Analysis of icicle growth process of composite insulator under energized condition and its impact factors

Composite insulators are more vulnerable to ice flashover because of the short spacing. This paper was concerned with icicle growth under energized condition. Firstly, icing experiments were carried out to record the icicle length which was classified into three different stages, and show the effect of environmental parameters. Afterward, three characteristic quantities were proposed to reflect the performance of icicle growth, including natural icicle growth rate v_NE, dripping frequency f, and critical discharge position function φ(L), where v_NE determined the steady icing time, f and φ(L) determined the steady icicle length. Finally, according to the experimental and theoretical analysis, the relationship between environmental parameters and characteristic quantities were built to illustrate the mechanism of icicle growth. It was found that the applied voltage increase induced the partial discharges ahead of time to change discharge position function φ(L). Temperature was in proportion to natural icicle growth rate v_NE. Higher rainfall intensity provided sufficient liquid water content to improve dripping frequency f. Applied water conductivity only affected the icing morphology and was irrelevant with the steady icicle length. Pollution improved the electrical thermal effect and suppressed natural icicle growth rate v_NE.