high temperature superconducting (HTS)
In order to keep transmission losses as low as possible in power transmission, cables with superconductors and lowest impedances could be used in power transmission: Very Low Impedance Cables (VLI).
Corresponding VLI cables use high-temperature superconductors ( HTS). They have extremely low or no losses and can transmit many times more energy than conventional copper cables. There is no heat loss and the heat effects from the environment are compensated for by the cable design.
The development of HTS cables dates back to the 1960s. In order to create the effect of increased conductivity, the cables at that time were still cooled with helium at absolute zero of -273.15 °C, or 0 Kelvin. They were extremely complex in design and also very expensive. In the 1980s, ceramic materials and liquid nitrogen were used, which was cooled to -196 °C.
In terms of construction, there are two different HTS cables. In one, cooling by means of nitrogen takes place both inside the HTS conductor, which is wound around a tube as a conductor band, and through a tube surrounding the HTS conductor. In the other embodiment, the cooling device surrounds the entire HTS cable and its copper shield. In this context, the cable is referred to as a cold dielectric cable or a warm dielectric cable.
Cold dielectric HTS cables have an ohmic resistance of about 0.1 milli-ohms per kilometer, and the inductance is about 0.06 mH/km. In contrast, normal PVC cables or XLPE cables have a conductor resistance that is a hundred times higher and an inductance that is five times higher.