A transmission cable includes a conductor or a bundle of conductors extending along a longitudinal axis, which is circumferentially covered by an insulation layer having an extruded insulation material, whereby the transmission cable passes the electrical type test as specified in Cigré TB496, whereby the rated voltage U.sub.0 is 450 kV or more. The type test includes subjecting the power cable to a DC voltage of 1.85*U.sub.0 during 10 to 15 cycles at negative polarity, followed by a polarity reversal with another 10 to 15 cycles at positive polarity at a DC voltage of 1.85*U.sub.0, followed by additional 2 to 5 cycles during at least 4 to 10 days at positive polarity, and wherein U.sub.0 is 450 kV, or 525 kV, or more.

Provided is a semi-conductive composition for a power cable, more particularly, a semi-conductive composition for a power cable having excellent mechanical properties and electrical properties, and more specifically, a semi-conductive composition for a power cable capable of having improved scorch stability, improved surface smoothness, improved space charge accumulation suppression characteristic to thereby be applicable to an ultra-high voltage direct current power cable.

Provided is a power cable, particularly, an ultra-high voltage underground or submarine cable for long-distance direct-current transmission. Specifically, the present invention relates to a power cable which includes an insulating layer of high dielectric strength, is capable of uniformly and effectively alleviating an electric field applied to the insulating layer, is particularly structurally stable, has high flexibility, and is capable of suppressing partial discharge, dielectric breakdown, etc. of the insulating layer, thereby increasing the lifespan and productivity of the cable.

Provided is a direct-current (DC) power cable. Specifically, the present invention relates to a DC power cable capable of preventing both a decrease in DC dielectric strength and a decrease in impulse breakdown strength due to space charge accumulation, and reducing manufacturing costs without lowering the extrudability of an insulating layer and the like.

A field grading composite body includes a polymeric matrix and a particulate filler distributed within the polymeric matrix. Particles of the particulate filler include a core formed from a semiconductor material, an oxide mixed layer deposited on the core, and conducting oxide layer. The conducting oxide layer deposited on the oxide mixed layer to provide an electrical percolation path through the polymeric matrix triggered by strength of an electric field extending through the field composite body. Conductors and methods of making field grading composite bodies for conductors are also described.

A cable for transmitting electricity may include a core including a first conductive material, a core shield surrounding the core, an insulation layer surrounding the core shield, the insulation layer comprising a material providing electrical insulating properties, an insulation shield surrounding the insulation layer; and at least one of the following at least partially surrounding the insulation shield: (a) a bedding layer including a first semi-conductive material, (b) a tape layer including a metallic tape intercalated with an insulating tape, and (c) a protection layer.

An alternating current (AC) power cable includes a conductor surrounded by at least an inner semiconductive layer including a first semiconductive composition, an insulation layer including a polymer composition, an outer semiconductive layer including a second semiconductive composition, and optionally a jacketing layer including a jacketing composition, in that order. The polymer composition of the insulation layer includes an unsaturated low density polyethylene (LDPE) copolymer of ethylene with one or more polyunsaturated comonomers and a crosslinking agent. The polymer composition of the insulation layer has a dielectric loss expressed as tan (50 Hz) of 12.010.sup.4 or less, when measured at 25 kV/mm and 130 C. according to Test for Tan measurements on 10 kV cables.

High voltage three-phase cable comprising three cores positioned so as to assume the configuration with minimum radial dimension and a sheath surrounding the three cores, wherein each core comprises an electric conductor having a substantially triangular shaped cross section with vertex portions and edges; an insulating system surrounding the electric conductor, the insulating system comprising an inner semiconducting layer surrounding the electric conductor, an insulating layer surrounding and in contact with the inner semiconducting layer and an outer semiconducting layer surrounding and in contact with the insulating layer, the layers of the insulating system being made of an extruded polymeric material having a dielectric constant comprised from 2 to 2.5; and a metallic screen surrounding the insulating system.

An energy cable comprises at least one cable core comprising an electric conductor, a crosslinked electrically insulating layer, and particles of a zeolite system comprising at least a first zeolite and a second zeolite placed in the cable core. A method for extracting crosslinking by-products from a cross-linked electrically insulating layer of an energy cable core comprises manufacturing the energy cable core comprising particles of the above-said zeolite system, heating the energy cable core up to a temperature causing migration of the crosslinking by-products from the crosslinked electrically insulating layer, and placing a metal screen around the energy cable core.

The invention relates to power cable polymer composition which comprises a thermoplastic polyethylene having a chlorine content which is less than X, wherein X is 10 ppm, a power cable, for example, a high voltage direct current (HV DC), a power cable polymer insulation, use of a polymer composition for producing a layer of a power cable, and a process for producing a power cable.