Influence of fluorination time on surface flashover of polymeric insulation

2014 IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP)

Zhang

et al. 2014

Self Cite

Abstract-Epoxy resin has been extensively used for decades as an insulation material in high voltage transmission systems. However, this insulation material does suffer from bulk and surface charging when used as insulating spacer, mainly in high voltage DC applications. By applying fluorination treatment, the surface of polymeric insulation is chemically treated and so modifies charge transport characteristics of the material. In doing so, excellent surface properties can be obtained without compromising the bulk characteristics of the polymeric insulation. In this paper, the authors investigate the surface potential decay performance of non-fluorinated and fluorinated epoxy resin samples. The surface decay performance of insulating material is a crucial parameter in dissipating accumulation of surface and bulk charge that can lead to premature breakdown of the insulating material. The epoxy samples were characterised by Energy Dispersive X-Ray (EDX) analysis to determine the changes in chemical composition of the samples before and after fluorination treatment. Surface potential decay measurement using positive corona discharging was then performed, followed by bulk DC conductivity measurement to further explain the mechanisms which govern the surface potential decay. The existence of surface-fluorinated layer on the treated samples had been found to play a major role in dictating the movement of charges away from the surface during the decay process. The influence of fluorination treatment on the decay mechanisms was discussed.

Section: Resultssupporting

confidence: 82%

Section: Resultsmentioning

confidence: 88%

Mechanisms for surface potential decay on fluorinated epoxy in high voltage DC applications

2014 IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP)

Zhang

et al. 2014

Self Cite

“…4, in general, shows an increasing trend in DC surface breakdown strength with the introduction of fluorinated surface layer. Surface charge accumulation, which leads to surface flashover, is believed to be triggered by a field emission that occurs at the sharp edges of the electrodes under high-voltage DC stress [13]. The emitted electrons from protrusions on the rough finish electrodes drift in the direction of the electric field to reach the epoxy resin surface.…”

Section: Resultsmentioning

confidence: 99%

Influence of fluorination time on surface flashover of epoxy in insulating gas

2015 IEEE Electrical Insulation Conference (EIC)

2015

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Abstract-The accumulation of charges on polymeric insulation under high voltage DC stress is a major concern in the transmission system as its formation distorts the local electric field and has an adverse impact on the electrical performance. By undergoing fluorination treatment on the insulation, improved surface properties similar to fluoropolymers can be attained without changing the bulk properties of the original material. The change in chemical components at the surface of polymeric insulation should lead to a corresponding change in electrical properties at the surface and thus can suppress charge build up. Previous research on surface flashover on fluorinated epoxy resin at atmospheric condition shows a significant improvement in flashover strength. In this paper, the authors investigated the effect of different degree of fluorination treatment on cast epoxy resin on suppressing surface charge accumulation and its contribution towards the improvement in surface breakdown strength. In comparison to previous research, it has been found that there is an optimum time duration of fluorination treatment which improves the surface breakdown strength of epoxy spacer. The mechanisms that govern the effect of fluorination treatment on surface flashover were discussed.

“…Surface charge accumulation, which leads to surface flashover, is believed to be triggered by the field emission that occurs at the sharp edges of the electrodes under DC stress [140].…”

Section: Resultsmentioning

confidence: 99%

Surface fluorinated epoxy resin for high voltage DC application

IEEE Trans. Dielect. Electr. Insul.

Zhang

et al. 2015

Self Cite

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 directfluorination, 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