Study on Adhesion Reliability and Particle Inhibition of Epoxy Resin Coating in DC GIL after Thermal Ageing Experiment

Abstract

The movement of metal particles is effectively inhibited when a DC GIL’s (gas-insulated transmission line) electrode is coated. This article aims to study the problem of coating falling off during GIL operation and the change in the particle-inhibitory effect after coating ageing. A closed constant temperature heating platform and a particle motion observation platform in an SF6 atmosphere were built. The epoxy resin coating was aged for 1200 h in an SF6 atmosphere at 160 °C. Pull-off and particle-lifting experiments were carried out for the samples. The experimental results show that the adhesion of the coating changes from rapid decline to slow decline, decreasing by 35.5%. The lifting voltage of particle startup gradually decreased, and the inhibition effect on particle activity decreased from 45.89% to 35.7%. The coating mass loss rate and surface morphology were tested to explain adhesion decline. Then, the dielectric constant, electrical conductivity and adhesion work between the coating and the particles, which are the key factors affecting the lifting of the particles, were measured. Compared with the adhesion work, the dielectric constant of the coating has a greater impact on the starting voltage. The dielectric constant of the coating decreases by 24.07%, and the conductivity increases, which weakens its inhibition of particles. After ageing, due to the decrease in the dielectric constant and the increase in the conductivity of the coating, the inhibition of coating on particles is weakened. This paper reveals the changes in coating adhesion reliability and particle inhibition in DC GIL, providing guidance for using and improving the performance of coatings in practical engineering.

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“…The gradually aged process would cause the medium's characteristics to change. It has been verified that the dielectric constant of the coating would decrease due to aging, which is the main reason for the weakened inhibition of the coating on particles [30]. Therefore, the coating layer degradation monitoring during its service process can provide an important reference for the engineers to prevent the premature appearance of corrosion degradation.…”

“…Therefore, the coating layer degradation monitoring during its service process can provide an important reference for the engineers to prevent the premature appearance of corrosion degradation. Herein, the situation of coating deterioration was simulated: One was adopting the Nondispersive model, where the conductivity change with the service time was taken into account but the static permittivity was not; the other established the epoxy coating as the Debye model, where both the dielectric parameters and conductivity change with the service time according to the values provided by the reference [30]. Figure 7 shows the simulation results of the aging coating using various medium models, where the epoxy coating layer was set at 380 µm thickness (a) in Nondispersive mode and (b) in Debye model.…”