Insight into charge-induced flashover at the gas–solid interface in DC gas-insulated systems

Abstract

The proliferation of urbanization and the integration of new energy sources have stimulated the development of gas-insulated transmission lines and switchgear (GIL/GIS). In particular, the compact DC GIS in offshore converter platforms will significantly reduce footprints for DC switchyards, exhibit exceptional climatic resistance, and facilitate the cost-effective connection of remote offshore wind farms and submarine links. Nevertheless, insulators used in GIS/GIL always suffer from surface charge accumulation under DC stress, which could distort and enhance the local electric field and thus trigger a flashover at the gas-solid interface if it exceeds certain magnitude levels. This susceptibility becomes a major concern affecting the reliability of DC gas-insulated systems. Beyond these engineering-related challenges lie fundamental physics problems involving mechanisms of charge accumulation and charge-induced flashover which still require exploration. To this end, this paper presents an overview of recent advancements on this topic whilst highlighting relevant issues to be addressed. Specifically, the surface charge accumulation phenomena under DC fields are reviewed, and the charging mechanisms are summarized from macroscopic to microscopic perspectives. Further, the correlation between surface charge and surface flashover is discussed. Moreover, recent developments in tailoring methods for surface charging are also presented. Finally, perspectives are given on current research progress and future needs.

Impact of Pressure and Temperature on Charge Accumulation Characteristics of Insulators in Direct-Current Gas-Insulated Switchgear

“…Under DC voltage, due to the long-term application of the unipolar electric field, the charged particles in the SF 6 and the carriers in the insulating material are gradually transferred to the gas-solid interface along the field lines, leading to a significant interfacial charge accumulation phenomenon occurring on the surface of the insulator in the GIS, triggering the electric field distortion of the gas-solid interface, which is prone to inducing the flashover of the insulators along the surface [2,3]. Nowadays, it is widely accepted that the charge distribution at the gas-solid interface is decided by volume conductivity, gas Energies 2024, 17, 2739 2 of 11 conductivity, and surface conductivity [4][5][6].…”