Studying corona onset characteristics after rime ice accumulation on energized stranded conductors

Rime makes conductor surface extremely rough and it will distort the electric field seriously. Numerous studies on icing conductors has been done but the fact that conductors operating under voltage are always ignored and Aluminum pipes are applied to study the actual conductors. Moreover, no clear information had been obtained into the decrease of regularities of corona onset voltage (COV) after energized icing. Therefore, a series of AC corona tests of charged rime icing had been done in the Multi-functional Climate Chamber. UV imaging technology and I-U curve fitting were applied to measure the COV and the finite element model was established to research field strength after icing. Results show that rime can bring COV down significantly. Ice-tree of rime in various shapes lead to different COV values. Increasing in icing time will raise COV values while the rising speed slowed down gradually. Conductivity has no impact on rime form or COV. The sharper ice-trees are, the more seriously electric field distorted and the lower COV values. This paper can provide information about design of transmission lines in regard to corona losses after icing.