Dry-Band Growth on Polluted Insulation

The power dissipated by leakage currents on the surface of wet polluted insulation leads to the loss of moisture from the pollution and the formation of dry bands. The growth of the dry band depends primarily on the surface temperature and on the temperature dependence of the surface resistance. Measurements of dry-band width for increasing applied voltage have shown that the lower the surface resistance, the lower the voltage necessary to initiate dry-band formation, and the more rapid its growth. The dry-band width is a function of the power dissipation in the band.