Electrically induced pressure under switching operation and mechanical tensile strength as a new measurement tool of cable aging

The study at aging has been carried out by many authors. Most of these studies relate the formed tree length with new branch with time. Also some of these studies relate applied voltage with breakdown voltage with time. In the present paper the author aimed the tree initiation as a pressure dependent mechanism. The tree starts at a defect point of protrusion tip. The electric field at these defect sites may reach very high values. The square value for the ratio of intrinsic electric stress of given dielectric medium to the operating applied electric field intensity at switching level value represent a main part of determining the age of a cable. Also the thickness of insulating material and the length of each step determines another part of cable age, especially for thicknesses larger than 1.12 mm