An Analogue Solution of Cable Heat Flow Problems [includes discussion]

Steady-state heat flow problems related to buried cables can be solved with a simple electric analogue. The soil is represented by graphite-coated paper, and the cables and sinks by fixed electrodes applied with silver paint or by movable copper cylinders. Regions with lower thermal resistivity (t/r) than the main soil body (duct banks, special backfill) are simulated by placing one or more extra sheets of graphite paper on the base paper in electric contact with it. Applications described include a duct bank problem and a double-circuit pipe-type cable placed in a rectangular box of sand. The load reduction caused by close spacing, the beneficial effect of sand backfill in poor soil, and the influence of ground water are discussed.