The design of reliable high voltage equipment remains a challenge nowadays. The surface charge accumulation at gas/solid interface is a major problem of HVDC GIS/GIL. The electric field can be distorted and the dielectric strength of the system can be thus reduced dramatically due to surface charges.

The development of HVDC networks leads to an increasing need of Gas Insulating Substations (HVDC-GIS). When an insulator is subjected to high thermoelectric dc DC stress, space charge accumulation can induce local increases of the electric field, which must be known and taken into account for the equipment design when the fields exceed several kV/mm.

This paper is aimed at the study of the propagation of discharge at the surface of solid insulator and the development of an analytical model of flashover in air.

This paper is aimed at the comparison of breakdown voltages of SF6 and mixtures at different concentrations of Fluoronitriles in CO2. The experiments are conducted in different electrodes geometries under DC and lightning impulse voltages.

This paper is aimed at the breakdown characteristics of Fluoronitriles – CO2 gas mixtures in different experimental conditions; these mixtures constitute promising substitutes to SF6 gas in high voltage applications especially gas insulating switchgear (GIS).