Melting process of different icing morphology under energized condition and its impact on ice flashover

Typical icing morphology, including bridged and non-bridged icicles, affects the electrical strength of energized transmission line insulators under melting conditions. During the experiment result shown in this paper, there are two kind of discharge patterns due to icing morphology difference. For non-bridged icicles, melting leading to droplet ejection was analyzed during flashover experiments. Electric field simulations showed that droplet ejection led to electric field distortion and partial discharge initiation. Two different discharge patterns were observed on non-bridged icicles, surface discharge and interior partial discharge. For bridged icicle morphology, partial discharge occurred from the air gap inside to cut off the icicle and elongated forward to penetrate through the whole icicle. This penetration required more energy, leading to increased flashover voltage compared to partially bridged icicles. Experiments and modeling show that droplet ejection is a critical initiation factor in ice flashovers, and non-bridged icicles are more vulnerable to this effect.