Impact Stress On Dielectric And Breakdown Properties Of Thermal Aging Insulator

Power transformer is the core equipment in power system,and the insulation state of oil-paper insulation directly affects the safe operation of transformer.The transformer in operation often appears load short circuit,short circuit electric force impact will cause winding deformation,and then cause serious damage to oil paper insulation structure.In order to evaluate the electrical damage caused by short-circuit impact stress on the insulation board of the transformer,the effect of thermal aging on the dielectric and polymerization degree and moisture content of the insulation board was studied.In this paper,the test plan,the test platform and the sample preparation are first made.A mechanical impact failure test device for simulating short-circuit electric force is designed and built.The thermal aging and mechanical impact failure schemes of the samples are formulated and treated with reference to a large number of relevant literatures.At the same time,design and manufacture the electrode device used in the penetration test.In order to study the effect of thermal aging on the dielectric parameters of oil-impregnated paperboard,thermal aging test was carried out in laboratory.The dielectric loss factor,relative dielectric constant,polymerization degree and moisture content were measured.On this basis,the impact stress on partial discharge and breakdown characteristics of oil-soaked paperboard after aging was studied.The results show that the dielectric loss factor and dielectric loss factor and relative dielectric constant,and increase the moisture content and degree of polymerization.The impact failure has obvious effect on the breakdown characteristics of the oil-soaked paperboard.With the increase of the impact stress failure strength,the initial voltage of the paper increases first,then decreases obviously,and then tends to be flat.With the increase of impact stress failure strength,the breakdown voltage of oil-soaked paperboard decreases and the dispersion of breakdown voltage has obvious cumulative effect.The relevant research in this paper can provide data reference for the design and manufacture of oil-paper insulation in transformer and the test and operation of HVDC transmission equipment.