Discharge Breakdown Characteristics With Fluorinated Polyimide Films in High-Temperature Superconducting Cable Insulation
The application of high-temperature superconducting cable now has been in the process of being implemented in power system. Polyimide (PI) film has been used as insulation in the high-temperature superconducting cable systems with the advantage of good performance in low temperature, excellent mechanical properties, and dielectric properties. However, due to the organic properties of PI films, it can be aged even brake down in the service of HTS cable. It is found that partial discharge in HTS cable can lead to insulation material degradation and finally breakdown. Our recent researches have shown that fluorination can influence the surface charge behaviors thus influence the PD characteristics of modified PI films. In this paper, PI films were fluorinated in laboratory, the relationship between the fluorination time and discharge characteristics of the films were researched. The surface topography of direct-fluorinated samples were obverted by using an Atomic force acoustic microscope. It can be found from the experiment results that the discharge times and quantity both showed decreasing tendency with the fluorination time increasing. The discharge breakdown voltage shows increasing tendency with the fluorination time from zero minutes to forty-five minutes, and then shows decreasing tendency.