Transformer faults induced by oil-paper insulation defect account for a big part in total transformer accidents.However

the existing diagnostic methods of transformer oil-paper insulation are unsatisfactory.Therefore

it is necessary to develop a non-destructive detection method for obtaining a characteristic quantity which can characterize oil-paper insulation aging state and be taken as an accurate and valuable reference in the assessment of transformer oil-paper insulation aging state.In this study

the frequency domain spectroscopy（FDS）based on frequency domain dielectric response was adopted.An accelerated thermal aging test for oil-paper samples was conducted in laboratory

and the influences of temperature on the FDS parameters under different conditions of oil-paper insulation were obtained.The results show that: the measured temperature significantly affects the oil-paper insulation aging state diagnosed by FDS;the frequency-temperature shift factor can convert FDS curve at any measured temperature to the one at same reference temperature to eliminate the influence of measured temperature on the FDS results.Preliminary results indicate that the FDS modified by frequency and temperature can beused to assess transformer oil-paper insulation aging under different temperatures.