The relative parameters of initial discharge characteristics of partial discharge of oil-paper insulation under AC-DC combined voltage with different proportion are studied experimentally. Ball-plate electrode

column-plate electrode

and needle-plate electrode partial discharge models are constructed to simulate different defects. Theconstant voltage method is employed to conduct an experiment of partial discharge in oil paper under AC/DC com-bined voltage with different proportion

the variations of the relative parameters of partial discharge with the propor-tion of combined voltage are measured and analyzed. Results show that: 1)at the initial stages of partial discharge

the AC component amplitudes of the models of ball-plate electrode

column-plate electrode

and needle-plate elec-trode decrease

the DC component amplitudes increase

and the discharging numbers reduce with the rising voltageproportion;2)the ball-plate and needle-plate electrodes change their phase distribution to focus in the range of 90°to135°

extending to the direction of 45°;and 3)the maximum discharge of the ball-plate electrode is stable

the maxi-mum discharge of the needle-plate electrode decreases with the proportion

while the maximum discharge of the column-plate electrode increases with the proportion.