The aging on HVAC and HVAC alternate with impulse on
contamination porcelain surface have been carried out.
Degradation on porcelain surface insulator with negative
polarity impulse excitation is higher than high voltage AC
excitation voltage. The further extension of dry band area due
to partial discharge accelerates the aging when specimen is
excited by HVAC or impulse excitation voltage.indicated the details when investigate not only on amplitude
of LC, but very significant necessary to investigate with
harmonics component content in LC signal.