Creepage discharge on pressboards in synthetic and natural ester transformer liquids under ac stress

• Published in: IET electric power applications 2013-03, Vol.7 (3), p.191-198
• Main Authors: Yi, Xiao, Wang, Zhongdong
• Format: Article
• Language: English
• Subjects: ac stress; Applied sciences; bubble residences; commercial partial discharges detector; creepage discharge; discharge patterns; divergent electric field; Electric discharges; Electrical engineering. Electrical power engineering; ester viscosity; Esters; Exact sciences and technology; high‐ speed image recorder; Image detection; Liquids; Materials; mineral oil; Minerals; natural ester transformer liquids; oil‐insulated transformers; partial discharges; PB surface; pressboard surface; pressboards; Promotion; Recorders; synthetic ester transformer liquids; Testing. Reliability. Quality control; transformer oil; Transformers and inductors; viscosity; Wideband; wideband current measurement
• ISSN: 1751-8660; 1751-8679; 1751-8679
• DOI: 10.1049/iet-epa.2012.0303

This study reports experimental studies of creepage discharges on the pressboard (PB) surface in esters under ac divergent electric field. With the help of commercial partial discharges detector, wideband current measurement and high-speed image recorder, the differences of discharge patterns between open gap and on PB surface were studied in esters as well as in mineral oil. The results show that the presence of PB surface tends to promote discharges, especially negative discharges, and enables more discharges to occur at smaller phase angles. It is believed that the promotion effect of PB surface on discharges is caused by surface charges and bubble residences; because of more intense discharges and higher viscosity of esters, this effect is more significant in esters than in mineral oil.