Research On Fretting Wear Of Large Transformer Coil Insulation

With the continuous improvement of people’s quality of life,electricity has become one of the indispensable resources of today’s society.Therefore,the power industry has become an important development target that cannot be ignored by various countries.The construction of the “Belt and Road” not only drives the economic development of African countries,but also the construction of ecological power plants and power stations,alleviating the situation of local power supply shortages.Power supply capability provides a strong guarantee.The transformer is the core component of each power transmission and transformation system.Once the transformer is short-circuited,the transformer’s self-protection device will automatically power off,causing the transformer to be in a closed state,resulting in the failure of the entire power transmission and transformation system.Under normal circumstances,the short circuit of the voltage transformer is caused by the damage of the internal winding of the transformer.The excessive electromagnetic force or impact force generated between the transformer windings causes the internal structure of the winding to change,which causes damage to the insulating oil paper outside the coil,which in turn causes the transformer.Short circuit.Therefore,this paper has done an in-depth study on the cumulative damage effect of the transformer coil insulation layer.Firstly,the working principle and actual working state of the transformer are expounded,and the generation of mechanical force in the transformer is analyzed.Secondly,in order to study the influence of the axial mechanical force and impact force generated by the large-scale transformer on the opening and closing of the switch and the sudden change of the current on the coil insulation layer,the hydraulic servo fatigue tester was used to simulate the multiple opening of the brake.The fatigue test of the contact between the winding and the insulating pad under the action of closing and current mutation is carried out.The experiment changes the size,frequency and number of cycles of the load,and then observes the damage of the insulating layer under different cyclic mechanical force characteristics of the coil insulation paper.It can be seen from the experimental results that the number of damaged layers of the coil insulation paper is related to the frequency,the amplitude of the alternating load and the number of cycles.When the amplitude of the alternatingload is constant,the damage of the insulating paper is inversely proportional to the frequency;when the frequency is constant,the number of broken layers of the insulating paper increases as the amplitude of the alternating load increases;as the number of cycles increases,the number of cycles increases..In addition,the breakage of the insulating paper is spread from the inside to the outside,and the innermost layer of the insulating paper is most damaged.Under the action of the cyclic axial mechanical force,the internal embedding lines between the transposition guides are misaligned with each other.The accumulated misalignment will cause the outer insulating paper wrapped around the enameled wire to undergo tensile action.This stretching action will be through the insulating paper which is tightly wound with each other.Passed inside and out.However,under the action of static friction,the tensile effect of the insulating paper is gradually weakened during the transfer from the inside to the outside,so the outer layer of the outer insulating paper is less damaged.Finally,the finite element method is used to simulate and analyze the transformer coil,and different load conditions are set to obtain the stress and deformation of the transformer coil insulation paper under different conditions.Through the analysis of the stress and strain cloud map,the transformer coil is obtained.The insulation paper is most likely to be broken into the edge of the coil and the damage of the insulation paper under different loads and frequencies.