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Contribution of gas neutralization to the potential decay on silicon rubber surfaces at different ambient pressures

Surface charging and charge decay on insulating polymers are inherent phenomena in HVDC insulation systems and knowledge about them is essential for proper insulation design, testing and co-ordination. In the present study, surface potential decay on silicone rubber samples is analyzed at different pressures of ambient air. For both polarities of pre-deposited surface charges, the intensity of gas neutralization and its contribution to the total charge/potential decay are examined by means of experimental measurements. The results of the study indicate that gas neutralization is efficient at high magnitudes of surface potentials and for materials with relatively low conductivity. Reduction of air pressure weakens the intensity of the background ionization in gas and leads to diminishing amount of free ions. Under these conditions, the contribution of gas neutralization to the total charge decay is reduced and the decay process is determined solely by properties of solid material (bulk and surface electric conductivities).