Transient Quenching Properties of Vapor Arc Formed in Silica Sand: Contribution of Vaporized SiO2 Mixture to DC Arc Extinction Performance

Abstract

The current-limiting fuse uses silica (SiO₂)-sand as arc quenching medium to increase a current-limiting performance during the DC arc quenching process. In order to increase the current-limiting performance of the fuse, a detailed understanding of an arc resistance $r_{\mathrm{arc}}$ rise process is necessary. This paper first carried out a 1000 A DC Cu arc quenching experiment using the silica-sand to obtain transient change in $r_{\mathrm{arc}}$, morphology of the arc, and arc temperature $T$ during the arc quenching process. As a result, a current decaying increased $r_{\mathrm{arc}}$. The arc was maintained in the cavity surrounded by the fulgurite during the current decaying process. The temperature of Cu/SiO₂ arc was 25–8 kK at a current region of 950–400 A during the arc quenching process. Second, we theoretically calculated an electrical resistivity $\rho$, and a thermal diffusivity $\alpha$ as vapor properties for the Cu/SiO₂ vapor mixture. As typical results, the admixing of the SiO₂ vapor into the Cu arc less increased $\rho$ of the Cu/SiO₂ vapor mixture at $T$ between 25 and 5 kK. The $\rho$ of the Cu/SiO₂ vapor mixture drastically increased due to only decay in $T$. In contrast, the admixing of the SiO₂ vapor into the Cu arc significantly increased $\alpha$ at $T$ between 15 and 8 kK. The present results indicate that an increase in $\alpha$ and consequent rise in thermal energy dissipation from the arc is the main role of the silica-sand vapor mixed with Cu arc in the DC fuse during the arc quenching process. The increased thermal energy dissipation due to the SiO₂ vapor admixing further decreases $T$ to rapidly rise $\rho$ and $r_{\mathrm{arc}}$ during the arc quenching process. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.