Surface fluorinated epoxy resin for high voltage DC application

Abstract

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 direct fluorination, and plasma enhanced fluorination process, 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 research, epoxy resin samples with various surface fluorinating conditions were formulated and treated. The samples then were characterised by SEM and EDX analysis, Raman spectroscopy, and DC surface conductivity measurements. To further explain the effects of fluorination treatment, modelling of the electric field and current density distribution had been carried out. Surface potential decay tests from corona discharge, as well as PEA measurements, show that there is a significant change in decay characteristics with the introduction of surface fluorinated layer. The decay mechanisms responsible for the observed phenomena were thoroughly discussed. The effect of moisture absorption on the treated surface was studied and proved to be the limiting factor in the improvement of dielectric properties of fluorination treatment. Finally, surface DC flashover test using a pair of finger electrodes were performed. 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.

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