Extension and upgrading of 420 kV GIS with SF6-free C4FN GIS solution

(GIS) on their assets based on SF6 technology. Recently many TO are switching to SF6-free solutions to reduce greenhouse gas emissions. SP Energy Networks are moving towards Net

Zero and are only installing SF6 when SF6 free solution are not viable. The move has been accelerated during the past 3 years thanks to the regulations, incentives and company policies in place in various parts of the world.

Manufacturers have initiated this move more than ten years ago with the first SF6-free solutions at 145 kV and 420 kV levels, using the C4FN technology (also named C4F7N or fluoronitrile technology). At 420 kV level, the first solution in place were limited to gas-insulated lines

(GIL). Recently the technology has been validated at 420 kV for full GIS, including switching devices like circuit-breakers.

Thanks to the excellent switching and dielectric properties of this C4FN technology, compactness of GIS solution can be maintained, and SF6-free GIS have very similar footprint than existing SF6 GIS solution. With this advantage, it has been possible to propose an extension and an upgrading of an existing GIS substation, at Kilmarnock South Substation, owned by SP Energy Networks.

1 The paper is describing how the existing GIS was extended with new SF6-free equipment

(except the circuit-breaker) and how the existing busbar elements were replaced by SF6-free busbar elements to cope with increased rating of the busbar from 4000 A to 5000 A. The GIS extension bays have been fully assembled in factory and delivered to site. The upgrading parts of GIS have also been assembled in factory and delivered to site. The work on site with replacement of existing SF6 parts by SF6-free new equipment is now finalized and the substation is energised.