A power cable includes a conductor; an inner semi-conductive layer covering the conductor; an insulating layer covering the inner semi-conductive layer, the insulating layer being impregnated with an insulating oil; an outer semi-conductive layer covering the insulating layer; a metal sheath layer covering the outer semi-conductive layer; and a cable protection layer covering the metal sheath layer. The insulating layer is formed by cross-winding insulating paper and impregnating the insulating paper with the insulating oil. The inner semi-conductive layer and the outer semi-conductive layer are formed by cross-winding semi-conductive paper and impregnating the semi-conductive paper with the insulating oil. A thickness of the outer semi-conductive layer is 7.5 to 15% of a total thickness of the inner semi-conductive layer, the insulating layer, and the outer semi-conductive layer.

Provided is a power cable, particularly, an ultra-high voltage underground or submarine cable for long-distance direct-current transmission. More specifically, the present invention relates to a power cable, in which an insulating layer has high dielectric strength, an electric field applied to the insulating layer is effectively reduced, and particularly, a large void is suppressed from occurring in the insulating layer when the power cable is left at low temperatures for a long time until electric current is supplied thereto after installed in a low-temperature environment, thereby effectively preventing partial discharge, dielectric breakdown, etc. from occurring due to an electric field concentrated in the large void.

A power cable includes an insulation layer, itself, having high dielectric strength. An electric field to be applied to the insulation layer is effectively buffered, degradation of the insulation layer can be prevented during a cable connection step such that the life of the power cable is extended and simultaneously, the thickness of the insulation layer is minimized such that an outer diameter of the cable is reduced, thereby enabling flexibility, ease of installation, workability and the like of the cable to be improved.

The present invention relates to a power cable and, particularly, to an extra-high voltage underground or submarine cable. Particularly, the present invention relates to a power cable in which an insulation layer, itself, has high dielectric strength, an electric field to be applied to the insulation layer is effectively buffered, degradation of the insulation layer can be prevented during a cable connection step such that the life of the power cable is extended and simultaneously, the thickness of the insulation layer is minimized such that an outer diameter of the cable is reduced, thereby enabling flexibility, ease of installation, workability and the like of the cable to be improved.

It is provided a power converter for transferring power between a high voltage DC connection and a high voltage AC connection. The power converter includes a power converter assembly including: a first converter arm, a first reactor, a second reactor and a second converter arm, connected serially between the positive and negative terminals of the DC connection. The high voltage AC connection is provided between the first reactor and the second reactor. Each one of the converter arms includes a plurality of converter cells and each one of the converter cells includes a switching element and an energy storage element. Both the first reactor and the second reactor are oil filled reactors.