In the operation of power equipment, the insulation will gradually deteriorate under the action of electric field, temperature and mechanical vibration for a long time. Including overall metamorphism and local metamorphism, forming defects. For example, there are local defects due to local electric field concentration or local insulation fragility. All kinds of preventive test methods have their own advantages, and they can find some defects and reflect the insulation condition, but the test voltage of other test methods is often lower than the working voltage of power equipment, which is not strong enough as a guarantee for safe operation. DC withstand voltage test Although the test voltage is relatively high, some insulation weaknesses can be found, but because the insulation of power equipment is mostly composed of dielectrics, under the action of DC voltage, its voltage is distributed according to resistance, so the weaknesses of AC power equipment can not be found in DC test, for example, the slot defect of generator is not easy to find under DC. Ac withstand voltage test conforms to the electrical condition of power equipment in operation, and the voltage of AC withstand voltage test is generally higher than the operating voltage, so the equipment has a large safety margin after passing the test, so the test has become an important means to ensure safe operation.
However, the AC withstand voltage test is much higher than the operating voltage, which will increase the loss, heat and discharge of insulation medium and accelerate the development of insulation defects. Therefore, in a sense, AC withstand voltage test is a destructive test.
Before AC withstand voltage test, various nondestructive tests must be carried out in advance, such as measuring insulation resistance, absorption ratio and dielectric loss factor tg? And DC leakage current. Comprehensive analysis of the test results to determine whether the equipment is damp or defective. If the existing problems are found, they need to be dealt with in advance, and the AC withstand voltage test can only be carried out after the defects are eliminated, so as to avoid insulation breakdown and insulation defects expanding during the AC withstand voltage test, prolong the maintenance time and increase the maintenance workload.
The related high-voltage test equipment produced by Wuhan Huatian Electric Power Company mainly includes BPXZ series resonance system, XZB-H CVT test resonant booster, AC withstand voltage resonance device for substation electrical equipment, BPXZ-HT portable cable withstand voltage test device, TFL-HT generator AC withstand voltage resonance device, SBF tri-frequency transformer, GTB series dry test transformer, YDJ series oil-immersed test transformer, YDQ series inflatable test transformer and HTJS-V full-automatic anti-interference different frequency transformer.