Aging of non-ceramic insulators due to corona from water drops

The fundamental principles of water drop corona as an aging mechanism for n on-ceramic insulators are presented. It is demonstrated that water drops in the sheath regions enhance the electric field and may cause corona which c an play an important role in long-term performance. Electric field enhancem ent caused by water drops in different locations on the shed and sheath are demonstrated by means of electric field calculations and small scale exper iments. The threshold magnitude of the surface electric field for corona fr om water drops is presented for two silicone rubber surfaces having differe nt hydrophobic properties. The effect of water drop corona activity on the properties of the surface material is shown using small scale aging experim ents.