Effect of Nano Fillers on Dielectric Properties for the Crosslinked Polyethylene High Voltage Cables

Abstract

Electrical insulators play a key role in every electrical power system (sub-stations, distribution and transmission lines). Theoretically, an electrical insulator provides very high resistance and protection for the electrical equipment so that no current can flow through it. Polymer insulators are used for both distribution and transmission lines. Since 1970, the use of such insulators increased rapidly because of their advantages of light weight, high mechanical strength, easy handling, maintenance free, and considerably low cost. Insulators are required in the power system network to provide ground isolation and mechanical support for line conductors. Different kinds of insulators are being utilized in the transmission lines and substations. Many power utilities are now using non-ceramic insulators like XLPE composite insulators. Crosslinked polyethylene XLPE is widely used in medium and high voltage cables insulation due to its low dielectric losses and its ability to improve cable properties in high temperatures. Also, XLPE has an excellent chemical resistance. Due to the various advantages, the XLPE-insulation type has vastly displaced the traditional classic paper-insulated types in many sectors for cables. Many studies and researches have been conducted to improve XLPE characteristics. This thesis aims to develop XLPE nanocomposites for usage as power cables insulations in the industrial applications. To attain this, XLPE polymer were blended with different fillers of Titanium Dioxide (TiO2) and Zeolite (Z) nanoparticles: 0, 1, 3, 5 and 7 weight percentages (wt%). The dielectric properties of these developed XLPE nanocomposites were studied by measuring the AC breakdown strength with a regulated high voltage testing transformer (50Hz). The breakdown strength of the nanocomposites is tested in several conditions such as: different temperatures ranges (30℃ and 250℃), nanocomposites were thermally stressed for 24 hrs aging in high temperatures (120℃ and 160℃), low saline water and high saline water conditions. The mechanical properties such as tensile strength and elongation at break were also assessed. The thermal properties of nanocomposites were examined using Thermo Gravimetric Analysis (TGA). Addition of nano TiO2 with 5 wt% showed the optimum results to improve the electrical, mechanical and thermal characteristics of XLPE nanocomposites compared to Z nanofiller.