特高压GIS隔离开关切合短母线过程中对地二次击穿机理仿真研究

Simulation Study on Mechanism of Secondary Breakdown to Encloser in the Process of Closing Short Bus-Bar in UHV GIS Disconnector Switch

近年来,在特高压气体绝缘开关设备(GIS)的操作过程中发现,隔离开关在切合短母线时会在断口间产生流注分叉对地二次击穿现象。传统有限元-通量修正(FEM-FCT)方法和粒子网格-蒙特卡罗(PIC-MCC)方法在仿真此类长距离气体流注放电分叉现象时,会因高昂的计算成本而难以应用。针对这一问题,该文提出了一种基于相场法的流注放电仿真方法,实现了双阳极流注放电过程中流注分叉现象的模拟,仿真结果与PIC-MCC方法对比证明了该方法的合理性。最后,采用该方法对特高压GIS隔离开关切合短母线过程中的流注分叉现象及其引起的二次击穿现象进了模拟,结果表明,屏蔽罩的屏蔽区域与二次击穿现象有直接关系,减小第一次击穿时的触头间距以及增大屏蔽罩的屏蔽区域,均可以有效地抑制隔离开关对地二次击穿现象。

Gas insulated switchgear(GIS)is the core equipment in ultra-high voltage(UHV)transmission engineering,and its reliability is directly related to the safe and stable operation of the power system.In recent years,the phenomenon of secondary breakdown to ground has been observed during the process of closing short busbar in the UHV GIS disconnector:In the disconnector,besides the discharge channel between the static and dynamic contacts,a discharge channel from the electrode to the ground is formed,which then lead to a fault warning.This problem poses a serious insulation threat to the UHV GIS equipment and affects the stable operation of the UHV GIS equipment.However,since previous studies were mainly concerned with the very fast transient overvoltage(VFTO)generated during the operation of the disconnector,and insufficient attention has been paid to the breakdown characteristics during the operation of the disconnector.Therefore,the current understanding of the mechanism of secondary breakdown during the process of closing short busbar in the UHV GIS disconnector is weak.To address this problem,the simulation work for the secondary breakdown phenomenon during the process of closing short busbar in the UHV GIS disconnector are carried out and analyzed.Firstly,a method for simulating the long distance stream discharge bifurcation with low computational cost is proposed,which solves the problem that the traditional stream discharge simulation methods require too much computational cost to simulate the long distance(hundreds millimeters or more)stream discharge bifurcation.Subsquently,the proposed method is compared with the particle in cell-Monte Carlo collision(PIC-MCC)method by taking a small size(several millimeters)model as an example,which proves the rationality of the proposed method.Compared with the calculation results of PIC-MCC method,the overlap area of the main streamer development path is about 90%,the overlap area of the secondary streamer development path is about 70%,the breakdown time difference is less than 11%,and the grid resources required for the proposed method are only 2% of the PIC-MCC method.Finally,the breakdown phenomenon during the process of closing short busbar in the UHV GIS disconnector was repeatedly simulated by using the long distance stream discharge bifurcation simulation method based on the phase field method.The mechanism of the secondary breakdown was revealed and the factors affecting the secondary breakdown were explored.The results of the study reveal that if there exists a certain secondary streamer head develops outside of the shielding area of the shielding cover,when the first breakdown between the static and dynamic contacts is finished during the process of closing short busbar in the UHV GIS disconnector,the secondary breakdown between the contacts and the shell will occur.Increasing the curvature radius of the contact surface and reducing the burr defects on the contact surface,which can reduce the spacing between the static and dynamic contacts at the time of the first breakdown,will effectively limit the development of the secondary streamer,and then prevent the head of secondary streamer exceeding the shielding area of the shielding cover,and finally inhibit the occurrence of the secondary breakdown phenomenon during the process of closing short busbar in the UHV GIS disconnector.Increasing the size of the shielding cover to enhance its shielding area can also effectively inhibit the occurrence of the secondary breakdown phenomenon during the process of closing short busbar in the UHV GIS disconnector.