摘要:
A multilayer, heat shrinkable composite tube covering 120 is provided for a cable joint structure in which intimately joined layers define a semiconductive inner conductor shield 112, an insulation layer 114, and an outer insulation shield 116. Furthermore, a highly resistive semiconducting layer 111 is provided over the joint under the innermost layer 112 of the composite tube, forming a dual layer conductor shield for the joint. In the preferred embodiment, the entire composite tube is pressure extruded in a common operation and all three layers are simultaneously chemically cured and cooled, under pressure to provide the intimately joined layers of the composite tube. Subsequently, when the tube is shrunk over the joint the three layers shrink as a unit, so that there is no possibility of trapping impurities or gas bubbles between layers.
摘要:
Long lengths of a heat-shrinkable sleeve for use in splicing electrical cables are made in a continuous process. The sleeve 10 is formed round a permeable core into which fluid is introduced under pressure to expand the sleeve radially when heated. The core and sleeve are advanced together axially first through induction heater 40 then through heating pipe 56 followed by conical section 60 wherein the sleeve expands while hot lubricating fluid circulates through 56, 60. The sleeve and core then pass through cooling region 64 wherein circulating cooling medium is spaced from sleeve 10, followed by cooling region 66 where the medium contacts sleeve 10. After drying the material is wound on drum 90. Finally, the core is removed and the sleeve cut into lengths. The sleeve may include a stress graded compound made by heating a dimethyl silicone liquid to remove gas and mixing the liquid with a silicone carbide powder capable of passing through a 400 mesh screen, the volumetric proportion being 1 part liquid to 0.5 to 2.0 parts powder.
摘要:
Electrochemical tree-type decomposition of polyolefin electrical insulation 5 surrounding semiconducting shield 4 containing copper strands 2 with interstices 10 is retarded by causing a liquid, eg. triethylene glycol, having a resistivity >10 9 ohms/cm and dielectric constant
摘要:
The insulation shield in a power cable having thick polymeric insulation (12) is constructed of a metallic layer (14) radially spaced from but in electrical communication with an inner semiconducting layer (13) by an intervening helical wrap (15) of a semiconducting or high dielectric constant longitudinal structurally resiliently compressible substantially shape recoverable element. Various elements are described, both hollow and solid, with and without one flat longitudinal surface, and of both monolithic plastic and composite plastic and metal construction.
摘要:
Long lengths of a heat-shrinkable sleeve for use in splicing electrical cables are manufactured by providing an elongated impermeable core, extruding an elongated sleeve around and in contact with the core, and effecting an initial expansion of a portion of the sleeve to a larger diameter in an expansion zone (40) so that the sleeve separates and leaves a space between the sleeve and core. A fluid is introduced into the space under pressure via a fitting (62) at the downstream end of the sleeve. To begin the process, a permeable core (26) is used, and the sleeve is extruded around and in contact with the permeable core. A fluid is introduced under pressure from a fitting (52) upstream or downstream of the expansion zone through the permeable core to the inside the sleeve in the expansion zone, and the leading end of tt impermeable core is welded at (50) to the trailing end of th permeable core at a location upstream of the expansic zone. To form the sleeve, an inner compound and a thin lay of outer compound are applied in a crosshead (38a), and balance of the outer compound is applied around the sleev in a second crosshead (38b). Liquid nitrogen cools an stabilizes the inchoate sleeve at (110).
摘要:
Long lengths of a heat-shrinkable sleeve for use in splicing electrical cables are made in a continuous process. The sleeve 10 is formed round a permeable core into which fluid is introduced under pressure to expand the sleeve radially when heated. The core and sleeve are advanced together axially first through induction heater 40 then through heating pipe 56 followed by conical section 60 wherein the sleeve expands while hot lubricating fluid circulates through 56, 60. The sleeve and core then pass through cooling region 64 wherein circulating cooling medium is spaced from sleeve 10, followed by cooling region 66 where the medium contacts sleeve 10. After drying the material is wound on drum 90. Finally, the core is removed and the sleeve cut into lengths. The sleeve may include a stress graded compound made by heating a dimethyl silicone liquid to remove gas and mixing the liquid with a silicone carbide powder capable of passing through a 400 mesh screen, the volumetric proportion being 1 part liquid to 0.5 to 2.0 parts powder.
摘要:
O A high voltage solid dielectric cable wherein a coating (4) of high dielectric constant material is applied to the surface of the insulation layer (3) prior to the application of a seml-conducting insulation shield (5) which is formed of semi-conductlng tape wound helically over the coated insulation with overlapping adjacent edges. The combination of the high dielectric coating and the semi-conducting nature of the shield acts to reduce the occurrence of insulation deterioration caused by partial discharges in the gaseous voids formed under the tape in the regions of overlap (10). Scratches (7) in the insulation are filled with the coating thereby eliminating the occurrence of partial discharges within these scratches.