Modelling non-linear leakage currents on artificially polluted polymeric surfaces

The results of measurements and modelling of nonlinear low level leakage currents (LC) that appear on surfaces of nonceramic insulators are presented. Two possible causes for the non-linearity are discussed, i.e. (i) the formation of a dry band on a hydrophilic surface and (ii) water droplet deformation on a partially hydrophobic surface. These effects are separately evaluated in two sets of LC measurements on polluted polymeric surfaces during a hydrophobicity recovery process with continuous AC voltage and half wave AC pulses. In each case, model circuits (RC components) are adopted. Attempts are also made to estimate and optimise values for these RC components