Applicable to cast resin partitions pressurized with inert gases, for example, sulphur hexafluoride, carbon tetrafluoride, or a mixture of such gases, such as sulphur hexafluoride and nitrogen used in indoor and outdoor installations of high-voltage switchgear and controlgear, where the gas is used principally for its dielectric and/or arc-quenching properties, with rated voltages: (a) 1 kV and up to and including 52 kV and with gas-filled compartments with design pressure greater than 3 bar (gauge); and (b) 72.5 kV and above.