In order to distinguish the influence of aging state and moisture on frequency domain spectroscopy（FDS） and improve accuracy of assessing aging state and moisture content of oil-paper insulation

we put forward an evaluation method based on frequency domain dielectric spectroscopy and compensation factor. In the proposed method the frequency domain dielectric spectroscopy method was firstly used to test sets of oil-paper insulation samples which were prepared in the laboratory with different degree of aging and water content. Then

based on the measured spectrum curves

the feature quantities of aging degree and moisture content were proposed

and the aging factor and moistore compensate factor were first introduced to compensate the influences of them respectively. Finally

a new method was proposed to evaluate the condition of oil-paper based on compensation factor

and field tests were carried out to verify the validity.The experimental results show that the FDS at the low frequency range（10-3～10-1 Hz） is affected by both water and aging; at the high frequency range（101～103 Hz） the FDS is mainly affected by moisture when the moisture content is on a low level; however

when the moisture content reaches a high level

the effect of aging degree on this band will become obvious. Sm and SDP are extracted as characteristic parameters of moisture content and aging degree

respectively

and compensation factors can reflect and eliminate the effects of aging or moisture in the feature. By employing this method to evaluate the moisture content and polymerization degree of active transformers

the results are similar to the measured values

and the effectiveness of the method is preliminarily verified. Therefore

the proposed method which is based on the compensation factor algorithm can provide an effective way for the status assessment of actual transformer.