Overview of development, design, testing and application of compact gas-insulated DC systems up to ± 550 kV

Charge-induced surface flashover is a critical factor leading to insulation failures in high-voltage direct current (HVDC) gas-insulated equipment, and the underlying mechanisms are still unclear. In the present study, the impact of charge polarity and position on surface discharge characteristics in ambient air are studied, and the surface charge dynamics during multiple discharge process are also focused. The results indicate that the repulsive effect of deposited positive charges significantly inhibits the positive streamer development by reducing the electric field. The acceleration of negative charges on positive streamer propagation is the result of two competitive mechanisms: the enhancement of the electric field and the neutralization with positive charges in the streamer channel. In the multiple discharge process, positive streamers develop along the gap of positive streamer channels from the previous discharge. When the last discharge is intense enough, back discharges may occur along the pattern of the deposited positive channels from the previous discharge. These findings will be advantages in improving the insulation reliability of gas insulated equipment.

Section: Introductionmentioning

confidence: 99%

“…GIS for ±320 kV in 2023 and ±550 kV in the future [1,2]. Xidian Group Co., Ltd and Piaggio Group Co., Ltd in China are also engaged in the development of ±550 kV GIS [3,4].…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of charge-induced surface discharge under positive impulse voltages

Li,

Zhang,

Zhou

et al. 2024

“…In these scenarios, gas-insulated DC components offer an ideal solution compared to their air-insulated counterparts [1,2]. The compact and modular DC gas-insulated switchgear (GIS) drastically reduces space requirements by up to 95% for the DC switchyards and up to 10% for offshore wind platforms [3]. Following the first installation of an ±320 kV HVDC GIS within the DolWin6 (Germany) offshore converter platform in the North Sea recently, two further grid access systems, BorWin5 (Germany) and Sunrise Wind (USA), will be utilizing DC GIS to ensure reduced size and weight of the platform [4].…”

Section: Introductionmentioning

confidence: 99%

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

Zhang,

Li,

Min

et al. 2023

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.

“…The DC gas insulated switchgear (DC-GIS) is considered to be the optimal * Author to whom any correspondence should be addressed. choice for offshore converter stations due to its high reliability and small footprint [3,4]. However, the phenomenon of surface charging at the gas-solid interface is inevitable and can largely distort the electric field distribution, resulting in surface flashover failure, which is a critical issue impeding the development of DC-GIS [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Understanding the effect of SiC/epoxy coating on surface flashover under DC voltage: from surface charge accumulation

Han

Pan

Mao

et al. 2023

Charge accumulation at the insulator surface significantly alters the electric field distribution under DC voltage and can lead to unpredictable flashover. It is realized that the surface flashover voltage is reliant on the charge distribution approaching flashover occurrence (CDAFO). A method of how to judge the moment approaching flashover was proposed in this study to clarify how surface charges induced flashover, whereby the dynamic distributions of surface charges, including the CDAFO, were obtained from the instant of voltage application to the moment approaching flashover. The resulting flashover was analyzed with regards to insulators coated in SiC/epoxy, including an examination of the dominant charging pathway during voltage rising and a discussion of the relationship between the CDAFO and flashover voltage. Despite voltage polarities and SiC contents, the reversal of charge polarity from hetero-polar to homo-polar was observed during voltage rising. Furthermore, it was discovered that the CDAFO was homo-charge accumulation, and an increase in SiC content resulted in greater homo-charges. And a theory outlining homo-charge's enhancement of flashover voltage by weakening the electric field near the HV electrode was also proposed. Consequently, because of the improved effect of homo-charges on flashover voltage, the addition of SiC led to the boost of flashover voltage.