直流电弧对导线电极侵蚀特性的仿真及实验研究

Simulation and Experimental Study on Electrode Erosion Characteristics of Wire by DC Arc

导线的绝缘劣化和接头处电极接触不良等因素时常导致电弧的发生。直流电流因其无过零点的缘故,发生电弧时会对设备造成极大的侵蚀损害,甚至造成失火。针对电流为几十安的光伏及直流配电网等直流电应用场景,基于磁流体动力学(MHD)理论并且考虑电弧与电极之间的能量耦合,建立了导线电极的电弧-电极多物理场耦合仿真模型。模型中电弧热源考虑了焓传递项,电弧与阴极能量传递过程中考虑了热电发射电子流与阴极表面温度的关系和电场隧道效应,研究分析了电弧系统的温度场特性,探究了在不同电流、导线截面积和导线电极间距情况下,直流电弧对导线电极的侵蚀程度。研究结果表明:电弧的温度在靠近电极的区域高于弧柱中心的温度,阴极附近的温度略高于阳极附近的温度;然而,阳极的温度始终高于阴极温度;并且,电弧电流越大或者电极间距越大,电极表面的侵蚀熔融区越大;线径越大,电极表面的侵蚀熔融区越小。仿真与实验均表明10mm^(2)导线截面积的导线要求通过的电流在20 A以下才能有效防范电弧对导线电极的侵蚀;仿真结果表明并不是增大电极间距便可减轻侵蚀,间距为2 mm时导线电极未发生侵蚀;50的电流需要选择35 mm^(2)以上导线截面积的导线才能有效防范电弧对导线电极的侵蚀。

Factors such as insulation deterioration of wires and the loose connection between electrodes often lead to arcing.Because the DC current has no zero-crossing point,it may cause great erosion and damage to the equipment when arc occurs,and even cause fire.On the basis of the theory of magneto-hydrodynamics(MHD)and after considering the energy coupling between arc and two electrodes,this paper establishes a multi-physical field coupling simulation model of arc and electrodes of wires in the field of DC electric system such as photovoltaic station and DC distribution network with current about tens of A.The enthalpy transfer term is considered as the heat source of arc model,meanwhile,the relationship between thermoelectric emission electron flow and cathode surface temperature besides electric field tunneling effect are both considered during the process of energy transfer between arc and cathode.The temperature field characteristics of the arc system is analyzed,the erosion degree of the electrode by the DC arc is simulated and observed under the conditions of different currents,wire diameters,and electrode spacing.The results of the study show that the temperature of the arc near the electrode area is higher than that in the arc column center,in addition,the temperature near the cathode is slightly higher than that near the anode.However,the temperature around the anode is always higher than that around the cathode.Moreover,with the increase of the arc current or the contact spacing,the erosion melting zone on the contact surface increases too.However,the erosion melting zone on the electrode surface decreases when the wire diameter increases.The simulation and experiment data show that current less than 20 A may flow through the wire area of 10 mm^(2) to effectively avoid from the electrode corrosion by arc.Similarly,the erosion can not be reduced by increasing the electrode spacing,and no erosion occurs when the electrode spacing is 2 mm.A wire area of above 35 mm^(2) should be adopted for 50 A to flow through to effectively prevent the erosion of arcs.