In order to research the influence of moisture on oilpaper insulation system of power transformer,the samples of insulation paper and insulation oil are prepared in the laboratory to carry out the polarization current and depolarization current( PDC) tests,and the insulation condition of samples is analyzed in the time domain. The test results are conversed into complex permittivity constant by polarization conductivity,to analysis the insulation condition in the frequency domain. Taking the DC conductivity...