Physics of microarcs in low-voltage switching devices

低压开关装置中微弧物理

• 批准号: 524731006
• 负责人: Dr. Margarita Baeva
• 金额: --
• 依托单位: Leibniz-Institut für Plasmaforschung und Technologie e.V. (INP)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/524731006?language=en
• 关键词: Physics; microarcs; low; voltage; switching

The project is aimed at the description and the physical understanding of low-current arcs (between 0.5 and 20 A) in low-voltage direct current (DC) switchgears. Low-voltage DC switching finds an increasing importance e.g. for electro mobility as well as in local grids that use photo-voltaic systems and batteries. Arc switching devices are attractive as low-cost solutions or in combination with semiconducting devices in hybrid switchgears because they permit a galvanic separation and a high insulation level. Although switchgears have been used for many decades, the basic understanding of the physical processes in switching arcs is still incomplete or even very poor in particular at low currents. An unexpected behaviour of the arc voltage and the arc radiation has been found for short gap lengths in investigations preliminary to this project, which cannot be described by conventional electric arc models. Moreover, low-voltage switchgear typically works with non-refractory electrode materials like copper alloys. The transfer of electric current from a non-refractory cathode to a low-current arc at atmospheric pressure is an open theoretical issue mainly because of the low thermionic electron emission even for temperatures close to the boiling temperature of non-refractory metals. These problems should be tackled in the project by combined experimental and theoretical studies. The focus is on arcs between flat cylindrical electrodes in ambient air at atmospheric pressure as a representative of most common low-voltage and low-cost switching devices. Copper composites as well as pure copper should be used as electrode materials. In particular, the voltage-current characteristics of the current breaking process for small and increasing gap distances, the spatial structure of the arc including electrode sheath regions and the arc attachment at the electrodes should be evaluated. A dominant role of metal vapour, distinct deviations from local thermodynamic equilibrium and the establishment of spot modes at both electrodes are expected and should be confirmed even for low currents. Therefore, a model switch will be set up, and the three-dimensional arc structure will be studied by high-speed imaging, tomography and spectroscopy. A multi-fluid non-equilibrium numerical simulation of the arc including the electrode sheath areas and the self-consistent coupling with models of the electrodes will be developed considering in particular the plasma chemistry in copper vapour. It is aimed in a self-consistent description of the current transfer and arc attachment at non-refractory cathodes for low currents, which is not available up to now. The model should explain the current-voltage characteristic and should be validated by the measurements at the model switch. Conclusions on the switching performance, the erosion of electrodes and the lifetime and long-term behaviour of the low-voltage switching devices should be drown.

该项目旨在描述和物理理解低压直流（DC）开关设备中的低电流电弧（0.5至20a）。低压直流开关越来越重要，例如，对于电动汽车以及使用光伏系统和电池的局部电网。电弧开关设备作为低成本解决方案或与混合开关设备中的半导体设备相结合具有吸引力，因为它们允许电流分离和高绝缘水平。虽然开关设备已经使用了几十年，但对开关电弧的物理过程的基本理解仍然不完整，甚至非常差，特别是在低电流下。在该项目的初步研究中，发现了短间隙长度的电弧电压和电弧辐射的意外行为，这是传统电弧模型无法描述的。此外，低压开关设备通常使用非耐火电极材料，如铜合金。在常压下，电流从非难熔阴极向低电流电弧的转移是一个悬而未决的理论问题，主要是因为即使在接近非难熔金属沸腾温度的温度下，热电子发射也很低。这些问题应在项目中采用实验与理论相结合的方法加以解决。重点是在大气压力下的环境空气中，作为最常见的低压和低成本开关设备的代表，扁平圆柱形电极之间的电弧。铜复合材料和纯铜均可作为电极材料。特别是，当间隙距离较小且不断增大时，电流断流过程的电压-电流特性、电弧的空间结构（包括电极护套区域）和电极处的电弧附着应进行评估。预计金属蒸气的主导作用，与局部热力学平衡的明显偏差，以及在两个电极上建立点模式，即使在低电流下也应该得到证实。因此，将建立模型开关，利用高速成像、层析成像和光谱学对三维电弧结构进行研究。电弧的多流体非平衡数值模拟包括电极鞘区和自洽耦合的电极模型将发展，特别是考虑等离子体化学在铜蒸气。它的目的是在一个自一致的描述电流转移和电弧附着在非耐火阴极的低电流，这是迄今为止不可用的。该模型应解释电流-电压特性，并应通过模型开关处的测量来验证。对低压开关器件的开关性能、电极的腐蚀、使用寿命和长期性能等方面的结论应予以重视。