ABSTRACT
Insulation properties can be characterized as self-restoring and nonself-restoring. Self-restoring insulation has the ability to “heal” itself following a Âashover, and such insulation media is usually associated with a gas-air, SF6, etc. Examples include overhead line insulators, station buswork, external bushing surfaces, SF6 buswork, and even switchgear insulation. With self-restoring insulation, some Âashovers are o¶en acceptable while in operation. An EHV transmission line, for example, is allowed to experience occasional line insulator Âashovers during switching operations such as energizing or reclosing, or as a result of a lightning Âash striking the tower, shield wires, or phase conductors.
