Behavior of HV cable at short circuit: Part II

Article [1] studied behavior of an HV cable at load arcing events when the shield at the power supply side was grounded, and at the load side it was floating. It was shown that the transmission line model was no longer applicable, and that the cable insulation was overvolted at the load end. Maintaining a simplicity of a two-wire line approximation it was still possible understanding most important phenomena of the load breakdown in unterminated shield connection. However, the period of oscillations T for this case was almost four times greater than could be expected from the cable electrical length! The discrepancy was not emphasized in [1], and, to the best of our knowledge, was not explained in literature. In Part II, we analyze the reasons for the remarkable increase of T. We use lumped circuit simulation and experiments on model lines. The first shows that because the currents in the central conductor and the shield flow in the same direction, the issuing circuit inductance is much greater than that in a conventional line discharge. These inductances have been assessed. Experiments proved that the cable and ground layouts have also large impact on T. Experimental results and simulation agree well.