Research On Action And Thermal Characteristics Of Pressure Controlled Varistor Device Used For Current Transfer

As China's economy gains momentum,power industry enjoys fast development with the electricity consumption by corporate and household soaring.High demand of electricity is bound to bring more pressure to the grid.Then the fault current caused by malfunction may have serious or even the irreversible impact on the entire electricity supply network.Current transfer utilizes voltage competition between parallel branches.The fault current is transferred from the main current branch to the functional branch parallel to it.Mainly used in fault current limiting and DC transfer breaking.In order to meet the requirements of rapid current transfer,this paper studies a device whose resistance is changed by pressure.Through controlling the change of pressure of the pressure-controlled material,we can control the resistance change.According to the principle of current transfer,we can note that the pressure-controlled variable resistance device need a steady access to the current loop with small on-state resistance,a strong electric current flow capability,and a good heat dissipation ability.Furthermore,it also should be able to swiftly increase branch impedance when a current fault occurs.This paper studies pressure-controlled rheostat,including its pressure output,separation speed and other characteristics affecting factors.At the same time to ensure that it is in the long-term stable state under pressure,we conducted a simulation study of the current.The influence of different materials and different heat dissipation methods on temperature changes is analyzed.In this paper,I design the pressure-controlled variable resistance device,and I also devise its operating mechanism and examine its operating characteristics based on this mechanism so that it can possess features like small volume,large pressure output,short opening time,small control current.The closing pressure of the variable resistance mechanism is designed to reach more than 12000 N.Ansoft was used to carry out finite element simulation and quantitative analysis of factors which affect its characteristics.Realize pressure control material resistance changes from milliohm level to ohm level within 5 ms.In line with the results from simulation and experiment,the pressure-controlled variable resistance device is blessed with a better pressure output and operation capability.Based on the laws of thermodynamics,Pressure-controlled material is connected to the circuit,the purpose is to analyze their steady state and transient state of fever through Ansys,which steady state passing current is greater than 500 A.Besides,the simulation comparison of the different materials,different thermal properties and insulation capacity was also launched and this paper also look into the effectiveness and feasibility of the various heat sink structures and cooling methods.On the basis of simulation analysis,the prototype machine of pressure-controlled variable resistance device is designed and assembled,and the resistance change characteristics of pressure controlled materials under the operating characteristics of the whole machine are measured and analyzed,and the current transfer dynamic test and through-current temperature rise test are carried out.The test and simulation results show that the pressure-controlled rheostat device has good operating characteristics and stability of branch resistance variation.It has the advantages of flexible control,short recovery time,easy closing operation,small volume and relatively low cost.It can quickly achieve current transfer through changes in resistance,improved current transfer efficiency.