Preventive Tests for High-Voltage Test Transformers Can Be Conducted in the Following Aspects - Yangzhou Darui
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The purpose of measuring the DC resistance of transformer windings is to check the quality of winding joint welding and whether there are inter-turn short circuits; whether the contacts at each position of the voltage tap changer are good and whether the actual positions of the taps are consistent; whether the leads are broken, and whether multi-strand wires or parallel windings have broken strands. After a major overhaul, after changing tap positions, or after an outlet fault short circuit, it is necessary to measure the DC resistance of the windings together with the bushings.
Preventive tests for high-voltage test transformers can be conducted in the following aspects:
1. Measuring insulation resistance
A common and simple test method, usually measured with a megohmmeter. Based on the insulation resistance value measured at 1 minute, it can detect whether the insulation has through-type concentrated defects, overall dampness, or through-type dampness.
2. Measuring dielectric loss angle
As a highly sensitive test item, it can detect overall dampness, deterioration, aging of electrical equipment insulation, as well as local defects in small-volume tested equipment that are through or not through. However, when the tested equipment is large and the defect volume is relatively small, this method is difficult to detect. It is widely used in electrical manufacturing and in handover and preventive tests of electrical equipment.
3. Measuring leakage current
High-voltage test transformer has basically the same principle as measuring insulation resistance, and the nature of detected defects is also roughly the same. However, the power supply used in leakage current measurement is generally provided by high-voltage rectification equipment, and the leakage current is directly read with a microammeter. It has characteristics such as adjustable test voltage; high sensitivity, good measurement repeatability; conversion of insulation resistance value; and the ability to use the absorption ratio to judge insulation defects.
4. AC withstand voltage test
One of the destructive tests, it can further diagnose insulation defects in electrical equipment. The AC withstand voltage test is a strict, effective, and direct test method for identifying the insulation strength of electrical equipment. It can detect weaknesses in insulation during normal operation and plays a decisive role in determining whether electrical equipment can continue to be put into operation.
Note: The above information and technical parameters are compiled and released by Yangzhou Darui Electric Co., Ltd.
