F.P. Dawalibi, J. Liu, S. Fortin, S. Tee, and Y. Yang (Canada)
Electromagnetic fields, pipe-type cable, steel casing, overheating, eddy currents, and power system operation
This paper discusses the analysis of an overheating problem which has been observed within a 140' (43 m) long steel pipe casing containing 115 kV three-phase electric power cables. A steel casing electromagnetic field model has been built to determine the induced current (eddy currents) distribution along the radial, transverse, and longitudinal directions of the casing caused by the energized cables under different operating conditions. This model takes the combined effects of the inductive, conductive, and capacitive interference into account. This study involved a circuit model to determine the voltage and current distributions in the conductors of the buried power cables. Furthermore, a detailed analytical model of the cylindrical steel casing (assuming an infinitely long casing) was conducted to determine the actual paths of eddy current flow and their density throughout the cross section from the inner surface to the outer surface of the steel casing. The computation results show that induced currents in the steel casing can cause significant heat losses and that the exact distribution of the induced current density within the steel casing plays a crucial role in the heat losses generated by such currents.
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