Under DC voltage, the interface charge of the spacer in gas-insulated metal-enclosed transmission lines (GIL) and gas-insulated metal-enclosed switchgear (GIS) is prone to accumulate, and the charge is an important factor to induce surface flashover. On different spacers, the distribution of the electric field can be varied and affect the flashover greatly. This paper concentrates on the surface flashover induced by solid-gas interface charge accumulation in DC GIL/GIS. The electric field distribution of the real insulator and the electrode structure commonly used in research are analyzed and summarized into two distribution forms: the tangential-component dominant type and the hybrid type. According to the electric field distribution forms, how the density distribution and electric field distortion of interface charge influence the flashover voltage of spacer is reviewed, and the influence of metal particles on charge and surface flashover is reviewed as well. Efforts to understand the mechanism of the surface flashover have alse been tracked.

Trapped space charges in epoxy composite distort the electric field, which will induce the failure of the insulation system, and nano graphene oxide may inhibit the curing behavior of epoxy resin matrix. This paper analyzes how the two interfaces affect the electron traps of epoxy resin/graphene oxide systems with different nanofiller contents. The electron affinity energy of epoxy resin matrix and nano filler molecules in the epoxy resin/graphene oxide system is calculated based on quantum chemistry. It is found that nano graphene oxide has a strong electron affinity energy and is easier to capture electrons. Then the influence of the interface formed by the epoxy resin matrix and the nano graphene oxide on the electron transfer ability is calculated. The epoxy resin matrix contains the electron transfer ability of interfaces formed by nano graphene oxide and the molecular chain is different from that of unreacted molecules. The results can provide a reference for the modification of epoxy resin/graphene oxide nanocomposites.

Epoxy composites are extensively utilized in electrical equipment for insulation, including high-voltage power transmission systems, high-voltage electro-vacuum devices, and pulse power supplies. Under DC voltage, surface charge accumulation of epoxy insulators is identified as one of the main causes of insulation failure. In this study, an experimental platform for surface charge accumulation of epoxy composite insulators in vacuum is established, and the charge accumulation characteristics are measured based on the active electrostatic probe. The results show that the maximum surface potential amplitude under positive voltage can reach approximately 40 times that under negative voltage, showing the polarity effect. The spatial distribution of surface potential shows three distribution patterns: positive charge ripple, negative charge ring, and negative charge speckles. The space charge characteristics of epoxy composites are measured based on the pulsed electroacoustic method. It is found that the space charge injected into epoxy composites by the positive voltage can reach 2.55 times that of the negative voltage, which is an important cause of the polarity effect. Results provide the reference for design of vacuum insulation system.

Charge accumulation at the gas-solid interface of DC (direct current) spacers distorts electric fields, which severely hampers the development of DC gas-insulated equipment. The charge on the gas phase critically influences the distribution characteristics of the interfacial charge and electric field. This work investigates the influence of the average surface roughness Ra of conductors on the surface potential distribution of spacers, as well as the effects of temperature gradients and voltage polarity on charge accumulation. The results show that the surface potential on the spacers does not increase monotonically with Ra, but instead reaches a relative minimum at Ra=3.2 μm. The temperature gradient exacerbates the nonhomogeneous distribution of the surface potential on the spacers, resulting in the formation of regions with heteropolar potentials.The influence of protrusion morphology on conductor micro-discharge current was investigated. It was found that the electric shielding effect dominates at low aspect ratios, whereas an optimal morphology minimizing discharge current exists at high aspect ratios. This research provides references for designing conductor surfaces in DC gas-insulated equipment where gas-solid interface charging effects must be considered.