Field Analysis And Optimal Design Of Isolated-phase Enclosed Bus Of Combined Electrical Apparatus

Through the field analysis of the separated-phase closed busbar of the combined electrical appliance,the distribution and change law of the electromagnetic field and temperature field in the separated-phase closed busbar,as well as the influence of eddy current and temperature rise on the product performance,are provided a theoretical basis for the structural optimization design of the separated-phase closed busbar.This article takes the separated-phase enclosed bus in the ZF-252(L)/T4000-50 gas-insulated fully enclosed combined electrical appliance as the research object,and uses the finite element theory as the method to study the electromagnetic and temperature field of the separated-phase enclosed bus respectively,the corresponding mathematical model was established and an optimal design method was proposed.First,a mathematical model for electromagnetic field analysis of separated-phase enclosed busbars is established,and the electromagnetic field,induced circulation,eddy current loss,and electromotive force are analyzed and calculated.The ANSYS finite element simulation software is used to analyze the electromagnetic field of the busbar,and the distribution law of the electromagnetic field of the separated-phase closed busbar is obtained.The calculation results show that after a power-frequency AC current with rated value of 4000 A is applied to the three-phase bus with a phase angle lagging 120 degrees,due to the unbalanced resistance of the shell,electromagnetic induction produces a circulating current in the opposite direction to the bus current.It’s circulating current value is about 0.85 times of the bus current.At the same time,due to the electromagnetic shielding effect of the shell,the electric power received by the bus bar and the shell under the action of the power frequency steady state is very small,which can be ignored in engineering applications.Secondly,in order to study the loss and heating problem of separated-phase enclosed busbars,and the finite element method is used to establish the three-dimensional electromagnetic field-flow field-temperature field calculation model of the separated-phase enclosed busbar loss heating.The indirect coupling method is used to couple the eddy current loss into the flow field to calculate the temperature field of the isolated phase bus.The effects of fluid velocity,eddy current loss,convective heat dissipation and radiation heat dissipation are comprehensively analyzed,and the temperature distribution law of the isolated phase bus is obtained more accurately.The results show that the temperature of the bus conductor section is high at the top and low at the bottom,symmetrical left and right,and presents an S-shaped distribution.Since the B-phase bus has the worst heat dissipation capacity,the highest temperature appears at the top of the B-phase bus.The three-phase shell is blocked by the adjacent shell when radiating heat flow outwards,so the highest temperature in the shell appears at the position directly opposite to the adjacent shell.Through the calculation of heat dissipation and heat balance,it is verified that the isolated phase enclosed bus meets the heat dissipation requirements.Finally,through the temperature rise experiment of the research object connected with three-phase AC with rated value of 4400 A,the temperature rise test data are compared with the simulation results.The results show that in the calculation and analysis of finite element software,the temperature distribution of isolated phase enclosed bus has the same trend as the test results,and the error is within the allowable range,which verifies the accuracy of temperature field simulation.The response surface method and the finite element method are combined to optimize the design of the product’s structural parameters.The optimized parameters are re-established in the finite element analysis model,and a three-phase alternating current with a rated value of 4800 A is used for temperature field simulation calculations.The results show that the optimization method can reduce the temperature of the isolated phase enclosed bus of ZF-252 gas-insulated fully enclosed combined electrical appliance,and the error of the results is also within the acceptable range.The optimization design meets the national standards and product operation requirements,and improves the reliability of product operation.The test results are correct and have great application value.