Nano powder of aluminium nitride (AlN) is one of the materials necessary for developing solid insulating materials with high thermal conductivities. This paper describes the results of chemical equilibrium composition calculations and the results of experiments in synthesizing AlN nano powder using transferred type arc plasma. In order to increase the AlN content in synthesized powder, ammonia was recommended as a reacting/quenching gas, to be blown into aluminium gas in a temperature range between 2000 and 2400 K. The AlN content increased by more than 99% on passing the synthesized powder through ethanol.

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SUMMARY When a fault arc occurs in oil‐filled electric power equipment such as transformers in transmission and distribution systems, it generates a flammable gas and a dynamic pressure rise that may trigger an explosion. The purpose of this fundamental study is to investigate the effects of the arc under electrical insulation oil on pressure rises in a closed vessel containing air and oil. In particular, this paper is intended to investigate the relationship between the pressure rises and the generated bubble behavior by the arc. The pressure rises in both air and oil are measured under experimental conditions involving an arc current ranging from 2.3 kA to 8.9 kA, an arc duration of 10 ms or 100 ms. Experimental results show that the behavior of a bubble affects the pressure rises in the air and the oil as low‐frequency pressure oscillation comparatively.

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SUMMARYThis paper describes the phenomenon of internal pressure-rise due to arcs ignited between metal rod electrodes in air. First, the internal pressure-rises in a closed chamber due to arcs were measured at currents within the range of 1 to 12.5 kA. The rod electrodes were made of copper, iron, and aluminum, and were 20 mm in diameter. The measurements showed that the maximum pressure-rise distinctly differed with each electrode material at the same total arc energy, namely, the maximum pressure-rise was the highest in the case of the aluminum electrode and was the lowest in the case of the iron electrode. Next, to quantitatively verify this difference, the internal pressure-rise was estimated, taking into account the energy balance in the closed chamber on each electrode material. It was found that the estimated pressure-rise approximately agreed with the above experimental results by taking into consideration oxidation reactions of the electrodes, melting and vaporization of the electrodes, and radiation loss of the arcs under certain realistic assumptions.

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