The AC withstand voltage test is the most effective and direct method for evaluating the insulation strength of power equipment.  

During the operation of power equipment, insulation will gradually deteriorate due to the long-term effects of electric fields, temperature, and mechanical vibrations. This includes overall deterioration and partial deterioration, resulting in defects. For example, local defects may exist due to concentrated electric fields or fragile insulation in certain areas. Various preventive testing methods have their own strengths and can detect some defects separately, reflecting the insulation condition. However, the testing voltage of other testing methods is often lower than the working voltage of power equipment, and as a guarantee for safe operation, it is not strong enough. Although the DC withstand voltage test has a relatively high test voltage and can detect some weak points in insulation, due to the fact that most insulation of power equipment is composed of composite dielectrics, the voltage is distributed according to resistance under the action of DC voltage. Therefore, the weak points of AC power equipment under AC electric field may not be detected when tested with DC, such as slot defects in generators that are difficult to detect under DC. The AC withstand voltage test conforms to the electrical conditions that power equipment can withstand during operation. At the same time, the AC withstand voltage test voltage is generally higher than the operating voltage. Therefore, after passing the test, the equipment has a large safety margin. Therefore, this test has become an important means to ensure safe operation.  

However, due to the fact that the test voltage used in the AC withstand voltage test is much higher than the operating voltage, excessively high voltage can increase insulation medium loss, heat generation, discharge, and accelerate the development of insulation defects. Therefore, in a sense, the AC withstand voltage test is a destructive test.  

Before conducting the AC withstand voltage test, various non-destructive tests must be carried out in advance, such as measuring insulation resistance, absorption ratio, dielectric loss factor (tg ¢), DC leakage current, etc. The results of each test must be comprehensively analyzed to determine whether the equipment is damp or has defects. If any existing problems are found, they need to be dealt with in advance. After the defects are eliminated, the AC withstand voltage test can be carried out to avoid insulation breakdown, expansion of insulation defects, extension of maintenance time, and increase in maintenance workload during the AC withstand voltage test process.

The relevant high-voltage testing equipment for Wuhan UHV production mainly includes series resonance systems, CVT inspection resonant boosting devices, AC voltage withstand resonance devices for substation electrical equipment, portable cable voltage withstand test devices, generator AC voltage withstand resonance devices, SBF triple frequency transformers, GTB series dry-type test transformers, YDJ series oil immersed test transformers, YDQ series inflatable test transformers, fully automatic anti-interference abnormal frequency dielectric loss testers, BC2000 intelligent dual display insulation resistance testers, HT2671 digital megohmmeters, etc.