Abstract:
A method in the manufacturing of an insulated electric high voltage DC termination or joint includes the steps of providing an insulated electric high voltage DC cable including an inner conductor; a polymer based insulation system, the polymer based insulation system comprising an insulation layer and a semiconducting layer; and an outer grounding layer; removing the grounding layer and the semiconducting layer in at least one end portion of the high voltage DC cable, thereby exposing the insulation layer in the at least one end portion of the high voltage DC cable; covering the insulation layer of the polymer based insulation system in the at least one end portion of the high voltage DC cable by a cover impermeable to at least one substance present in the insulation layer of the polymer based insulation system in the at least one end portion of the high voltage DC cable in a non-homogenous distribution; subjecting the insulation layer of the polymer based insulation system in the at least one end portion of the high voltage DC cable for a heat treatment procedure, while being covered by the cover, thereby equalizing the concentration of the at least one substance in the insulation layer of the polymer based insulation system in the at least one end portion of the high voltage DC cable; and removing the cover. Instead of using a temporary cover, which is later removed, as the impermeable barrier, a field grading adapter or joint body mounted at the end of the DC cable during the manufacturing of the high voltage DC termination or joint may be used.
Abstract:
An apparatus for enclosing a medium and/or high voltage unit connectable to an electric power system. The unit includes one or a plurality of electrical components and generates heat as a by-product during operation. The apparatus includes a housing including a main chamber housing a seat for holding the unit. The main chamber is arranged to house the unit. The housing includes at least one gas exit opening at an upper part of the housing and at least one gas entry opening. The housing includes a sound-absorptive gas exit chamber provided with the at least one gas exit opening. The housing includes a sound-absorptive gas entry chamber provided with the at least one gas entry opening. A first free heat convection path is provided inside the housing between the at least one gas entry opening and the at least one gas exit opening, via the gas entry chamber, via the main chamber and via the gas exit chamber, in order to provide cooling. Each of the gas exit chamber and the gas entry chamber houses at least one sound-absorbing member for absorbing sound produced by the unit during operation. At least one of the gas exit chamber and the gas entry chamber has at least one heat conducting wall and at least one free space provided between the at least one sound-absorbing member and said wall such that the first free heat convection path is provided inside the housing between the at least one gas entry opening and the at least one gas exit opening via the at least one free space.