Interference in the three-phase DC resistance tester can be eliminated by the following steps



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Three-phase DC resistance tester is a new generation of transformer DC resistance testing instrument. It can automatically select the test current according to different types of power transformers and display test results at a faster speed. It also has functions such as storage, printing, discharge indication, etc. With a built-in non-volatile memory, it can store measurement data for a long time. The adoption of a liquid crystal display gives the instrument a good human-machine interface. Therefore, this tester is an ideal device for DC resistance testing.


Due to the different manufacturers of three-phase DC resistance testers, the equipment produced has its own advantages and disadvantages, and some problems have occurred during use. There have been many cases where the unbalance of DC resistance on the low-voltage side exceeded the specified range, causing unnecessary hoisting inspections of transformers under normal conditions.


In order to ensure the accuracy and reliability of the measurement data of the three-phase DC resistance tester as much as possible, when measuring DC resistance, if an unbalanced phenomenon is found, you can first follow the steps below to eliminate interference, so as to avoid misjudgment and unnecessary losses.


1. First, check the test lead clamps. The elasticity and contact surface are good, and the test leads are not broken, eliminating the influence of test leads and test instruments.


2. Allow sufficient settling and discharge to eliminate the influence of residual charge or induced potential.


3. Switch the tap changer multiple times. If the unbalance rate does not decrease significantly and the DC resistance unbalance rate of each tap is similar, the influence of poor contact of the tap changer can basically be ruled out.


4. Perform temperature conversion to compare with the previous test.


5. Based on the data from the factory and handover reports, determine whether the DC resistance unbalance rate exceeding the standard is due to differences in lead resistance during manufacturing.


When analyzing data, relevant factors and criteria should be comprehensively considered. Do not simply apply the standard values from regulations. Instead, based on the ideas of the regulations and the specific conditions on site, analyze the development and change process of the equipment measurement data. In some cases, the winding tap voltage ratio test can effectively verify the tap-related positions and also check whether the connection group of the transformer winding is correct.


We hope the above content can help you better understand this tester.







Note: The above information and technical parameters are compiled and released by Yangzhou Dare Electric Co., Ltd.