Critical current for phase shift of dry-band discharge on wet polluted insulators

Abstract

This paper presents experimental results on the influence of the electrolyte on the phase shift of dry-band discharges. Two types of electrolytes (NaCl and MgCl2) were introduced to compare the case of potassium chloride (KCl), and a model electrode system including glass-filter electrodes wetted with an aqueous solution of the electrolyte was employed to simulate a dry band. In both cases, the continuous and intermittent dry-band discharges were observed. The gas temperature of the continuous and intermittent discharges was 6000–6200 K and 1700–1800 K, respectively. The gas temperature was independent of the electrolyte. The spectral emission intensity originated from nitrogen molecules (N2) was also independent of the electrolyte. On the other hand, the spectral emission intensity originated from the electrolyte depended on the electrolyte and was strongly affected by the peak value of the current during the continuous dry-band discharge. The peak value of the continuous current was independent of the electrolyte. Hence, the relation between the current peak and the spectral emission intensity originating from the electrolyte during the continuous discharge was examined. As a result, the critical current was found to be approximately 3 mA irrespective of the electrolytes examined (KCl, NaCl and MgCl2).