Study of Arc Quenching Properties of SF_6 by Induction Thermal Plasma

本研究主要致力于研制一种标准的试验装置，以研究SF6气体的灭弧性能以及电极和喷嘴材料蒸汽对其的影响。该装置的一个基本特点是使用感应等离子体作为主等离子体源，使我们能够在任何高压条件下，如断路器中，在任何气体中产生清洁的高温等离子体介质。在1997年计划的最后一年，特别注意了电子附着的重要作用，即电子数密度的减少和电子能量的减少。利用这种等离子体技术，还研究了氮气的性质，作为一种未来的地球环境下的淬火介质家族。1)高压SF6感应等离子体的产生尽管直到上一年，等离子体的压力还被限制在200Torr软真空条件下，但首次在稳定模式下产生了760Torr感应SF6高压等离子体，这给出了更可靠的条件，接近断路器中的情况。2)S、F和Ar原子光谱的等离子体温度光谱测量表明，感应等离子体处于10000 K左右的高温。但是，与氮气相比，SF_6气体由于其更高的导热系数和电子附着效应，表现出显著的猝灭等离子体半径的特性。3)利用等离子体技术，定量地研究了1-%的铜蒸汽污染的影响，这增加了感应等离子体的电子密度，从而增大了感应等离子体的半径，从而降低了电流的开断性能。

The research is mainly devoted to develop a standard test device to investigate the arc quenching properties of SF6 gas and the influence of electrode and nozzle material vapors on it. A fundamental feature of the device is that the induction plasma is used as a main plasma source, which enable us to generate a clean and high temperature plasma medium in any kinds of gases at high pressure conditions like in circuit breakers. In the final year of the program, 1997, special attention was paid on the important effects of electron attachment, that is, decrease of the electron unmber density as well as the decrease of electron energy. The N2 gas properties was also investigated as a future quenching medium family with the earth circumstance by this plasma technique. Main results obtained are as follows ;1) Generation of High Pressure SF6 Induction Plasma Although until the previous year, the pressure of the plasma is limited to 200 torr soft vacuum condition, A high-pressure 760 torr induction SF6 plasma was firstly generated in stable mode, which give the more reliable conditions close to those occurring in circuit breakers. N2 induction plasma was also recognized to be generated at such high pressure.2) Measurement of Plasma Temperature Spectroscopic measurement with atomic spectra from S,F,and Ar revealed that the induction plasmas are in high temperature of around 10,000 K.However, SF6 gas shows a remarkable properties of quenching of the plasma radius due to its high thermal conductivity and electron attachment effect compared to N2 gas.3) Effect of Cu Vapor Contamination By using the plasma technique, the effects of 1-% Cu vapor contamination were studied quantitatively and this increases the electron density and thus the radius of the induction plama, which will result in a reduction of the current interruption performance.