Societa Cavi Pirelli S.p.a.

Industrie Pirelli S.p.a.

Industrie Pirelli Societa Per Azioni

Bernardino Vecellio

Gianmario Lanfranconi

A joint between a pair of electrical cables of different types, such as an oil filled cable and a cable with extruded insulation. Both cable ends have tapered insulation and stepped layers outwardly of the insulation and the conductor of one cable is mechanically and electrically connected to the conductor of the other cable by a rod surrounded by a body of insulation. Portions of the insulation at opposite ends of the body and the tapered insulations are respectively covered by insulation applied thereto during installation of the joint. The tapered insulation of the oil filled cable is enclosed by a housing in fluid tight engagement with the body and the sheath of the oil filled cable and filled with the oil of the oil filled cable. The insulation surrounding a portion of the body and the tapered insulation of the cable with extruded insulation is adhesively bonded to such portion of the body.

Joint for interconnecting two electrical cables of different types

Method and apparatus for replacing flammable, insulating oil in an oil-filled electric cable by non-flammable, insulating oil in which the flammable oil is withdrawn at least from the cable oil duct under vacuum and with heating of the cable to its maximum operating temperature and thereafter, the flammable oil which was withdrawn is replaced by non-flammable oil. During operation of the cable, oil which flows out of the cable during heating of the cable is sent to a first reservoir, through a check valve and during subsequent cooling, such oil is replaced by non-flammable oil from a second reservoir containing non-flammable oil and connected to the cable duct by a check valve. Also, an oil-filled cable having its insulation impregnated with flammable, insulating oil or a mixture of such oil with non-flammable, insulating oil and having an oil duct filled with a non-flammable, insulating oil which is different from the flammable oil.

Method and apparatus for replacing flammable oil in an electrical cable

An electric power cable insulating fluid which is a substance corresponding to the following formula ##STR1## where R is chosen between the following two radicals: ##STR2## and an electric power cable with its insulation impregnated with such fluid.

Electric power cable impregnated with insulating fluid

A flameproof electrical insulating fluid and an electrical cable impregnated with such fluid, the insulating fluid being a mixture of a polymethylsiloxane having a viscosity greater than 5 centistokes at 25.degree. C. and an aromatic compound corresponding to the chemical formula: ##STR1## where R is an aliphatic radical and said aromatic compound is present in the mixture in an amount from 0.5% to 10% by weight of the total weight of the mixture. Preferably, the aromatic compound is isopropyldiphenyl.

Flameproof electric cable impregnated with insulating fluid

A direct current electric cable has its conductor insulation formed by winding a tape of a biaxially oriented polymer provided on at least one face with a film of water-repellent grease.

Electric cable with insulation of biaxially oriented, polymeric tape

A product by process for reducing micro-voids in cross-linked cable insulation without reducing the voltage breakdown strength thereof in which process the insulation, after cross-linking, is heated at a temperature in the range from about 120.degree. C. to about 150.degree. C. and under a pressure less than 10 mm. Hg for a period from about 8 hours to 48 hours. Also, a cable having such insulation which has micro-voids less than about 10.sup.2 per mm.sup.3 and a perforation gradient greater than the perforation gradient of a cable which has not been so treated.

Electric cables of reduced micro-voids in the extruded insulation

A process for reducing micro-voids in cross-linked cable insulation without reducing the voltage breakdown strength thereof in which process the insulation, after cross-linking, is heated at a temperature in the range from about 120.degree. C. to about 150.degree. C. and under a pressure less than 10 mm. Hg for a period from about 8 hours to 48 hours. Also, a cable having such insulation which has micro-voids less than about 10.sup.2 per mm.sup.3 and a perforation gradient greater than the perforation gradient of a cable which has not been so treated.

Process for reducing micro-voids in the extruded insulation of electric

An insulating fluid for impregnating the solid insulation of an oil-filled electric power cable, particularly for a cable to be submerged in water, which comprises at least one lower aliphatic derivative of napthalene, preferably, 1 methylnapthalene or 1, 2, 3, 4-tetrahydronapthalene, or mixtures thereof or a mixture of one or more lower aliphatic derivatives of naphthalene with a conventional impregnating fluid. In the latter case, the derivative is present in a significant amount and preferably, is present in an amount sufficient to provide a specific gravity substantially equal to the specific gravity of water. Also, an electric power cable having its insulation impregnated with such insulating fluid.

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Milan, Italy

Bernardino Vecellio