Behaviour and effect of conducting spiral particles under AC voltage in a gas insulated electrode system

The behavior and effect of various spiral particles made of conducting wires in an SF₆ insulated electrode system, exposed to AC voltages, are presented. The conducting spiral particle is an idealized form of the helical particles found in practice in the gas-insulated system. The results obtained for particles made of copper and aluminum wires show that the lift-off voltage of the particle is independent of the particle length, whereas the crossing and breakdown voltages are affected by the particle length. The longer the particle, the lower the crossing and the breakdown voltages. The lift-off, crossing, and breakdown voltages decrease when the particle diameter or pitch increases or when the diameter or the density of the wire from which the particle is made decreases, within the pressure ranges examined (1 to 5 bar). The lift-off and crossing voltages for particles with the same overall dimensions but with different pitches are not influenced appreciably by the gas pressure