Electric charge and field at lift-off for metallic particles in GIS

The charge on elongated metallic particles of various shapes in contact with a grounded plane and subjected to an electric field was calculated by finite element calculations. The result was compared with analytical expressions representing the charge on metallic particles often used when calculating the motion of metallic particles in gas-insulated systems. The comparison shows that more charge usually accumulates on particles with sharp edged ends. Furthermore, an algorithm is presented in which the electric field required to lift a metallic particle of arbitrary shape off a grounded electrode is calculated. The result show good agreement with previously derived analytical expressions of the lift-off field for well-defined metallic particles