| With the development of DC transmission projects and the improvement of transmission voltage levels,there are higher requirements for corresponding electrical equipment.In the use of DC bus surge arresters,zinc oxide surge arresters with multi-valve blade column parallel structure have been widely promoted due to their advantages of absorbing overvoltage energy and have become a key equipment for overvoltage protection in HVDC and UHV DC transmission systems.During the actual operation of the arrester,loss will occur when the overvoltage is absorbed.When the normal operating voltage of the line is withstand for a long time,the small current will cause a certain loss of the valve column.The existence of loss will cause the arrester to heat up and change the overall temperature.The temperature distribution and temperature rise affect the aging degree of the zinc oxide valve and the service life of the arrester.It is related to the safe operation of the entire power system.Therefore,the study of the time-varying temperature rise and temperature field distribution inside and throughout the multi-pillar arrester is of great significance to the thermal aging analysis of the arrester,the design of the heat dissipation structure,and the extension of the service life.At present,the research on the solution of the time-varying characteristics of the temperature field of the lightning arrester and the multiphysics is rare.Based on this,the main research contents of this article are as follows:Firstly,according to the actual size parameters,the three-dimensional geometric model of single section and multi column parallel DC arrester is built;according to the electric field theory and heat transfer theory,the mathematical model of electric thermal coupling simulation is built.By using the multi physical field coupling module of the finite element analysis software,the time-varying temperature field distribution of the whole single arrester and the general law of the temperature rise of different positions of the internal valve plate column are obtained.The feasibility of the coupling calculation method is verified by comparing with the actual operation experience and the temperature measurement experimental data.Secondly,on the basis of the electric-thermal coupling model,combined with the fluid mechanics theory,an electric-heat-current coupling calculation model is established,and a more complete multiphysics coupling calculation is carried out for the heating and cooling process of the single-section multi-column arrester.Comparing the calculation results with the electro-thermal coupling,it is shown that the calculation error can be reduced after considering the internal flow field.In order to further study the temperature characteristics of the target arrester,find out the time-varying law of temperature distribution and the change of the maximum temperature in different positions inside,the temperature field,flow field,air flow distribution and gas flow form of the top high temperature area are calculated and solved by using the coupled model.The relationship between the gas flow and the temperature distribution and temperature rise inside the arrester was found,and the sleeve and end of the multi-pillar arrester affected the distribution of the temperature field and the airflow field.Finally,according to the simulation results,the sleeve structure of the original geometric model is improved and the coupling calculation of the improved model is carried out.The feasibility of the improved sleeve structure is verified by the calculation results. |
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