Study On Insulation Of 40.5kV Wall Bushing

The wall bushing is an important component for interconnecting the high-voltage electrical switchgear each other and also an effective guarantee for the stable operation of the entire power system.In the actual work process,due to unreasonable structural design or moisture,etc.,a non-uniform electric field appears in the wall bushing.If it is operated in such an electric field for a long period of time,the wall bushing will be aged,eventually leading to a reduction in the withstand voltage level and a decrease in the insulation performance.Therefore,it is necessary to analyze the insulation performance of the wall bushing.In this paper,an equivalent electric field model of a 40.5 kV wall bushing was developed.By the numerical simulation,theoretical calculation,and test methods,it was verified that the optimized wall bushing has a good electric field distribution and can effectively slow down the rate of electric aging.The research content of this article includes the following aspects:Firstly,an equivalent electric field calculation model of the wall bushing was established.Based on the established model,the formulae for electric fields calculation in multi-media were deduced to find relevant factors affecting the electric field distribution,such as the number of the umbrellaskirts,the length,radius,mesh and orientation of the inner and outer shielding layers.The calculation results provide references for SloidWorks modeling.Secondly,the three-dimensional models of different types of wall bushings were developed in SolidWorks,and then imported into the electric module of ANSYS software.The simulations of the shielded and unshielded wall bushings were carried out,respectively.The effects of the mesh,length,radius,and orientation of the inner and outer shield layers on the electric field distribution were investigated by the electrostatic field simulation.It was found that the inner and outer mesh layers can be replaced by the inner and outer meshless layers in the simulation process,and the inner and outer shielding layers oriented upwards and downwards can make the wall bushings have a good electric field distribution.When the length of the inner shielding layer is 170 mm,the length of the outer shielding layer is 2/5 of the length of the inner shielding layer(68mm),and the distance between the inner and outer shielding layers(the difference of the radius of the inner and outer shielding layers)is greater than 24 mm,the electric field distribution will be more even.Thirdly,the different voltage grade withstand voltage tests were conducted on the wall bushings after and before optimization,respectively.Through comparison,it was proved that the optimized wall bushings had a better electric field distribution.