Transmission and other electrical equipment can be exposed to overvoltages. Overvoltages can be caused by a number of reasons such as lightning strikes, transient surges, sudden load fluctuation, etc. In the event of an overvoltage, the insulating equipment such as the insulators on a transmission line or bushings in a transformer can be exposed to high voltages which may lead to their failure.
Arcing horns are protective devices that are constructed in the form of projections in the conducting materials on both sides of an insulator. Arcing horns are fitted in pairs. Thus in transmission lines they are found on the conducting line and the transmission tower across the insulators. In transmission lines, in the event of a lightning strike on the tower, the tower potential rises to dangerous levels and can result in flashovers across the insulators causing their failure. Arcing horns prevent this by conducting the arc across the air gap across them.
Arcing horns function by bypassing the high voltage across the insulator using air as a conductive medium. The small gap between the horns ensures that the air between them breaks down resulting in a flashover and conducts the voltage surge rather than cause damage to the insulator.The horns are constructed in pair so that one horn is on the line side and the other is on the ground side.
Arcing Horns are also used along with air insulated switchgear equipment. Air insulated switchgear are vulnerable to damage due to arcing. Arcing horns serve to divert the arc towards themselves thus protecting the switching equipment. The arcing horns serve to move the arc away from the bushings or the insulators.
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Hewlett
