The New TV Front-end Protection Device Of Vacuum Arcing Chamber Design

Voltage transformer(TV)is the main measuring element in power system,the security of operation for the power network will affected by handing of the TV fault.The TV may be damaged even explode in practice,because the serious defects of the TV primary side of the 10 kV distribution network fuse quick-acting protection.The failure probability of TV in 10 kV switchgear and the front-end fuse is higher,the users of switch equipment directly open bypass breaker isolation from the TV,in order to save time when replacing TV and fuse,under the condition of the primary loop charged.There are security risks with this unconventional operations.And fuse replacement operation is complicated,time-consuming,influence safe and economic operation of power grid,it is urgent need to improve.A new type of TV front-end protection device to replace the existing fuse is designed,combining with the characteristics of vacuum switch technology.Existing vacuum arcing chamber have big volume and complex structure,causing the large dynamic contact quality and high brake force requirements,which is unfavorable for miniaturization design for the protection TV front-end device.In this paper,a new type of asymmetric bipolar longitudinal magnetic field contactor coil system is designed without change of dynamic contact shape,based on the existing empirical formula for 10 kV vacuum arcing chamber structure size.The contact have characteristics of simplifying the dynamic contact quality,reducing the brake force requirements,and improving brake speed.Electric field of vacuum arcing chamber is simulated with the finite element method.Two kinds of main structure corresponding improvement at the end of the shield vacuum arcing interior ministry of potential are analyzed and the whole domain electric field distribution is presented.The electric field distribution along the surface of main shielding enclosure,dynamic and static contact surface are compared.Resultsshow that the insulation performance of inside edge of shielded enclosure is better than the outside edge way,the electric field distribution is relatively uniform.The contact system model is created,the longitudinal magnetic field distribution is compared for the asymmetric structure and traditional structure.Then the influence of coil structure with its parameters and adding iron core are analyzed,the contact system conductor loop resistance,residual magnetic field and magnetic hysteresis time are simulated and calculated.The results show that the longitudinal magnetic field distribution produced by coil structure center area is small,the edge area is big.The eccentric longitudinal magnetic field distribution contribute to arc diffusion state,and improving the ability of large current breaking for arc chamber.The contact also have small conductor loop resistance,small residual magnetic field and magnetic hysteresis time is shorter,etc.Finally,the influence on the longitudinal magnetic field is analyzed for different ways of slots on contact blade in this paper.The results show that the slot way have less affected for the longitudinal magnetic field when current peak,but the residual magnetic field and hysteresis time have great influence when current zero-cross.The center cross slot way have the optimal performance.