Study On The Effect Of Repair On The Inter-turn Insulation Index Decay Oscillation Voltage Withstand Characteristics Of Dry-type Air-core Reactor

Dry-type air-core reactors are widely used in power systems and insulation cracking is one of the causes of their failure.The exponential decay oscillation voltage is the main factor of insulation deterioration in the operating cycle of dry-type air-core reactors.Firstly,the basic electrical properties of epoxy resin,insulation repair material(epoxy acrylate)and the effect of insulation repair on breakdown field strength of cracked epoxy resin were studied,and electrical performance parameters such as breakdown field strength and volume resistivity were measured.The test results showed that there were some differences in the bulk conductivity,relative permittivity,and dielectric loss between the insulation repair material(epoxy acrylate)and epoxy resin,but the differences in breakdown field strength was not significant.The effect of repair on the model specimens of inter-turn insulation was further investigated,and the ability of the specimens before and after repair to withstand the short-time industrial frequency breakdown voltage and the cumulative effect of exponential decay oscillation voltage was measured.The test results show that the cracking will significantly reduce the short-time frequency breakdown and the ability to withstand the cumulative effect of overvoltage on the inter-turn insulation,and the insulation repair has a good effect on the improvement of the performance of the cracked inter-turn insulation.Then the effect of moisture on the inter-turn insulation specimens within the package was studied,and the ability of the specimens before and after moisture to withstand the cumulative effect of exponential decay oscillation voltage was measured in terms of frequency breakdown voltage and tolerance.The test results show that the effect of package cracking on the inter-turn insulation characteristics inside the package in a dry environment is not significant,but package cracking in a humid environment leads to a significant reduction in the inter-turn insulation characteristics inside the package,and insulation repair can improve its inter-turn insulation performance.To quantify the effect of restoration on the electrical aging life of the inter-turn insulation under exponentially decaying oscillation voltage,accelerated electrical aging tests were conducted on model specimens before and after restoration,respectively.The results show that the repair can significantly improve the electric aging life of the dry-type air-core reactor inter-turn insulation.Through the analysis,it is found that the electric aging life of inter-turn insulation does not conform to inverse power model,which is modified,and the modified electric aging equation is more consistent with the actual situation.The research in this thesis can provide theoretical support for whether to conduct insulation repair on dry-type air-core reactor,and then improve the operational reliability and safety of dry-type air-core reactor.