Low loss self contained oil filled cables insulated with PPL for UK 400 kV transmission circuits

The 400 kV PPL (polypropylene/paper laminate) cable is a low loss cable, which has been developed in the UK in collaboration with the National Grid Company. The economic and current rating advantages to be gained from 400 kV PPL cable in comparison with the performance of the established design of paper insulated, low pressure OF (oil filled) cable. The advantages of the PPL insulation are that: it exhibits a low dielectric loss characteristic, which approaches that of the best extruded polymeric insulation, because of the excellent dielectric properties of polypropylene; and it has the ability of the OF cable to operate at relatively high insulation design stresses of 15 MV/m and greater. Such high design stresses are necessary to limit the diameter of the cable to a size that is practicable for purposes of manufacture, transport and installation