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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SUMMARYThis paper describes experimental and analytic studies on pressure rise and propagation phenomena due to high current arcs in a container with opened pipes. The shape of the experimental container was chosen taking into account underground common ducts. First, arcs were ignited in the container with varying diameter D and length L of the opened pipes and at arc currents of 4 kA to 12.5 kA and an arc duration of 0.1 s. Based on measured waveforms, the maximum pressure rise P and the pressure oscillation frequency P were obtained. It was found that there is a tendency for P to increase with decreasing D and increasing L, and that D has a much greater impact on P . In addition, the tendencies of P with changing D and L can be approximately explained by Helmholtz resonance. Second, a CFD model for the container with opened pipe was developed based on the experimental results, and simulations were performed. The simulation results were found to correspond to the experimental pressure rise. C⃝ 2014 Wiley Periodicals, Inc. Electr Eng Jpn, 190(3): 30-36, 2015; Published online in Wiley Online Library (wileyonlinelibrary.com).

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