Investigation of plasma-enhanced-fluorination treatment on epoxy resins for high-voltage DC applications

Charge build-up under high voltage DC is a significant concern in the transmission system as its presence may distort the local electric field. By chemically treat polymeric insulation via plasma-enhanced-fluorination (PEF) treatment, the charge transport characteristics of the material can be modified. In doing so, excellent surface properties similar to those of fluoropolymers can be attained without compromising the bulk properties of the original polymeric insulation. The change in chemical components at the surface of polymeric insulation should lead to a corresponding change in dielectric properties at the surface and consequently may suppress the occurrences of charge build up. In this paper, the performance of plasma-treated epoxy resins was investigated in term of its dielectric performances, and valid comparison is made between PEF and direct-fluorination treatment from author's previous work. The tests include surface current measurement and surface flashover performances using a pair of finger electrodes. The effect of moisture absorption on the treated surface was also discussed and proved to be the limiting factor in the improvement of dielectric properties of fluorination treatment. This research proved that the introduction of the fluorinated surface layer on epoxy resins does play a major role in improving the surface dielectric properties for the use as insulation spacer in high voltage DC GIS systems.