Failure Mechanism Study Of Gas Insulated Bus Contact Based On Theory Of Friction And Wear

Plug-in contacts are often used in Gas Insulated Bus to connect conductors at different intervals.The contact of Gas Insulated Bus generally works under the environment of large current and non-air medium,and there is a process of friction and wear on the contact under the cyclic load caused by the change of daily load current and ambient temperature.In this case,the contact resistance increases and the contact temperature rises,making the contact become a weak link in the operation of equipment.The overheating fault of Gas Insulated Bus caused by contact failure often occurs,which seriously endangers the safe and stable operation of equipment and power system.In this paper,aiming at the contact failure process and failure mechanism of gas-insulated bus contacts in non-air medium,the contact failure mechanism of Gas Insulated Bus was analyzed by establishing the contact model of rough surface and friction and wear model,carrying current friction and wear physical test and contact failure mechanism analysis.In order to analyze contact failure mechanism through friction and wear theory,it is necessary to first learn relevant theories of electrical contact.In this paper,the microstructure and evaluation index of the contact surface and the elastic-plastic deformation theory based on the contact area under the action of co ntact pressure are introduced.Bahrami model is proposed to analyze the number and radius distribution of contact spots in the apparent contact area of contact points of Gas Insulated Bus contacts,and then the contact resistance is solved.According to the characteristics of friction and wear process of Gas Insulated Bus contacts,the wear stages,wear models and wear modes in friction and wear theory are studied,which provides a theoretical basis for failure mechanism analysis of Gas Insulated Bus contacts.In order to study the failure mechanism of Gas Insulated Bus contacts,it is necessary to study the electrical contact characteristics of Gas Insulated Bus contacts.Based on the basic structure and operation characteristics of the Gas Insulated Bus contact,a simplified model of the Gas Insulated Bus contact was established to study the friction and wear of the single finger.Then,the change of contact resistance of contact points of Gas Insulated Bus contacts under different contact pressures was tested and compared with the Bahrami model to verify the effectiveness of the Bahrami model.Then,the contact resistance of contact points of Gas Insulated Bus contacts under different contact pressures was tested and compared with the Bahrami model to verify the effectiveness of the Bahrami model.Gas Insulated Bus is studied contact characteristics of contact,including:the normal service condition provided by the spring contact pressure size,the working current when the contact is running for a long time without failure and the uneven distribution of contact resistance under the influence of assembly and gravity.The friction and wear of the contact will increase the contact resistance and eventually lead to failure.It is explained that the relative sliding between the contact and the guide rod is due to the circulating thermal load and short circuit impulse current.Finally,the failure threshold of the contact is calculated according to the improved V-T relation,which is used as the judgment basis of failure in the subsequent research.In order to study the friction and wear process of contact current-carrying of Gas Insulated Bus,this paper built a friction test platform for contact current-carrying of Gas Insulated Bus according to the operating environment and conditions of contact.The platform uses sealed containers provide Gas Insulated Bus seal gas environment,with the reciprocating displacement in the motor driver to provide friction test,through the pressure control device to control the pressure test load,using Labview software acquisition contact resistance and temperature rise.In order to study the friction surface,three methods,surface topography analysis,chemical composition analysis and surface profile analysis,were used to explore the failure mechanism.In order to explore the contact failure mechanism of Gas Insulated Bus contact and study the influence of different factors on its contact,this paper carried out a control test on different gas media,different contact pre ssures and different current-carrying sizes.Through the analysis of contact resistance data,the contact failure law was summarized.Through the surface topography analysis,chemical composition analysis and surface profile analysis of the tested samples,the contact failure mechanism was explored.It is found that the type of gas medium,the contact pressure and the current load are the important factors that affect the contact failure of Gas Insulated Bus.In N₂ and SF₆,the contact state of the contact is basically affected by the degree of surface wear,but not by chemical reaction,and the failure process is slow.The increase of contact pressure will lead to the aggravation of surface wear,but after the silver coating is worn,the contact resistance is determined by the contact pressure.The greater the contact pressure,the smaller the contact resistance.The main effect of current on electrical contact is that it will increase wear and tear,while the temperature rise caused by large current will so ften the metal,thus increasing the contact area and slowing down the failure of the contact.The research content of this paper comes from the project of national natural science foundation of C hina（Research on multi-element dynamic degradation mechanism and failure prediction of Gas Insulated Bus contacts,project no.51607124）.Research by gas insulated busbar contact load flow friction and wear process and the contact failure result analysis,to improve the current,not under the air medium electrical contact theory,at the same time can provide gas insulated busbar equipment design,installation and condition monitoring provides theoretical basis and technical support,has important significance in theory research and engineering application value.