Investigation of conflicting cable-sheath loss formulÿ

Formulÿ for calculating the eddy-current loss in the bonded sheaths of single-conductor cables have been published in the I.E.E. Journal. These contain a term log [(1¿K)/K] instead of the usual term log (1/K) used by most authors in formulae for this purpose, namely those published in the Electric Journal. These two terms are caused by using different limits in integrating the conductor flux, thereby producing quite a difference in the results obtained by the two methods. The present author has carried out an investigation by working out a practical example, using an independent method, with a view to determining which formula is correct. The results of this investigation show that for close or practical spacing the formulae published in the I.E.E. Journal give a result too low and also that the term log[(1¿K)/K] should be changed to log (1/K)