A New Method for Calcualting Alternating Current Losses in Pipe-Type Cable Systems

Using electrpmagnetic field theory, formulas are derived for alternating current losses in power cables with solid conductors installed in pipes made of carbon steel (magnetic pipes). A comprehensive framework for evaluating these losses is developed based on the method of images. This method not only gives a mathematical framework for the solution of alternating current losses, but it also gives the underlying physical picture of effects contributing to these losses. Skin effect, proximity effect and losses due to the presence of the pipe are calculated separately. For the first time the increase of losses in the conductors, when the cables are placed in a magnetic pipe, are analyzed mathematically. Good agreement is obtained between the calculations and experimentally determined a.c.-d.c. resistance ratios for pipe-type cables with concentric stranded copper conductors.