Abstract: A polymer composition includes a crosslinked polyolefin with improved DC electrical properties. Prior to crosslinking, the polymer composition includes a polyolefin and peroxide, in which the peroxide is in an amount of less than 35 mmol —O—O— per kilogram of the polymer composition. A cable can be surrounded by at least one layer including the polymer composition.

Abstract: A cross-linked polymer composition includes a cross-linked polyolefin. Peroxide in an amount of less than 35 mmol —O—O—/kg polymer composition may be included in the polymer composition prior to crosslinking the polyolefin. Suitable polyolefins that can be cross-linked in the polymer composition include an unsaturated LDPE homopolymer and an unsaturated LDPE copolymer of ethylene with one or more comonomers. Such unsaturated LDPE polymer can contain vinyl groups, and the total amount of vinyl groups present in the unsaturated LDPE can be higher than 0.05/1000 carbon atoms. The cross-linked polymer composition can be used, for example, in producing a cross-linkable and cross-linked article such as a cross-linkable and cross-linked direct current (DC) or other type of power cable.

Abstract: 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 U0 is 450 kV or more. The type test includes subjecting the power cable to a DC voltage of 1.85*U0 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*U0, followed by additional 2 to 5 cycles during at least 4 to 10 days at positive polarity, and wherein U0 is 450 kV, or 525 kV, or more.

Abstract: A polymer composition includes a crosslinked polyolefin with improved DC electrical properties. Prior to crosslinking, the polymer composition includes a polyolefin and peroxide, in which the peroxide is in an amount of less than 35 mmol —O—O— per kilogram of the polymer composition. A cable can be surrounded by at least one layer including the polymer composition.

Abstract: A method for heat treatment of an electric power cable, the electric power cable including a polymer-based electrical insulation system with a polymer composition. The method steps include placing the electric power cable having the polymer-based electrical insulation system into a heating chamber and exposing the polymer-based electrical insulation system to a heat treatment procedure when the electric power cable is located in the heating chamber.

Abstract: 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 U0 is 450 kV or more. The type test includes subjecting the power cable to a DC voltage of 1.85*U0 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*U0, followed by additional 2 to 5 cycles during at least 4 to 10 days at positive polarity, and wherein U0 is 450 kV, or 525 kV, or more.

Abstract: A method for heat treatment of an electric power cable, the electric power cable including a polymer-based electrical insulation system with a polymer composition. The method steps include placing the electric power cable having the polymer-based electrical insulation system into a heating chamber and exposing the polymer-based electrical insulation system to a heat treatment procedure when the electric power cable is located in the heating chamber.

Abstract: An electric power sea cable including at least one cable core. The cable core includes an electric conductor, an electric insulation surrounding the conductor, and a protective sheath surrounding the electric insulation and acting as a water barrier. At least one outer layer surrounds the at least one cable core. The protective sheath is made of metal and the electrical power sea cable includes at least one friction reducing layer surrounding the at least one cable core and arranged inside of the at least one outer layer.

Abstract: An electric power cable including at least one electric conductor. An electric insulation surround the conductor and includes a polymer. A tubular protective sheath surrounds the electric insulation and acts as a water barrier that prevents water intrusion into the electric insulation. The protective sheath includes a metal as a main constituent. The cable includes at least one density-raising element of a material of higher density than the material of the protective sheath, in order to increase the density of the cable such that too large motions thereof are prevented when the latter is installed in open sea.

Abstract: A polymer composition with improved DC electrical properties and a cable surrounded by at least one layer comprising the polymer composition are provided.

Abstract: An electric power sea cable including at least one cable core. The cable core includes an electric conductor, an electric insulation surrounding the conductor, and a protective sheath surrounding the electric insulation and acting as a water barrier. At least one outer layer surrounds the at least one cable core. The protective sheath is made of metal and the electrical power sea cable includes at least one friction reducing layer surrounding the at least one cable core and arranged inside of the at least one outer layer.

Abstract: An electric power cable including at least one electric conductor. An electric insulation surround the conductor and includes a polymer. A tubular protective sheath surrounds the electric insulation and acts as a water barrier that prevents water intrusion into the electric insulation. The protective sheath includes a metal as a main constituent. The cable includes at least one density-raising element of a material of higher density than the material of the protective sheath, in order to increase the density of the cable such that too large motions thereof are prevented when the latter is installed in open sea.