Polypropylene (PP) film is widely employed as dielectric material in HVDC capacitors. The conduction loss leads to temperature rise and accelerates the breakdown of PP film, threating the safe operation of capacitors. In this paper, polycyclic compounds are employed to modulate the DC conductivity of PP film at different temperature. Three kinds of polycyclic compounds, 4-Benzoylbiphenyl, 4,4’-Bis (dimethyl amino) benzil and benzoin, were dispersed into PP matrix by banbury mixer with the filler content of 0.05 wt%. A stainless-steel mold was employed to make the composite materials into films. The three-electrode system was used to measure the conduction current of samples at different temperature. The DC conductivity and the conduction activation energy were calculated. Polycyclic compounds introduced deep traps and increased the deep trap density in PP film. The conduction activation energy and DC conductivity of PP film were decreased by polycyclic compounds, and the DC conductivity of PP film modified by 4-Benzoylbiphenyl is lowest. The introduction of deep traps by polycyclic compounds limits the transport of charge carriers. The conduction activation energy and DC conductivity of PP film are decreased by the addition of polycyclic compounds at different temperature.

Polypropylene film, DC conductivity, Temperature, Trap level distribution