Research And Improvement Of Electric Field And Temperature Field Characteristics Of 40.5kv High Voltage Switchgear

With the development of science and technology,switchgear is developing towards miniaturization,denseness,modularization,intellectualization,simple operation and high reliability.During the miniaturization and denseness of the switchgear,insulation and heat dissipation have become the key problems that restrict the development of the switch cabinet,and the insulation breakdown and fire occur in the switchgear.Therefore,the research on insulation and heat generation of switchgear has important practical value and significance.On the basis of consulting domestic and foreign literatures,I have studied the overall structure and performance characteristics of 40.5kV high voltage switchgear.Based on the GB-T11022-2011 requirements,the critical breakdown field strength of SF6 gas in a slightly uneven electric field is calculated,which is the required electric field value for insulation.The finite element method is used to simulate the electric field of the isolated switch chamber and the circuit breaker room of the high voltage switchgear.The results shows that the maximum field intensity in the isolation switch room and the circuit breaker room all appear on the edge of the top of the gas chamber,and the maximum electric field strength is greater than the electric field value of the insulation requirement.The whole structure of the vacuum interrupter and the key area of the design of the arc extinguishing chamber are studied.The electric field analysis of the vacuum interrupter is carried out with the vacuum breakdown field strength as the standard.The conclusion shows that the maximum electric field intensity of the vacuum interrupter is less than the critical breakdown field intensity of the vacuum,and the distribution of the electric field in the key area is very uneven.According to the key area structure and the key area insulation mechanism of the vacuum interrupter,the structure of a certain section of ceramic and shield in the arc extinguishing chamber is studied,and the influence of the size change of the arc extinguishing chamber on the electric field intensity in the key area is explored.The results show that the electric field concentration at the end of the screen is disappearing after the end of the shield is added to the end of the shield,and the strength of the electric field in the three heavy bonding point can be reduced by increasing the size of the short half axis of the pressure ring and the distance of the pressure ring to the ceramic shell,and the distance between the shielding cover and the ceramic mask can make the largest surface of the ceramic surface.The maximum electric field intensity at the three point junction of the inner side decreases with increasing the depth and width of the metal insert and increasing the ceramic angle.The critical breakdown field strength of SF6 is checked as the checking value,the structure of the upper part of the isolated switch room and the upper circuit breaker room is improved.The result shows that the insulation requirement is satisfied when the isolation switch room adopts the 25mm busbar structure with the round angle.When the circuit breaker chamber adopts 12mm thick busbar and the fillet surface of the bus bar is the junction surface of the fillet surface and the plane,it meets the insulation requirements.The influence of the structural size of the interrupter on the electric field intensity in the critical area is studied,the structure of the real arc extinguishing chamber is improved to reduce the electric field intensity in the key area.The results show that the elliptical mean pressure ring and 135 of the 5x2.5mm are selected.Angle ceramic structure;using the 2.5x2.5mm square insert and the elliptical angle of 3x4mm;it is more reasonable to use the shield of the 3mm to the arc chamber of the distance between the ceramic distance and the 46mm shieldThe empirical formula for calculating contact resistance and the formula of resistance calculation are used.The contact resistance model is set up according to the contact view,and the contact resistance model is set up with different resistivity and thin slice thickness.The simulation results show that the simulation results are slightly larger than the basic requirements of the switch cabinet temperature rise or insufficient temperature margin.By changing the circuit breaker's over travel and changing the bus bar thickness,make the contact resistance of the switchgear smaller,and the temperature rise meets the basic requirements of the temperature rise of the switchgear.The research of this topic is to improve the insulation performance of 40.5kV switchgear and vacuum interrupter,and provide a new solution for checking the temperature rise of switchgear.