Non destructive testing of high voltage cables by non-electrical methods

Today, many electrical methods such as partial discharges detection and high voltage breakdown tests yield fruitful information on power cable insulation quality and have been performed by most manufacturers as quality control tests. The authors have investigated the capability of conventional nondestructive testing (NDT) methods to detect these defects just after processing, i.e., before the metallic shield and the polymeric jacket are added to the cable. Three methods have been investigated: X-ray tomography; ultrasonic testing; and thermography. The three methods were tested on high voltage cables in which artificial defects were previously inserted. These defects simulate voids and metallic contaminants. The first step of investigations was carried on defects with a size of at least 300 μm. In this paper, the three methods are presented and discussed. The results obtained are then detailed as well as the possible applications of these techniques for processing, quality control and qualification purposes