Detection and Identification of Conducting Paths in Capacitor Tissue

A mercury electrode tester is described, with an operating range of 10-500 V, for recording the incidence of conducting paths in capacitor tissue. Conducting inclusions detected with this instrument have been studied by scanning electron microscopy and electron probe microanalysis techniques. They have been shown to include both carbonaceous and metallic particles. It is concluded that the mercury electrode tester can detect gross conducting particles short circuiting the sheet at the lowest test voltage; thin spots and porous areas that break down at higher voltages; and smaller particles embedded in the sheet that give rise to low resistance areas by partial breakdown at higher voltages. The techniques described provide means for rapid, quantitative assessment of capacitor tissues and also for identification of the nature of the conducting particles found.