Mechanical and electrical engineering aspects of long-distance underground power transmission

The delivery of the power from remote power generation sites to urban centres is increasingly becoming a challenge for the power industry since the use of traditional power transmission technology, such as overhead cables, is a politically sensitive issue and alternative approaches are sought. This paper reports the findings of a feasibility study into long distance power transmission via small diameter underground tunnels, constructed using trenchless technologies such as horizontal directional drilling or microtunnelling. The study examines the suitability of AC or DC transmission for such underground tunnels, various cooling methods to remove the heat generated in the conductors from electrical losses, type of conductor to be used, and issues concerning conductor installation. As a result of this study a number of technical challenges have been identified that need to be overcome in order to make the method an economically and technically viable option.