57 / 2024-04-05 03:45:06

Definition of the minimal creepage distances of vacuum interrupters for application in SF6-free gas-insulated switchgear

Vacuum Interrupter,dielectric properties,gas-insulated switchgear (GIS),Alumina ceramics,SF6-Free,lightning impluse

Requirement for the compactness of vacuum interrupters (VI) in new SF6-free gas-insulated switchgear (GIS) makes definition of dielectric conception challenging. Choice of VI dimensions is defined by target performances (insulation levels prescribed by standards) and environment in which VI will be integrated (switchgear’s architecture). Limitation of VI size allows to increase interphase distance, distance between conductors and earthed structures of GIS and thus releasing dielectric stresses and giving more freedom for the choice of filling pressure of insulating gas. One of the main outline dimensions of VI is the height of the ceramic insulator. It’s a critical input parameter for the development of VI. The target of this paper is to analyse the impact of the ceramics height on the dielectric withstand of the VI at different gas pressures. Experiments were carried out on standalone (i.e. without additional dielectric stresses provided by the internal components of VI) ceramics samples with different heights in chamber with pressurized air. Estimation criterium was basic insulation level (BIL) withstand. The analysis allowed to set guidelines for the selection of ceramics height, depending on specified BIL value and filling air pressure. The results showed that with accurate mastering of electrical fields, rather compact ceramic insulators can be used for rated voltages up to 36kV.