Canals as cable routes

An investigation into laying cables in canals showed the thermal resistivity of the silt to be as high as 118 cmdegC/W. This high value led to the investigation of the laying of cables on posts in free water. The possibilities of uncontrolled silting and algae growth suggested a more conservative approach by laying cables in troughs on the towpaths. This method, using different filling mediums, was thoroughly examined experimentally, and found to be so satisfactory as to allow two 275 kV, 760 MVA circuits to be installed in a 4ft 6in-wide trough without water cooling. Savings in the overall contract cost are expected using this technique, which, it is believed, may be extended to areas around substations and alongside motorways or railways. An analysis is presented which takes account of the increase in temperature of the ground surface where cables are laid at shallow depths.