Abstract: A high voltage, gas filled, pipe type electrical cable and method of manufacture thereof. The cable comprises a plurality of insulated conductors, each conductor having a central gas passageway and being gas permeable. The conductor is wrapped with tapes impregnated with an insulating oil, and the wrapped tapes are encircled by gas permeable layers and skid wires. Three of such insulated conductors are encircled by a gas impermeable pipe, and the pipe and the conductor passageways are filled with an insulating gas under pressure above atmospheric pressure so that both the interior and exterior surfaces of the wrapped tapes are subjected to such gas. Preferably, the gas is a mixture of sulfur hexafluoride and nitrogen at a pressure of at least 200 psig. The tapes are impregnated with the oil and drained before they are wrapped around the conductor so as to provide gaps between the tapes which are substantially filled with the gas.

Abstract: Apparatus for extruding a first layer of a semi-conductive plastic material around the conductor of an electric power cable and for extruding a second layer of plastic insulating material around the first layer as the conductor is advanced in which the extruder for the insulating material includes an extrusion head which comprises a body with a passageway therethrough for the passage of the conductor through the body and having at least one channel therein extending from the exterior thereof to adjacent one end of the passageway for supplying the insulated material around the conductor. An extrusion tip or tubular guide is disposed in the passageway for guiding said conductor and extends across part of the channel for contacting material exiting from the channel. The guide comprises a ceramic tube with a polished inner surface forming the innermost surface of the guide.

Abstract: Insulation for an electric power cable, and a power cable including such insulation, the insulation having an improved dielectric strength and being irradiation cross-linked polymeric material having mixed therewith carbon black having a particle size in the range from about 200 to about 500 millimicrons, the carbon black content being about 10% to about 40% of the weight of the mixture of carbon black and the polymeric material. Also, the cable insulation may be layers of different density polyethylene, at least one of the layers being the described mixture of polyethylene and carbon black.

Abstract: A stop joint for a pair of electric cables having fluid under pressure therein in which the fluid impermeable pipe or shield around the cable, which is spaced at its end from the bared conductor end to expose the cable insulation, is connected to the connector for interconnecting the cable ends by a multi-part stop tube having an intermediate portion of insulating material and a pair of end portions bonded to respective ends of the intermediate portion, the end portions being made of an insulating material rendered conductive by the addition of conductive material or of insulating material having a conductive layer thereon for forming electrodes for electrical stress distribution purposes. The electrodes have substantially the same coefficient of expansion as the material of the intermediate tube portion to prevent separation of the end portions from the intermediate portion with temperature changes.

Abstract: In a pipe type electric cable installation in which portions of the cable cores extend into a joint casing where the conductors of the cores are conductively joined, the portions of the cores within the casing are enclosed by tubes which are longitudinally curved, preferably, S-shaped, to restrict axial movement of the cores with varying load conditions, one end of each tube being anchored, at least with respect to longitudinal movement, to the casing.

Abstract: Insulation for an electric power cable, and a power cable including such insulation, the insulation having an improved dielectric strength and being irradiation cross-linked polymeric material having mixed therewith carbon black having a particle size in the range from about 200 to about 500 millimicrons, the carbon black content being about 10% to about 40% of the weight of the mixture of carbon black and the polymeric material. Also, the cable insulation may be layers of different density polyethylene, at least one of the layers being the described mixture of polyethylene and carbon black.

Abstract: High-voltage power cables with extruded dielectric plastic insulation, installed underground, have their life shortened by the formation of electrochemical trees in the insulation. This invention provides a high-voltage power transmission cable constructed with sealant in interstices of a stranded conductor that are not filled by the semi-conducting material of a conductor shield of the cable. The construction prevents or greatly delays the formation of electrochemical trees in the insulation of the cable. The sealant prevents entrance of air into the cable at cable ends, and the passage of the humidity of the air through the conductor shield to an interface between the conductor shield and the inside surface of insulation that surrounds the conductor shield.

Abstract: Extruded dielectric power cables installed underground have their life shortened by the formation of electrochemical trees in the insulation. Tree formation can be prevented if the insulation is initially dry and the cable construction is such that moisture cannot gain access to the insulation under operating conditions encountered during installation and underground use. This invention eliminates initial moisture and has a construction that greatly retards ingress of moisture to the insulation during installation when the cable is in service and prevents longitudinal movement of water along the cable due to accidental damage to the cable or electrical failure.

Abstract: This electrostatic shielding tape is a metal strip of low resistance and low reactance folded longitudinally over the length of an insulated power cable having a semi-conducting insulation shield surrounding its insulation. The longitudinally folded metallic tape has its edges free to permit expansion of the insulation and insulation shield, located directly under it, without significant deformation of the insulation and the insulation shield. When the tape is of a metal requiring a thin corrosion-protective coating, the coating on the side adjacent to the insulation shield is preferably semi-conducting to accept charging current from the insulation shield. It is a feature that the metal of the electrostatic shield is in electrical communication with the insulation shield. .Iadd.