Epoxy insulator is affected by surface charge accumulation under a strong electric field, which causes a decrease in the surface flashover voltage, threatening the safe operation of power equipment. This study reports on a flexible coating strategy for the insulator to inhibit the charge accumulation through numerical simulation. The experiment was conducted initially to reveal the charge accumulation feature. Then, the flexible coating method was proposed, in which the insulator surface was divided into three parts, and surface coatings with various conductivities were painted on the designated areas to adjust the charge distribution. Finally, the efficiency of such a coating strategy was estimated considering the temperature gradient. The results presented that the homo-charge was mostly deposited on the non-planar area of the spacer. The maximum charge density first decreased and then increased with increasing surface conductivity. The charge accumulation could be restrained by increasing the surface conductivity of insulator effectively. A significant suppression was achieved by properly coating with high conductivity at the nonplanar region and with low conductivity at the planar region. The suppression performance of such a strategy became reduced as the temperature gradient increased. The results indicate that the flexible coating can balance charge deposition in the non-planar region and restrain charge injection near the electrode, thereby inhibiting the charge accumulation.
In order to improve the thermal conductivity and the insulation properties of polyethylene (PE) used as cable insulation under DC stress, hexagonal boron nitride (h-BN) and inorganic particles have been considered as micro-filler and nano-filler, respectively. As a 2D material, the orientation of h-BN possibly affects the insulation properties of the polymer. It is important to understand the influence of the filler orientation on the insulation performance of the polymer. In this work, a numerical simulation has been performed to investigate the effect of orientation of micro-h-BN on charge transport and DC breakdown of PE-based micro/nano-composites and a comparison between the simulation result and previous literature data has been conducted. The h-BN was designated to be parallel, perpendicular to the normal sample surface vector (the direction of electric field in this work) or randomly distributed in the matrix, and the charge transport behavior and DC breakdown strength in the samples were discussed by using the bipolar charge transport (BCT) model. The results indicated that when the h-BN was perpendicular to the normal vector, the density of trapped charge was the largest and the DC breakdown strength was the highest among the three cases studied. It is suggested that the charge trapping/de-trapping processes and the electric field in the sample vary with the orientation of h-BN through tailoring the trap characteristics of the material.
Epoxy insulators are widely used in Gas-Insulated Transmission Lines (GILs), playing a significant role in electrical insulation and mechanical support. The metal particles generated during the production and operation of the equipment aggravate surface charge accumulation on the insulator, causing surface flashover. Therefore, it is necessary to study the suppression strategy of charge accumulation. In this paper, a downsized disc insulator was taken as the research object to investigate the effect of zoning coating on charge suppression with the presence of a linear aluminum metal particle under negative DC voltage. The zoning coating method was achieved by painting coatings with different conductivities in three areas on the insulator surface to regulate the charge. The inhibition mechanism of zoning coating on the charge accumulation in the presence of a linear metal particle was analyzed with the assistance of numerical simulation. The results showed that negative charges were accumulated in the nonplanar region as there was no metal particle, and the existence of metal particles led to the significant accumulation of positive charge speckles in the nonplanar region. The application of zoning coating could significantly inhibit the charge accumulation in the nonplanar area of the insulator and the charge injection from the grounded electrode to reduce the charge density. Under −25 kV, the maximum charge density on the insulator with the zoning coating was 48.1% lower than that without the coating, and the inhibition effect increased by 57.9% when the metal particle was introduced. This paper provides a new way to suppress the charge accumulation on the insulator surface.
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