The DC resistance test of power transformers is a more convenient and effective test for assessing the winding longitudinal insulation and current loop connection conditions among all the test items of the transformer. It can reflect the short circuit between winding turns, the broken strand of the winding, the contact state of the tap switch, the difference of the wire resistance and the joint contact and other defects.

The measurement of the DC resistance of the transformer winding can find some major defects in the loop, and the sensitivity and accuracy of the judgment are also high. However, the following relevant requirements should be followed in the field test to obtain an accurate diagnosis effect.

1) When measuring and analyzing the DC resistance of the transformer, its inductance is relatively large, and it must be charged in place to minimize the self-inductance effect. After the indicator pointer is basically stable, read the resistance value to improve the accuracy of the primary loop DC resistance measurement. Sex and accuracy.

2) The measured data should be compared horizontally and vertically, and the temperature, humidity, measuring instrument, measuring method, measuring process and measuring equipment should be analyzed.

3) When analyzing data, relevant factors and criteria must be considered comprehensively. The standard values of the regulations cannot be used alone, but the development and change process of the equipment measurement data must be analyzed in accordance with the ideas of the regulations and the specific conditions of the site.

4) According to the specific structure of the equipment, analyze the specific conditions inside the equipment, and measure the DC resistance according to different conditions to get the correct judgment conclusion.

5) Pay attention to the analysis, judgment and verification of comprehensive methods. For example, in some cases, the voltage ratio test of the winding tap can effectively verify the tap-related gear, and it can also verify whether the connection group of the transformer winding is correct.