Insulation Behavior of Small-air-gap for the Molded-insulation System (2)

—Partial Discharge Behavior of MGM and MGI Systems—

Abstract

Insulation discharge behavior of small-air-gap for the molded insulation system has been investigated in view of the Paschen curve. Two electrode systems Metal-Gap-Metal (MGM) and Metal-Gap-Insulator (MGI) were employed as the test samples. It was found that the V_s (breakdown voltage of the air gap) in the Paschen left region was determined in terms of glow-like discharge with slow micro-second order of discharge-current probably due to the ionic current for both MGM and MGI electrode systems. In the minimum and right regions of the Paschen curve for MGM, the partial discharge showed the streamer-like discharge current with relatively short rise-time and short discharge-duration. For the MGI-electrode system, however, the discharge type was found to lie in all glow-like discharge with small discharge current. The glow-like discharge, Townsend and streamer discharges were also recognized by the high speed CCD camera photographs.