Study On Contact Degradation And Flow Capacity Evaluation Of GIS Disconnector

The load capacity of GIS disconnector which as the series equipment in power system,is an important safety and performance indicators.The load capacity of GIS disconnector directly affects the safe and stable operation and the size of the upgrading of the whole power network,its overload will lead to overheating,reduce the mechanical strength of the metal and accelerate the aging of the insulation and the stress relaxation of the metal,even when serious burned equipment cause short circuit fault which cause the accident of large area blackout,resulting in significant economic losses,and bringing adverse social impact.Thus research on contact degradation and load capacity evaluation of GIS disconnector is helpful to improve the reliability of the electrical connection and load capacity,and provide security for the safe and stable operation of power grid.Combined with the sub project of National high technology research and development program(863 Program),based on the stress relaxation phenomenon and the basic electrical contact parameters(electrical,mechanical and thermal properties)of GIS disconnector,the research on the contact degradation and load capacity evaluation of GIS disconnector is carried out in the following aspects:The phenomenon of stress relaxation is the main form of failure of elastic elements(holding spring),the failure of the spring will result in the decrease of the contact pressure of GIS disconnector,which will lead to the contact degradation and temperature rise.Therefore,the force analysis of GIS disconnector plug-in connecters has been carried out in this paper,the finite element numerical simulation model of GIS disconnector holding spring has been established,and has studied on its nonlinear stress relaxation behavior under different temperature,which laid the foundation for the resarch of contact characteristics and temperature characteristics of GIS disconnector;Temperature rise is an important index to check whether the GIS disconnector is running well or not and test the load capacity.Thus based on the analysis of the electrical contact theory and the multi-field coupling phenomenon of GIS disconnector plug-in connecters,equivalent model of conducting bridge and electrical-thermal-structucal coupling model of GIS disconnector plug-in connecters to calculate the temperature rise have been established;The electric field,temperature field and stress field distribution characteristics of GIS disconnector plug-in connecters under normal operating conditions have been analyzed,the calculation results of the temperature rise of GIS disconnector plug-in connecters have been compared with the test results with different current,and the validity of the numerical model has been verified,which laid the foundation for the resarch of contact degradation and load capacity evaluation of GIS disconnector;Based on three dimensional finite element numerical calculation model of electrical-thermal-structucal coupling of GIS disconnector plug-in connecters,the influence of the factors such as the change of temperature,the load current,the contact resistance and the closing of the switch on the temperature rise of the GIS disconnector has been analyzed;The interaction between stress relaxation,contact resistance,temperature and load capacity has been studied,according to the maximum allowable operating temperature of contact conductors shall not exceed 105 ℃ with the 40 ℃ ambient temperature,and combined with the stress relaxation and temperature rise characteristics of GIS disconnector,the relationship between contact resistance and load capacity of GIS disconnector has been obtained by the simulation model of temperature rise,then the contact degradation process and load capacity of GIS disconnector with different initial contact resistance under different load current have been studied,which provides theoretical guidance and technical support for dynamic compatibilization technology of power system.