AC Flashover Characteristic at the Triple Junction of the Oil-Pressboard Insulation

IEEE Access

卷:8

Zhong Chen¹  Hao Wen²  Lin Cheng²  Yi Jiang²  Taiyun Zhu³  Jian Hao⁴ 

[1] Electric Power Research Institute of State Grid Anhui Electric Power Company Ltd., Hefei, China;

[2] NARI Group Corporation/State Grid Electric Power Research Institute, Nanjing, China;

[3] State Grid Anhui Electric Power Company Ltd., Hefei, China;

[4] State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing, China;

关键词: Oil-pressboard insulation;    triple junction;    ac surface flashover;    breakdown strength;   

DOI  :  10.1109/ACCESS.2020.3035847

来源: DOAJ

【 摘 要 】

Oil-pressboard insulation in transformers is prone to surface tracking or creeping discharge during operation. The oil-pressboard interface is believed to be one of the weakest points in the insulation system. In this paper, AC flashover characteristic at the triple junction of the oil-pressboard interface under a slightly inhomogeneous electric field has been studied. The results showed that the creeping discharge always started at the triple junction, then developed along the pressboard (PB) surface, and finally reached the opposite electrode. The reason was that the triple junction was subjected to the maximum electric field strength. The field strength corresponding to the breakdown of the pure oil gap (POG) was decreased with the increment in the gap distance between electrodes due to the volume effect. As a comparison, the field strength corresponding to the breakdown for PB only changed slightly with the gap distance. Besides, the breakdown electric field of both POG and PB hardly changed when the electrode diameter increased. The above results could be applied to the inverse calculation and estimation of the flashover voltage levels under longer gap distances with any electrode diameter. Moreover, the relative position of the oil gap and PB could influence the flashover voltage levels. The breakdown voltage with PB directly contacting the ground electrode was 10% higher than that with PB directly contacting the high voltage electrode. This could be explained by the different charge behavior. The obtained results could provide a reference for the insulation margin design in ultra-high-voltage transformers.

【 授权许可】

Unknown