Temperature Measurement of Polyethylene Exposed to Partial Discharge

Abstract

We measured the temperature of a polyethylene film exposed to partial discharge using an X-ray diffractometer based on the fact that thermal vibration of the polyethylene molecules attenuates the diffracted intensity exponentially. Polyethylene (PE) resin is known to be a crystalline polymer that can adopt a folded chain conformation. In bulk, PE is composed of amorphous and crystalline regions. With increased temperature, the molecular chains move and the PE transforms from the crystalline state that exists before heating. When a film temperature was at less than 60 degrees above room temperature, the diffracted intensity was at the same value as at room temperature.Parallel plate electrodes (two glass plates with an aperture in between) were attached to the goniometer of the X-ray diffractometer to generate partial discharge. Discharge by the electrodes only did not change the diffracted intensity. As such, the effect of X-ray dispersion by the electric field or discharge-generated gas was considered. A discharge was generated by applying a PE film to each glass plate electrode and the change in diffracted intensity was recorded. After the discharge had stopped, the PE film was heated to determine the temperature which gave the same diffracted intensity as that obtained by discharge. The discharge was found to increase the temperature of the PE film by 16 degrees above room temperature. This temperature rise is considered an average value resulting from penetration of the PE film by X-rays.