poor connection between the valve side bushings and the valve side windings. For a long time, it has been limited by the valve side open circuit test conditions. This diagnostic test cannot be performed regularly.

In order to measure the DC resistance of the valve-side winding and bushing without disassembling the valve-side lead, this paper establishes a converter transformer model in the MATLAB environment that takes into account the saturation characteristics, and calculates the series magnetization and traditional open-circuit tests. In the wiring mode, the winding current, the remanence of the iron core and the transition characteristics of the on-load tap-changer are verified by a DC resistance tester on the actual commutation and transformation.

The calculation results show that under the condition that the valve side lead wire is not disassembled, the DC resistance obtained by using the series magnetization-assist wiring method is in good agreement with the DC resistance obtained by using the conventional open-circuit method. During the verification test, the difference between the test results of the two wiring methods was less than 0.5%. It is worth mentioning that, compared with the conventional open-circuit method, the DC resistance test time in the series magnetic-assist wiring method was reduced by 65%. Because two tests are required in the conventional open-circuit mode, only one test is required in the series-assist mode.

Compared with the conventional open-circuit method, the series magnetization method can take less time to complete the DC resistance test of the converter transformer winding and bushing without disassembling the valve side lead. This test method is helpful to guide the commutation Field testing of transformer DC resistance.