Covers the construction and dimensions for designs of single core cables having either aluminium or copper conductors, cross linked polyethylene (XLPE) or ethylene propylene rubber (EPR) extruded insulation, copper wire metallic screen and medium density polyethylene (MDPE) oversheath. These cables are primarily intended for use in substations. Test requirements and test methods are included which are intended to demonstrate the capability of the cables for operation at a sustained maximum conductor temperature of 90 deg C and for a maximum short circuit temperature of 250 deg C. Cables manufactured to this Specification have no special features to prevent the ingress and migration of moisture in the event of damage. Users are therefore recommended to consider this possible risk.