计及铜蒸气介质的小电流直流电弧仿真与实验

Numerical Simulation and Experiment of Small Current DC Arc Considering Copper Vapor Medium

因导线的绝缘劣化、接触不良等因素引起的直流电弧故障时有发生,但因无过零点特征无法自然熄弧可能导致设备损毁或者引发火灾,研究直流电弧特性对于电弧故障的检测与保护具有重要意义。光谱测试数据表明,在直流电弧中存在铜元素,因此,基于平衡态等离子体理论新增了含铜蒸气介质的电导率-温度特性曲线。建立小电流空气直流电弧的有限元模型,分析电弧稳定燃烧时的温度场分布和电弧电阻及电极间距的关系,同时,开展电弧实验,验证仿真模型的合理性。数据表明:相比纯空气介质,引入铜蒸气的仿真结果与实验数据更接近。这体现在当电弧稳定燃烧时,两者电极的温度场分布基本一致,等离子体气体温度最高到6000~7500K;电弧电阻和电极间距的仿真数据与实验数据最大偏差是2.283Ω,最大相对误差为13.45%。可见,含铜蒸气介质的电弧仿真模型能更准确、全面地研究直流电弧的电导率特性,为小电流直流电弧的电气特性和温度特性研究提供理论基础。

DC arc faults occur frequently due to factors such as insulation degradation and poor contact of cables.The DC arc can not be extinguished naturally because of no zero-crossing current/voltage so that it may cause device damage or fire.It is important to study DC arc properties for the detection of arc faults and safety protection for electrical appliances.Light spectral test data indicate the presence of copper particle in the arc.Therefore,conductivity-temperature characteristic curves of air containing copper vapor medium is proposed based on the equilibrium plasma theory.Meanwhile,a finite element model of small current air DC arc is built,then the temperature field distribution and the relationship between arc resistance and electrode spacing are obtained.By comparing experimental data and the simulation results,we find that the simulation data are much closer to experimental data when copper vapor is considered than that with pure air medium.When the arc burns stably,both the multiphysics field simulation and the experimental test show the similar temperature field distribution along two electrodes,in addition,the maximum gas temperature of plasma reaches 6000 K^7500K.The maximum deviation of arc resistance,versus electrode distance,between the simulation and experiment data is 2.283Ω,namely the relative error is 13.45%.Therefore,the arc simulation model considering copper vapor medium is more rational to study the conductivity properties of DC arc.Research work above provides a theoretical basis for electrical characteristics and temperature characteristics of small current DC arcs.