Rapid Transfer Matrix-Based Calculation of Steady-State Temperature Rises in Cable Ducts Containing Groups of Three Phase Cable

Abstract

This paper presents a heat transfer matrix and superposed thermal field-based method that can rapidly calculate steady state temperature rises in three-core cable groups laid in ducts. The temperature rise of any cable is a combination of self-reaction and interaction from other cables. A heat transfer matrix is formed by self-reaction coefficient and interaction transfer coefficient representing the thermal characteristics of the cable groups in ducts. The heat transfer matrix can be obtained by enough samples including temperature rise and cable losses based on numerical analysis, trial or commercial software. Rapid calculations can then be performed by simplify iteration of temperature-loss. Extraction of the transfer matrix using CYMCAP ampacity and temperature calculation software and application of the fast calculation method are illustrated and compared, confirming the feasibility and relative simplicity and accuracy of the fast calculation method. INDEX TERMS Power cables, heat transfer matrix, ducts, temperature rise, fast calculation method.

Simplified Model for Heat Transport for Cables in Pipes

“…The expressions for keff and the Rayleigh-numbers are as before, and average temperatures are used for the surface and pipe wall (4) - (7). For isothermal concentric surfaces, the temperature field in the gap is not determined when using (6) to account for the effect of convection on the heat flow.…”

“…Lu et al, [6], present a temperature field model of a cable group inside a duct applying FEA. References [7] and [8] present a heat transfer matrix and superimposed thermal field-based method for calculation of the steady state temperature rises in three-core cable groups laid in duct. de Leon examines in [9], among other parameters, the effect of the duct size on cable ampacity.…”

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