Surface charge and flashover characteristics of fluorinated PP under pulse voltage

Abstract

Polypropylene (PP), with low loss and high dielectric strength, is widely used as dielectric for the metallised film capacitor (MFC). The electric ageing and dielectric breakdown of the dielectrics under high-voltage stress is a major concern in the research on polymer materials. Surface discharge and flashover may happen on the PP film between the metallised segments in MFCs, which can influence the dielectric property and cause the breakdown of insulation. Fluorination is effective on modifying the surface characteristics of the polymers, meanwhile retaining the bulk properties. The effects of direct fluorination on the surface charge and flashover characteristics of PP films under pulse voltage are experimented in this study. The samples with different fluorination time were prepared. Surface charging was performed by corona discharge using repetitive pulse power, which was applied to measure the surface flashover voltage as well. The experimental results indicated that the surface charge and flashover voltage were strongly correlated with the charge polarity, pulse frequency and fluorination time. It was suggested that the fluorination of certain time could significantly improve the decay rate of the surface charge as well as the surface flashover voltage of PP samples.