Measurement of dynamic potential distribution during the propagation of a local arc along a polluted surface

A new method for measuring the dynamic potential distribution during the propagation of a local arc along a polluted surface is described. In order to study the role of electric stress during the pollution flashover processes, a flat polluted glass plate model was designed. The measuring electrodes made with a strip of aluminum foil were stuck on the bottom of the plate, opposite to the side on which the local arc propagated. The capacitance between the polluted surface and the measuring probe, which is in series with an additional capacitor, was used to construct a potential divider. By means of the dividers and a magnetic tape data recorder, the dynamic potential distribution, the position of local arc, and its propagation velocity were measured. The results show that the velocity of arc propagation along a polluted surface is 0.2 to 1 m/s and that the maximum average potential gradient in the pollution layer is ≈0.5 kV/cm