Radial thermomechanical behaviour

The external core screen of the MV network cable contains lengthwise grooves. One of the reasons for the existence of these grooves is to provide an elastic bedding effect making it possible to absorb part of the expansion of the insulation, particularly when overloaded, which contributes to improving the radial thermomechanical behavior of the cable. Numerous thermal cycle tests were done on the different components and on the complete cable, either in the form of short samples in an oven, or on samples several meters long heated by the circulation of current in the conductor. The "conductor, insulation and core screens ensemble' is homogeneous and its radial expansions are reversible. These bring about a residual deformation of the aluminum screen/PVC ensemble leading to an increase in the diameter and a reduction in the overlapping width of the aluminum screen perceptible especially above 120 C conductor temperature. The slackness effect thus created at high temperature may lead to a loss of the lengthwise water tightness of the cable.