Auxiliary apparatus and method for fast testing DC resistance of large power transformer

Abstract

The invention discloses an auxiliary apparatus and method for fast testing the DC resistance of a large power transformer. The DC resistance testing is successively performed on an ab winding, an ac winding, and a bc winding. A test wire is not required to be changed in a test process such that test time is shortened and a test error possibly due to wire connection and disconnection is reduced. Two phases have same magnetic field direction and one phase has different magnetic field direction before and after wires are replaced such that the test time is shortened to a certain extent. The magnetomotive force generated on windings by the residual magnetism of a transformer is effectively eliminated and utilized by a short circuit manner. Thus, fast and simple demagnetization is achieved and residual magnetism with the direction the same as that in the next measurement is reserved. Thus, the charging time of the testing of the next winding is shortened and testing speed can be increased by low current. Single-chip microcomputer logic controls a relay to intelligently switch test terminals so as to change a test sequence.

Description

technical field [0001] The invention relates to a large-scale power transformer DC resistance quick test auxiliary device and a test method thereof. Background technique [0002] With the continuous increase of the capacity of the national grid, more and more large-capacity power transformers are connected to the grid, and the parameter testing work before the field transformer is put into operation is becoming more and more heavy, especially for large-capacity power transmission and transformation above 500kV. The DC resistance parameter test of a large power transformer, because its low-voltage side is connected in a delta manner, the windings cannot be opened, and the test time for measuring the DC resistance with constant current charging is very long, ranging from tens of minutes to a long time. Therefore, people use the method of increasing the test current and the capacity of the tester to speed up the test speed. The current is increased from 20A to 100A. The test sp...

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Problems solved by technology

[0002] With the continuous increase of the capacity of the national grid, more and more large-capacity power transformers are connected to the grid, and the parameter testing work before the field transformer is put into operation is becoming more and more heavy, especially for large-capacity power transmission and transformation above 500kV. The DC resistance parameter test of a large power transformer, because its low-voltage side is connected in a delta manner, the windings cannot be opened, and the test time for measuring the DC resistance with constant current charging is very long, ranging from tens of minutes to a long time. Therefore, people use the method of increasing the test current and the capacity of the tester to speed up the test speed. The current is increased from 20A to 100A. The test speed is indeed improved, but it is found that increasing the charging current will cause remanence in the iron core of the transformer. And the greater the charging current, the greater the residual magnetism of the iron core, and the influence of the residual magnetism of the transformer will cause the closing protection

Another method is to use the high-voltage magnetism test method, which is to connect the winding on the high-voltage side to the low-voltage side in series, and magnetize the iron core through the winding on the high-voltage side, so that the iron core can reach magnetic saturation quickly, and improve the DC of the low-voltage side winding. The purpose of resistance test speed, but the instrument with this function is very expensive, and the high-voltage side line must be connected when using it, so it cannot be operated when there is no crane or lifting platform on site, so find an instrument on site that can both It is very urgent to have a more convenient method for on-site wiring with a small current and to increase the test speed.

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