Ageing characteristics of paper-insulated power cables

Most of the underground distribution cable in use in the United Kingdom is insulated by windings of paper tape which are impregnated with compounds of oil, wax and resin, in various proportions. The structure of this type of insulation is expected to deteriorate with time so that, even if the cable is mechanically undisturbed, the insulation may eventually be unable to withstand the applied electrical stress and the cable will fail. The author shows that under favourable circumstances a well-made cable may survive for several decades, but failures sometimes occur in cables only a few years old