大电流真空电弧中阳极熔化过程的实验与仿真研究

Experimental and Numerical Study on Anode Melting in High Current Vacuum Arcs

大电流真空开断过程中,阳极触头在电弧作用下的熔化过程极大地影响着开断结果。目前对阳极熔化的研究集中于铜及铜基合金,所涉及的材料热特性参数较为局限。为了在更大物性参数范围下剖析阳极熔化机理,该文对W、Mo、Cr、Fe四种材料开展了阳极熔化实验研究,同时建立电弧磁流体动力学模型及阳极传热模型对熔化过程进行仿真模拟。结果表明,在固定阴极为Cu的大电流燃弧实验中,四种阳极材料的临界熔化电流分别为14.0、11.9、8.6、7.5 kA;在阳极热过程模拟中,确定了阳极输入能流密度的空间与时间分布,并得到了阳极表面温度。四种材料的阳极最高温度均出现在燃弧时刻7.0 ms附近,临界电流下计算得到的阳极最高温度与相应材料熔点误差小于150 K。

Vacuum interrupters are widely used in the medium voltage level system with the excellent interruption capability,simple structure and low maintenance cost.Moreover,developing vacuum interruption to transmission voltage level is an ideal method to replace the greenhouse gas SF_(6) towards the dual-carbon target.Breaking capacity is the core technology of the circuit breaker,the development of vacuum breaking technology needs to be based on an in-depth understanding of its breaking mechanism.In high current vacuum interruption process,the anode melting process under vacuum arc greatly affects the vacuum interruption results.The process of melting and destruction of anodes under the high current vacuum arc has been a focus of research over the decades.However,the previous research on the anode melting mainly focused on copper and copper-based alloys,and the relevant material thermal parameters are relatively limited.In order to understand the anode melting mechanism in a wider range of physical parameters,this work conducted the experiments on the anode melting of The objective of this study is to obtain the influence of the anode material on the anode melting,therefore,to eliminate the interference of the arc evolution,the cathode material is set as Cu for the four investigate anode metals.In the experiments,the current is applied from low current to high current with an interval of 1.5 kA.A high speed camera is used to record the anode activity under different arc current.The experimental results show that the corresponding threshold melting current for W,Mo,Cr and Fe are 14.0 kA,11.9 kA,8.6 kA and 7.5 kA,respectively.The first melting of the four metals occurred at the arcing time of about 6.5~7.0 ms.Besides the experiments,this work numerically study the anode melting.A two temperature magnetohydrodynamic model is used to describe the vacuum arc with a developed cathode boundary.The arc plasma parameters could be obtained in the arc,such as the particle density,temperature,velocity and so on.An anode sheath is considered between the arc column and the anode.The spatial and temporal distribution of the heat flux density delivered to the anode is calculated.The anode input heat is dominated by electron energy,spatially distributed as an exponential function,and temporally varying with arc current.An enthalpy equation is used to describe the anode thermal process.Under the heat source of the input heat flux by arc column,the anode temperature is calculated during the arcing time.The results show that anode temperature first increases rapidly and then decreases slowly.The highest temperature of the four metals occurs around the arcing time of 7.0 ms.The anode thermal process is mainly influence by the heat conductivity,density and specific heat capacity of the anode metals.The simulation results effectively verify the experimental results,and the error between the maximum temperature value calculated under the critical current and the melting point of the corresponding material is less than 150 K.The results of this work clarify the influence of anode materials on the anode melting under a larger range of physical parameters,which is helpful for an in-depth understanding of the contact melting mechanism and provides a basis for contact material selection and development in vacuum switches.