Partial discharge deterioration of epoxy resin for electronic parts

Effect of physico-chemical degradation of epoxy resin on partial discharge behavior

“…Moreover, at still longer testing periods we have observed that most of these low intensity (-1 to 10 pC) pulse type discharges, eventually disappear or are replaced by either minute pulse pseudoglow or pulseless glow discharges [7]. Others have confirmed our observations, in that the evanescence of the small pulse discharges represents in most cases a transition point to smaller discharges in the range of 6 1 pC [5,10]. Inordinately minute discharges have been observed to occur within dielectric bounded cavities by Bartnikas [ll, 1.21.…”

“…In fact, there is other evidence in addition to ours, based on microscopic analysis, which suggests that a significant portion of the degradation in occluded cavities may arise during the small pulse discharge regime [5]. Our experiments indicate that whereas during the first -200 h of PD activity, characterized by discharge pulses of charge transfer in the order of N 150 pC, liquids composed mainly of a mixture of nitric, formic, glycolic and glyoxalic acids, as well as other oxidized products such as aldehydes and alcohols are formed, and the appearance of oxalic acid crystals is associated with the transition time to the lower amplitude discharge onset.…”

Model for partial discharges associated with treeing breakdown: III. PD extinction and re-growth of tree

“…After longtime PD degradation in a void, an electrical tree with a fast growth rate which leads to the final breakdown was observed when the magnitude of the PD pulse decreased [6][7][8]. It was confirmed by methods of light emission [6] and Lissajous figure [8] that this reduction of PD in voids was due to the transition to the swarming pulsive mocrodischarges (SPMD), and the total PD charge did not decrease. However, similar experiments were rarely carried out to study the phenomenon in trees.…”

Surface and gas phase reactions arising with epoxy exposed to partial discharges

“…As found here, epoxy resin subjected to partial discharges in air exhibits initially large pulse or spark type discharges, typically hundreds of picocoulombs, which change with time to much smaller pulse discharges (few pC) that eventually transform to a glow type discharge as reported also earlier by the authors [1,2] and substantiated by others [7,9,12]. In addition it has been found that the pulse repetition rate decreases under similar conditions [ 131, so that essentially the overall pulse discharge intensity diminishes with time.…”