Abstract. Interaction between thermal plasma and polymer solid powders was investigated using inductively coupled thermal plasma (ICTP) technique. Interaction between thermal plasmas and polymers is extremely important, for example, for design of down-sized circuit breakers, because it fundamentally affects the interruption capability of the circuit breakers. The ICTP technique was used in the present work because it presents the advantages of no contamination and good repeatability. The polytetrafluoroethylene (PTFE), polymethylmethacrylate (PMMA), polyethylene (PE), and polyoxymethylene (POM) were treated as polymer materials. Numerical modelling for injection of polymer solid powders into Ar thermal plasma was also made including thermal interactions between thermal plasmas and polymer powders. Results showed that PMMA-ablated vapour has a higher plasma-quenching efficiency than others; the polymer solid properties affect the plasma-quenching ability indirectly. Comparison of the calculated results to experimental results, showed good agreement from the viewpoints of the spatial distribution of ablated vapour concentration and the average solid particle velocity.

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Gas circuit breakers have been developed to be small and have low operating energy. To reduce their operating energy, a self-blast technique has been used. The self-blast gas circuit breaker obtains high pressure by utilizing arc energy in a fixed-volume chamber. Consequently, the temperature of the blasting gas rises. However, when the gas temperature rises, the interrupting efficiency of SF 6 gas decreases. Therefore, gas temperature is an important parameter that determines the interrupting performance. Gas temperature and pressure in a thermal puffer chamber of a self-blast circuit breaker using a model circuit breaker were measured by using a parameter of interrupting current and arcing time to estimate the blast gas temperature for a large current. Gas temperature in the thermal puffer chamber of the model circuit breaker was measured by a micro-gap discharge method in which the gas temperature was calculated by the breakdown voltage of a micro-gap by using critical electric field strength data. Two micro-gaps were installed in a thermal puffer chamber. The measured behavior of the hot gas was compared with flow analysis. The hot gas mixing processes with the parameter of interrupting current and arc duration time were estimated. The inlet gas temperature depends on the interrupting current, but the blowing gas did not depend on the arcing time at high currents. Results show that the temperature of the gas flowing out from the thermal puffer chamber reaches 2000 K for a' large interrupting current of 57 kA.

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