The surface charge accumulation on the basin insulator is a particular problem in high‐voltage direct current (HVDC) gas insulated switchgears (GIS) and gas insulated transmission lines (GIL), which restricts the development and application of extra/ultra high‐voltage (EHV/UHV) technology. The surface charge distribution and anti‐flashover performance are closely related to the insulator shape. To obtain the optimal basin insulator, a shape optimisation model based on artificial bee colony algorithm was established, and the minimisation objective functions based on capacitive (initial) electric field distribution and resistive (steady‐state) electric field distribution were respectively constructed. The optimisation results of the two objective functions were calculated, and the electric field and charge distribution on the surface of the insulator before and after optimisation were evaluated and compared using the simulation model. The results indicated that the optimisation based on the capacitive electric field can significantly inhibit the surface charge accumulation, and the optimised insulator can significantly reduce the surface normal electric field and make the distribution of the tangential electric field more uniform, and the maximum tangential electric field can be reduced by 10%; the optimisation based on resistive electric field can achieve similar results, but requires more computational resources. Based on the results, the ‘anti‐charge’ basin insulator structure suitable for the DC field was given.

In order to suppress surface charge accumulation, a nano-SiC/epoxy composite with nonlinear conduction characteristic was employed to coat a pure epoxy substrate in this paper. Surface potential distributions on the insulator were measured after being charged by a pair of finger-shaped electrodes (one was powered at −10 kV, and the other was grounded). For the insulators with and without coating, there were mainly positive potentials on the whole surface, and the area with higher potential located near the high voltage electrode. As the charging time increased, the high potential area began to shrink, indicating a possible charge migration. When the charging time exceeded 60 min, the potential distribution was almost kept unchanged. Compared with the pure epoxy substrate, the amount of surface charges had a slight increment after being coated with 3 wt% nano-particles. The accumulated surface charges were progressively reduced when the content of fillers became higher. Especially for the samples with 7 wt% and 10 wt% ingredients, there was a sharp decrease of accumulated surface charges in the distributed area and magnitude from 40 to 60 min. In terms of surface trapping characteristics and nonlinear conduction of the composite, the effect of coating on the surface charge accumulation was discussed.

In order to clarify the mechanism of how surface coatings affect surface withstand ability of insulator at DC voltage, the study of surface flashover on SiC/Epoxy coated insulator was conducted and a method that how to determine the approaching flashover moment (AFM) was proposed. Based on the plate-insulator and finger shaped electrode arrangement, the flashover characters, as well as dynamic surface charge distribution during the applied voltage rising, were studied under two kinds of charging methods, i.e. compact and uncompact contact condition at electrode-insulator interface. It was found that the surface flashover voltage was increased with the increment of SiC contents in coatings. The dynamic surface charging evolution confirms that homo-charge accumulation was the main charging phenomenon approaching the flashover occurrence, and the evolution mechanism of dynamic surface charge distribution was also explained. In addition, the surface electric field at the AFM was calculated, then the effect of charge accumulation on flashover voltage was analyzed. At last, from the sight of charge accumulation, the influence of SiC contents on surface withstand ability at DC voltage was discussed.

Surface charge accumulation on silicon carbide (SiC)/epoxy coatings with different contents of SiC filler, 3, 5, 7, and 10 wt%, is investigated using flat samples of epoxy substrate. In the experiments, a pair of finger-shaped electrodes was attached to the sample’s surface using direct pressing and conductive adhesive providing two different types of contacts and, respectively, surface charging methods. The electrodes were energized by applying dc voltage for various time intervals and resulted surface charge distributions between the electrodes were measured. It was found that depending on the contact type, charging duration, and filler content, different patterns of homocharge or heterocharge appeared on the material surface. Physical reasons for the observed effects are analyzed based on the calculated electric field distributions in the experimental setup, results of the auxiliary tests on material charging in a limited air volume, and surface trap energy distributions measured by utilizing the isothermal surface potential decay (ISPD) method. Application of SiC/epoxy coating for controlling surface charge accumulation is discussed.

Surface flashover on an insulator caused by the charge accumulation at the gas-solid interface is one of the main reasons limiting the development of gas insulated equipment in high voltage direct current (HVDC) condition. Therefore, it is helpful to clarify the mechanism of surface flashover and surface charge behavior by measuring charge distribution with high accuracy. In this article, a surface charge inversion algorithm based on constrained least square filter (CLSF) is proposed for surface charge measurement in a shift-invariant system. By taking the image restoration technology as an analogy, the algorithm transfers matrix equation into frequency domain by 2-D Fourier transform, which significantly simplifies the computational process. Then the CLSF is used to suppress the noise signal and actualize the conduction from surface potential distribution to surface charge density distribution. The calculation process and accuracy of the algorithm are discussed in detail with the simulated examples, and the inversion performance of CLSF is compared with Wiener filter. At last, the effectiveness of the algorithm is verified by performing surface charge measurement and dust figure. This methodology gives an innovative idea of potential-charge transformation process with higher accuracy and stability, which benefits the development of surface charge measurement technology.