A Study on Propagation Characteristics Degradation of High Voltage Power Cables Insulation

Power cables are of great importance in power transmission and distribution systems. Terminations and joints are the basic accessories of the power cables. They are required to make connections between lines or to an electrical apparatus. The various aspects are considered while designing the cable terminations and joints because they must possess the same integrity as their associated cables while making the connection both all indoor and outdoor applications. In cable installation, shielded power cables require electrical stress control when terminated. When the insulation shield is removed from a cable, high potential gradients are concentrated at the cutback point, causing high electrical stress. Electric field enhancement at these points can produce local discharges that could lead to either flashover along the insulation surface or dielectric breakdown causing cable failure. Cable terminations are designed to eliminate the stress concentration at the screen termination to avoid the break-down of the cable. Insulation of cable and accessories may be defected or deteriorated in installation and in use. After laying tests a diagnostic measurement should detect faults and defects caused by transports and installation. Successful measurements give fingerprint for further diagnostics during the service of the cable system. Partial discharges are one of the major reasons for degradation of cable system insulations in service. Thus, partial discharge measurement is an important diagnostic tool. Also, we will explanation the impact of Moisture with electric field forms water trees inside the insulation which may turn into electrical trees. Electrical trees are formed by partial discharges inside insulation and they will eventually lead into a breakdown of the insulation. And will study the impact of water conductivity if their water leakage in to XLPE cable insulation to do grows water tree and then the electric tree.