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Concerning DC arc quenching phenomenon in silica sand filling space, we have proposed a new method for raising an arc column resistance (r col ) by use of polymer-material arrangement. This paper reveals physical factors for r col rise on the bases of experimental results using the following cylinders made of: (i) Quartz (SiO 2 ) and (ii) PMMA ((C 5 H 8 O 2 ) n ) with various inner diameters φ. For φ = 2 mm case, r col measured for a PMMA cylinder arrangement indicated higher r col at low current region, while almost same r col around current peak. For φ = 3 mm case, r col for the PMMA cylinder was lower than r col for the quartz case at high current region, while almost comparable between these conditions at low current region. For φ = 5 mm case, r col were almost same during the arc quenching process. To discuss the effect of the r col rise, the followings were also performed: (i) observation of cylinders after arc quenching and (ii) calculation of the electron density of SiO 2 /Cu or PMMA/SiO 2 mixture vapors. It is concluded that, at high current region, r col can increase due to the shrinking of the arc conductive diameter caused by the cylinder hole and the silica sand filled inside the cylinder hole. On the other hand, the admixing of the PMMA ablation vapor increases r col at low current region in the present experiment.

In this study, experiments pertaining to direct current (DC) interruptions are performed in an arc-quenching chamber filled with silica sand. First, the arc column resistance is measured during DC arc-quenching to demonstrate the elementary aspects of the arc in the silica-sand-filled space. Subsequently, an arrangement comprising a polymer cylinder between electrodes in the silica-sand-filled space is proposed to increase the arc column resistance during DC arc-quenching. A polymethyl methacrylate (PMMA) cylinder is used in the experiments. Measurement results indicate that the arrangement of the PMMA cylinder causes the arc column resistance to increase approximately twofold in comparison with the no-PMMA cylinder arrangement. Finally, the effect of increasing the arc column resistance is discussed in terms of PMMA and silica vapor.

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