Ratings of cables in tunnels-the HEA(R)T of the matter

A wide variety of installation arrangements have been employed for cables in tunnels. The type of arrangement can involve the cables installed in air, in troughs or buried in the tunnel floor and can include some method of forced cooling. Examples of different installation conditions are: buried; in air; naturally cooled; and forced cooled. The type of installation employed has a significant effect on the rating that can be achieved for a given cable. This effect is illustrated with a table showing the rating for a 400 kV 2600 mm² Cu conductor, paper insulated, fluid filled, CSA sheathed cable installed in different arrangements