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High Voltage co-axial cable

With the innovative high voltage co-axial cable capacities of several gigawatts can be transmitted over 100 km, for example to link wind power stations in the North Sea with storage power plants in the Alps. The core of the innovation is that outside the line no magnetic and electric fields are measured and that even in case of an incident the environment is not harmed by any cooling Insulation liquid.

Magnetic and electric fields in the environment are avoided by a coaxial configuration of the supply and return conductors, in other words by an internal and external conductor. This effect has been known for a long time; however, a technical implementation had not been possible due to the lack of a heat transfer from the hot internal conductor to the environment.

However, as of about 1950 so-called oil-filled cables were introduced which lead the heat away by pumping oil through the hollow internal conductor. Yet the potential of environmental damage by escaping oil in case of a cable rupture is enormous, as for dielectric reasons the oil must be kept at 10 bar. Furthermore, with this solution the environment is not free of magnetic and electric fields. With our high voltage co-axial cable the space between internal and external conductor is filled with stearin. The essential effect consists of the potential emergence of a natural convection in the heated and melted stearin, which enables a good heat transfer from the internal to the external conductor and from there to the environment. In case of a leakage of the cable, stearin will escape and, depending on the exterior temperature, solidify there in a limited distance. Leaking stearin causes relatively little damage to the environment, whereas the dielectric properties as insulator are excellent.

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