Direct current cable with resistivity graded insulation, and a method of transmitting direct current electrical energy

Claim 2

An electrical cable for the transmission of high voltage direct current electrical energy which minimizes disproportional direct current induced electrical stresses through the insulation due to temperature changes comprising an elongated metal electrical conductor enclosed within a resistivity graded, composite body of polymeric dielectric insulation, said composite dielectric insulation comprising the combination of an inner layer of polymeric insulation of relatively high resistivity and a contiguous outer layer of filled polymeric insulation of relatively low resistivity, the inner layer of the polymeric insulation comprising a polymeric material consisting essentially of cross-linked polyethylene and the outer layer of the filled polymeric insulation consisting essentially of cross-linked ethylene-containing polymer selected from the group consisting of polyethylene and copolymers of ethylene and propylene containing about 25 to about 150 parts by weight of at least one filler selected from the group consisting of clay and titanium dioxide per 100 parts by weight of the ethylene-containing polymer.

Claim 3

The electrical cable of claim 1, wherein the cross-linked polyethylene of the inner layer contains up to about 75 parts by weight of clay filler per 100 parts by weight of the polyethylene.

Claim 4

An electrical cable for the transmission of high voltage direct current electrical energy which minimizes disproportional direct current induced electrical stresses through the insulation due to temperature changes comprising an elongated metal electrical conductor enclosed within a resistivity graded, composite body of polymeric dielectric insulation, said composite dielectric insulation comprising the combination of an inner layer of polymeric insulation of relatively low resistivity, the inner layer of the polymeric insulation being composed of cross-linked polyethylene containing about 50 parts by weight of clay filler per 100 parts by weight of the polyethylene and the contiguous outer layer of the polymeric insulation being composed of cross-linked polyethylene containing about 50 parts by weight of clay filler and about 5 parts by weight of carbon black per 100 parts by weight of the polyethylene.

Claim 5

An electrical cable for the transmission of high voltage direct current electrical energy which minimizes disproportional direct current induced electrical stresses through the insulation due to temperature changes comprising an elongated metal electrical conductor enclosed within a resistivity graded, composite body of polymeric dielectric insulation, said composite dielectric insulation comprising the combination of an inner layer of polymeric insulation of relatively low resistivity, the inner layer of the polymeric insulation being composed of cross-linked polyethylene containing about 50 parts by weight of clay filler per 100 parts by weight of the polyethylene and the contiguous outer layer of the polymeric insulation being composed of cross-linked polyethylene containing about 50 parts by weight of clay filler and about 5 parts by weight of carbon black per 100 parts by weight of the polyethylene.

Claim 6

An electrical cable for the transmission of high voltage direct current electrical energy which minimizes disproportional direct current induced electrical stresses through the insulation due to temperature changes comprising an elongated metal conductor enclosed within a resistivity graded, composite body of polymeric dielectric insulation, said composite dielectric insulation comprising the combination of an inner layer of polymeric insulation of relatively high resistivity and a contiguous outer layer of polymeric insulation of relatively low resistivity, the inner layer of the polymeric insulation being composed of cross-linked polyethylene and said contiguous outer layer of polymeric insulation being composed of cross-linked ethylene-propylene copolymer containing about 96 parts by weight of clay filler per 100 parts by weight of the copolymer.

Claim 7

An electrical cable for the transmission of high voltage direct current electrical energy which minimizes disproportional direct current induced electrical stresses through the insulation due to temperature changes comprising an elongated metal conductor enclosed within a resistivity graded, composite body of polymeric dielectric insulation, said composite dielectric insulation comprising the combination of an inner layer of polymeric insulation of relatively high resistivity and a contiguous outer layer of polymeric insulation of relatively low resistivity, the inner layer of the polymeric insulation being composed of cross-linked polyethylene and said contiguous outer layer of polymeric insulation being composed of cross-linked ethylene-propylene copolymer containing about 96 parts by weight of clay filler per 100 parts by weight of the copolymer.

Claim 8

An improved method of transmitting high voltage direct current electrical energy with an insulated conductor which minimizes disproportional direct current induced electrical stresses through the insulation due to temperature changes, comprising providing an elongated metal electrical conductor enclosed within a resistivity graded, composite body of polymeric dielectric insulation composed of the combination of an inner layer of polymeric insulation of relatively high resistivity and a contiguous outer layer of filled polymeric insulation of relatively low resistivity, said inner layer of polymeric insulation comprising a polymeric material consisting essentially of cross-linked polyethylene and said outer layer of filled polymeric insulation consisting essentially of cross-linked ethylene-containing polymer selected from the group consisting of polyethylene and copolymers of ethylene and propylene containing about 25 to about 150 parts by weight of at least one filler selected from the group consisting of clay and titanium dioxide per 100 parts by weight of the polymer, and transmitting direct current electricity through said insulated conductor.

Claim 9

An improved method of transmitting high voltage direct current electrical energy with an insulated conductor which minimizes disproportional direct current induced electrical stresses through the insulation due to temperature changes, comprising providing an elongated metal electrical conductor enclosed within a resistivity graded, composite body of polymeric dielectric insulation composed of the combination of an inner layer of polymeric insulation of relatively high resistivity and a contiguous outer layer of filled polymeric insulation of relatively low resistivity, said inner layer of polymeric insulation comprising a polymeric material consisting essentially of cross-linked polyethylene and said outer layer of filled polymeric insulation consisting essentially of cross-linked ethylene-containing polymer selected from the group consisting of polyethylene and copolymers of ethylene and propylene containing about 25 to about 150 parts by weight of at least one filler selected from the group consisting of clay and titanium dioxide per 100 parts by weight of the polymer, and transmitting direct current electricity through said insulated conductor.

Claim 10

The method of claim 5, wherein the cross-linked polyethylene of the inner layer contains up to about 75 parts by weight of clay filler per 100 parts by weight of the polyethylene.

Claim 11

The method of claim 5, wherein the outer layer of filled polymeric insulation comprises clay filler in amount of about 50 to about 96 parts by weight per 100 parts by weight of the polymer.

Claim 12

The method of claim 5, wherein the outer layer of filled polymeric insulation comprises titanium dioxide filler in amount of about 115 parts by weight per 100 parts by weight of the polymer.

Claim 13

An improved method for transmitting high voltage direct current electrical energy with an insulated conductor which minimizes disproportional direct current induced electrical stresses through the insulation due to temperature changes, comprising providing an elongated metal electrical conductor enclosed within a resistivity graded, composite body of polymeric dielectric insulation comprising the combination of an inner layer of polymeric insulation of relatively high resistivity and a contiguous outer layer of polymeric insulation of relatively low resistivity, said inner layer of polymeric insulation being composed of cross-linked polyethylene containing about 50 parts by weight of clay filler per 100 parts by weight of the polyethylene and said contiguous outer layer of polymeric insulation being composed of cross-linked polyethylene containing about 50 parts by weight of clay filler and about 5 parts by weight of carbon black per 100 parts by weight of the polyethylene, and transmitting direct current electricity through said insulated conductor.

Claim 14

An improved method for transmitting high voltage direct current electrical energy with an insulated conductor which minimizes disproportional direct current induced electrical stresses through the insulation due to temperature changes, comprising providing an elongated metal electrical conductor enclosed within a resistivity graded, composite body of polymeric dielectric insulation comprising the combination of an inner layer of polymeric insulation of relatively high resistivity and a contiguous outer layer of polymeric insulation of relatively low resistivity, said inner layer of polymeric insulation being composed of cross-linked polyethylene containing about 50 parts by weight of clay filler per 100 parts by weight of the polyethylene and said contiguous outer layer of polymeric insulation being composed of cross-linked polyethylene containing about 50 parts by weight of clay filler and about 5 parts by weight of carbon black per 100 parts by weight of the polyethylene, and transmitting direct current electricity through said insulated conductor.

Claim 15

An improved method of transmitting high voltage direct current electrical energy with an insulated conductor which minimizes disproportional direct current induced electrical stresses through the insulation due to temperature changes, comprising providing an elongated electrical conductor enclosed within a resistivity graded, composite body of polymeric dielectric insulation comprising the combination of an inner layer of polymeric insulation of relatively high resistivity and a contiguous outer layer of polymeric insulation of relatively low resistivity, said inner layer of polymeric insulation being composed of cross-linked polyethylene and said contiguous outer layer of polymeric insulation being composed of cross-linked ethylene-propylene copolymer containing about 96 parts by weight of clay filler per 100 parts by weight of the copolymer, and transmitting direct current electricity through said insulated conductor.

Claim 16

An improved method of transmitting high voltage direct current electrical energy with an insulated conductor which minimizes disproportional direct current induced electrical stresses through the insulation due to temperature changes, comprising providing an elongated electrical conductor enclosed within a resistivity graded, composite body of polymeric dielectric insulation comprising the combination of an inner layer of polymeric insulation of relatively high resistivity and a contiguous outer layer of polymeric insulation of relatively low resistivity, said inner layer of polymeric insulation being composed of cross-linked polyethylene and said contiguous outer layer of polymeric insulation being composed of cross-linked ethylene-propylene copolymer containing about 96 parts by weight of clay filler per 100 parts by weight of the copolymer, and transmitting direct current electricity through said insulated conductor.

Claim 17

An improved method of transmitting high voltage direct current electrical energy with an insulated conductor which minimizes disproportional direct current induced electrical stresses through the insulation due to temperature changes, comprising providing an elongated electrical conductor enclosed within a resistivity graded, composite body of polymeric dielectric insulation comprising the combination of an inner layer of polymeric insulation of relatively high resistivity and a contiguous outer layer of filled polymeric insulation of relatively low resistivity, said inner layer of polymeric insulation being composed of cross-linked polyethylene and said outer layer of polymeric insulation being composed of cross-linked polyethylene containing about 115 parts by weight of titanium dioxide filler per 100 parts by weight of the polyethylene, and transmitting direct current electricity through said insulated conductor.

Claim 18

An improved method of transmitting high voltage direct current electrical energy with an insulated conductor which minimizes disproportional direct current induced electrical stresses through the insulation due to temperature changes, comprising providing an elongated electrical conductor enclosed within a resistivity graded, composite body of polymeric dielectric insulation comprising the combination of an inner layer of polymeric insulation of relatively high resistivity and a contiguous outer layer of filled polymeric insulation of relatively low resistivity, said inner layer of polymeric insulation being composed of cross-linked polyethylene and said outer layer of polymeric insulation being composed of cross-linked polyethylene containing about 115 parts by weight of titanium dioxide filler per 100 parts by weight of the polyethylene, and transmitting direct current electricity through said insulated conductor.

Claim 19

An improved method of transmitting high voltage direct current electrical energy with an insulated conductor which minimizes disproportional direct current induced electrical stresses through the insulation due to temperature changes, comprising providing an elongated metal electrical conductor enclosed within a resistivity graded, composite body of polymeric insulation composed of the combination of an inner layer of polymeric insulation of relatively high resistivity and a contiguous outer layer of polymeric insulation of relatively low resistivity said inner layer of polymeric insulation consisting essentially of cross-linked polyethylene and said contiguous outer layer of polymeric insulation consisting essentially of cross-linked ethylene-propylene rubber containing about 96 parts by weight of clay filler per 100 parts by weight of the ethylene-propylene rubber, and transmitting direct current electricity through said insulated conductor.

Claim 20

An improved method of transmitting high voltage direct current electrical energy with an insulated conductor which minimizes disproportional direct current induced electrical stresses through the insulation due to temperature changes, comprising providing an elongated metal electrical conductor enclosed within a resistivity graded, composite body of polymeric insulation composed of the combination of an inner layer of polymeric insulation of relatively high resistivity and a contiguous outer layer of polymeric insulation of relatively low resistivity said inner layer of polymeric insulation consisting essentially of cross-linked polyethylene and said contiguous outer layer of polymeric insulation consisting essentially of cross-linked ethylene-propylene rubber containing about 96 parts by weight of clay filler per 100 parts by weight of the ethylene-propylene rubber, and transmitting direct current electricity through said insulated conductor.