Reinforcement of power cables crossing thermally unfavourable regions

The highest conductor temperature of a buried power cable is often governed by the most unfavourable section of the cable route, e.g. the crossing of a street or of another cable system. It can be shown, that an essential inc rease of current ampacity can be achieved if air-filled pipes are used layi ng parallel to the cable cores or containing them, and if the ends of these pipes are led up to the soil surface and therefore interacting with the am bient air. For many street crossings, such pipes are used anyhow. By this, a self-supporting cooling system for hot spots in cable routes can be estab lished without neither cooling stations, nor pumps or fans. During low-load periods, this cooling system extracts heat out of the cable trench, so tha t thermal reserves are given for extreme summer temperatures as well as for overload operations.