Calculation of steady-state temperature rise of water-cooled buried cables using a new iterative method

Abstract

The paper describes a new iterative method for calculating the steady-state temperature rise of water-cooled cables buried in a homogeneous soil. Cables and water pipes are represented by line heat sources and sinks of variable magnitude and position, and a computer program is used to calculate the necessary magnitudes and positions of the heat sources and sinks needed to represent the temperature distribution accurately. Open boundaries are used, and this avoids possible errors resulting from the usual practice of imposing isothermal surfaces at finite distances from the cables. It allows a check to be made on boundary conditions used for relaxation calculations or electrolytic-tank measurements. However, the method of analysis described here is considered superior to relaxation for calculating cable temperature rise in a homogeneous soil. A detailed example is given of a calculation carried out at one point in a cable run, including the complete temperature distribution in the soil. A technique is then outlined for applying the method at various points along a cable run, and consequently for calculating the rate of water flow required to maintain an acceptable conductor temperature.