Aiming at micro-moisture content detection of oil-paper insulation in the large power transformers above 110 kV voltage level

two-channel measurement technique in both time domain and frequency domain was employed to conduct testing experiment on the transformers in different degrees of depreciation in the field. The influences of the factors like temperature

frequency and micro-moisture content on the dielectric response were analyzed

and a qualitative analysis method of micro-moisture content in oil-paper insulation of a large power transformer was proposed. Furthermore

a formula for quantitative calculation of the micro-moisture content was developed by constructing a dielectric constant database of oil-paper insulation with different micro-moisture contents and on the basis of the medium response curve from the X-Y model.