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In this paper, an extension of the previously published method for the calculation of the derating factors for cables crossing external heat sources is proposed. The extension takes into account the longitudinal heat flow in cable metallic screen. The proposed algorithm is illustrated in a numerical example considering a practical situation of a high voltage cable crossing a steam pipe. Index Terms-Ampacityderating, cable crossings, power cables. NOMENCLATURE Conductor or sheath cross-section, m . DF Ratio of the permissible current when taking into account the presence of crossing heat sources to the permissible current of isolated cable. Maximum permissible current of the rated cable when isolated, A. Thermal resistance of cable insulation per conductor, K m W. Thermal resistance between sheath and armor, K m W. Thermal resistance of cable covering, K m W. External thermal resistance of cable, K m W. Mutual thermal resistance between cable and heat source, K m W. Equivalent thermal resistance of cable, K m W. Total thermal resistance of cable, K m W. Thermal longitudinal resistance of a conductor, K m W. dielectric losses, per core, per unit length, W/m. heat rate in the rated cable at the reference temperature (usually 20 C), W/m. Heat rate generated by external heat source , W/m. Number of heat sources, crossing the rated cable. Laying depth of the rated cable, m. Laying depth of heat source , m. Location of the hottest point on the route of the rated cable( -coordinate) when several crossings are considered, m.

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