Optimization of cable terminations equipped with non-linear stress control tubes

A significant electrical field grading in HV cable terminations can be achieved by using stress control tubes (SCTs), obtained by adding a controlled amount of conducting fillers, as carbon black or silicon carbide, to polymeric insulating matrices. Nevertheless, no data can be found in the literature concerning the influence played by the SCT length, thickness and position around the cable termination on the grading performances of these accessories. The purpose of this paper is to investigate on such interesting aspects by evaluating the electric field distributions inside cable terminations characterized by different arrangements of the SCT. The numerical evaluations of the electric field are carried out by adopting a model based on the electroquasi-static approximation of Maxwell equations.