Extra-high-voltage power cable
AssigneePirelli General plc
InventorsMalcolm A. Simmons, Julian G. Head
Life of this patent
Estimating the term…
Abstract
An extra-high-voltage power cable is provided with extruded insulation 3 over a conductor 1 thereof. The insulation comprises an inner layer 5 of an unfilled high density polyethylene or polypropylene material having a higher electric strength than the material of the insulation adjacent thereto in an outer layer 6 thereof.
Claims12
An extra-high-voltage electric power cable comprising:
- a conductor;
- a first at least semi-conductive screen around and contacting said conductor;
- an inner first insulating layer of an unfilled high density polyethylene or polypropylene material having a predetermined electric strength around said semi-conductive screen;
- at least a second insulating layer around said first insulating layer, sad second insulating layer having an electric strength less than said predetermined electric strength of said first insulating layer;
- and,
- a second at least semi-conductive screen around said second insulating layer.
A cable as claimed in claim 12 or 13 wherein each insulating layer is extruded and wherein the radial thickness of said first insulating layer is no greater than one-third of the combined radial thicknesses of the extruded insulating layers.
A method of manufacturing an extra-high voltage cable having a conductor, said method comprising:
- extruding a first layer of semi-conductive plastic material over said conductor;
- extruding an insulating second layer of unfilled high density polyethylene or polypropylene material having a predetermined electric strength over said first layer;
- extruding a third layer of an insulating material over said second layer, the last-mentioned said material having an electric strength less than said predetermined electric strength of said material of said second layer;
- and,
- extruding a further layer of semi-conductive plastic material over said third layer.
A method of manufacturing an extra-high-voltage cable having a conductor, said method comprising:
- extruding a first layer of a semi-conductive plastic material over said conductor;
- extruding an insulating second layer of unfilled high density polyethylene or polypropylene material having a predetermined electric strength over an din contact with said first layer;
- optically inspecting the interface between said first layer and said second layer through said second layer;
- and,
- after optically inspecting said interface, extruding a third layer of an insulating material over said second layer, the last-mentioned said material having an electric strength less than said predetermined electric strength of said material of said second layer.
Dependencies are inferred from the claim text.