Solid DC cable

A solid DC cable comprising a conductor and an insulating layer provided on an outer circumference of the conductor, wherein the insulating layer comprises:

• a main insulating layer comprising kraft paper;
• a low-resistance insulating layer comprising low-resistance kraft paper having a resistivity smaller than that of the kraft paper of the main insulating layer;
• and
• a metal sheath on an outer circumference of said insulating layer, said low-resistance kraft paper being located just below said metal sheath or just below an outer semiconductive layer,
• wherein the low-resistance insulating layer is layered above the conductor in a region where the pressure of an insulating oil becomes negative when a load is cut off, and the low-resistance kraft paper is cyanoethyl paper.

A solid DC cable comprising a conductor and an insulating layer provided on an outer circumference of a conductor, wherein the insulating layer comprises:

• a main insulating layer comprising a composite tape in which low-loss plastic film and kraft paper are bonded;
• and
• a low-resistance insulating layer comprising kraft paper having a resistivity lower than that of the main insulating layer,
• wherein the low-resistance insulating layer is layered above the conductor in a region where a pressure of an insulating oil becomes negative when a load is cut off, a resistively (ρ1) of the kraft paper of the low-resistance insulating layer and a resistivity (ρ0) of the normal kraft paper have a relationship of 0.1ρ0≦ρ1≦0.7ρ0, and the low-resistance kraft paper is cyanoethyl paper.

A solid DC cable having a conductor and an insulating component, the insulating component comprising:

• a main insulating layer comprising one of kraft paper a composite tape having low-loss plastic film bonded with kraft paper;
• and
• a low-resistance layer having a resistivity less than that of the main insulating layer the low-resistance layer comprising at least one of carbon paper, kraft paper, low-resistance kraft paper and a tape layer having carbon paper and a low-resistance kraft paper,
• wherein the low resistance layer is layered above the conductor in a region where a pressure of an insulating oil becomes negative when a load is cut off so that the low-resistance layer helps to:
• 1) avoid a sharp change of temperature of the conductor that would otherwise be applied to the insulating component and 2) reduce shrinkage of the insulating oil so that a void in the insulating oil is not apt to occur in the insulating component.