Study on the relationship between damage of oil‐impregnated insulation paper and evolution of phase‐resolved partial discharge patterns

Abstract

SUMMARYThis paper studied the relationships between evolution of phase-resolved partial discharge (PRPD) patterns and damaging characteristics, such as surface topography, surface roughness, and surface conductivity, and the constitution of gas within cavity for oil-impregnated insulation paper during the damaging process caused by partial discharge (PD). According to PRPD patterns, the damaging process can be divided into five stages. At each of the stages, surface conditions of insulation were analyzed by optical microscopy, scanning electron microscopy, atomic force microscopy, and high-resistance meter. Gas constitution was analyzed by gas chromatography-mass spectrometry, as well. Meanwhile, PRPD patterns of different gas constitution were compared, and analyzed, as well as those of different surface-damaging conditions. Results reveal that during the damaging process, the percentage content of electronegative gases descends and ascends alternately, and discharging types alternate between pseudo-glow (or glow) and spark. PRPD pattern of pseudo-glow-type discharge chiefly depends on the properties of weak electronegative gases generated during PD. PRPD patterns of spark-type discharge are chiefly determined by surface damage conditions. PRPD patterns of spark-type discharge manifest different levels of ''rabbit-ear'' and periodical features. The level of ''rabbit-ear'' feature is mostly determined by surface conductivity, while the level of periodical feature generally depends on surface trap density. In addition, surface roughness does not change shapes of PRPD patterns; however, the amount of discharge increases as the value of surface roughness declines.

A study of three methodologies for the detection of partial discharge in OIP

“…The PRPD patterns were similar in behaviour to the work reported in the literature where a triangular-like pattern was observed [9], which eventually resulted in insulation failure.…”

“…This merging was similar in characteristic to other PRPD measurements reported in the literature, which was caused by a spark-type discharge [9]. During stage 4, an increased PD maximum apparent charge and repetition rate was observed.…”

“…During stage 4, an increased PD maximum apparent charge and repetition rate was observed. This increased PD activity was likely to have occurred due to the increased deterioration of the insulation and further changes in the cavities gas composition and surface conditions [9]. The PRPD characteristics at this stage were found to have similar PRPD patterns to a belt-like shape that was reported for a comparable OIP air-filled cavity geometry [9].…”

“…2. The initial PD activity captured at stage 1 occurred on the ascending and descending regions of the applied voltage cycle, which was characteristic of an airfilled cavity defect at the initial stage of energisation [8][9][10]. Shortly after stage 1, the PD activity had a reduced maximum apparent charge and repetition rate.…”

“…Shortly after stage 1, the PD activity had a reduced maximum apparent charge and repetition rate. This reduction in PD activity was likely due to the changes in the gas composition and surface conditions within the cavity spaces [9].…”