Cable sheathing for facilitating insulation breakdown localisation - uses fault localisation wires threaded through spaces between inner and outer insulating layers

摘要

The sheathing comprises at least one electrically insulating layer enclosing an extruded plastics envelope, one of which has ribs or corrugations to provide a number of spaces between them extending along the length of the cable. At least one fault location wire is threaded through one or more of these spaces, which may also contain a ferromagnetic band or wire to reduce the effect of outside electromagnetic fields. Pref. the cable core has an insulating extruded plastics envelope with evenly spaced longitudinal ribs around its outside to obtain several spaces between the envelope and the surrounding insulating layer, also obtained by extrusion. These spaces contain fault localisation and/or service wires and conductor bands. The fault localisation wire comprises a wire with a wrapped paper insulation layer detecting the ingress of water.