This paper deals with creeping discharges propagating over solid insulator samples in presence of a fluoronitrile mixture consisting of 10% of fluoronitrile and 90% of CO2, under positive and negative standard lightning impulse voltages, in point-plane geometry. The solid samples used are disks made of filled epoxy resin used for real GIS insulators. The experimental results are compared with those obtained with SF6 at pressure ranging 0.1 to 0.3 MPa, while the pressure of fluoronitrile mixture is chosen to match an equivalent dielectric strength of SF6. Different characteristic parameters are investigated namely the maximum length of creeping discharges versus the gas/mixture pressure and voltage polarity. In SF6, two regimes of discharges that depend on the voltage polarity are evidenced. Under positive impulse, the mixture presents similar properties as SF6. However, under negative polarity the maximum discharge length in SF6 is much longer than in the fluoronitrile mixture.

In able to fully integrate renewable energies and to stop to use fossil energy and nuclear power, there is a need to evolve the current electric grid in a new one called the supergrid. This new grid will be based on a mix of High Voltage AlternativeCurent (HVAC) and High voltage Direct Current (HVDC) junctions highly meshed with Gas Insulation Substation (GIS) as nodes. While HVAC GIS technologies are well mastered, HVDC ones are still at the beginning. One weakness of the equipment being dielectric insulators, industries may have to conceive new dielectric formulations or improved ones. This paper presents a list of properties and values to target for future dielectrics formulation. At the end, it highlights as well, the importance of health and environnement and how their consideration have to be at the same level of attention than the final properties of the dielectrics.