Role of Metal Oxide Nano Particles in Improving Electrical, Dielectric and Thermal Properties of Polyethylene Nano Dielectric

摘要

The design of insulation for HVDC extruded cables is one of the most challenging issues, mainly due to the dependence of its dielectric properties on temperature, electric field distortion due to accumulation of space charge in the insulation. Polyethylene-metal oxide nanocomposites are used to achieve the space charge reduction, enhance the volume resistivity and also achieve higher dielectric stress withstand capability. Study of Electrical, Dielectric and thermal properties of Nano dielectric is very necessary to understand its long term performance and its reliability when used in HVDC extruded power cables. Nanoparticles such as MgO, SiO_2 and clay have been investigated as fillers in linear low density and low density polyethylene. Surface pre-treated nano sized metal particles were dispersed in a rheometer with low density polyethylene at 100 °C for 20 min and nanocomposites were prepared. The distribution and dispersion of the nanoparticles in the LDPE is determined by Scanning Electron Microscopy. Electrical, dielectric, thermal and mechanical properties were determined. The surface and volume resistivity of nanocomposites have increased by one order compared to neat LLDPE & LDPE samples. Inclusion of nano fillers in the polymer matrix resulted in deeper traps with increased trap density for both positive and negative charges. Nano dielectrics with SiO_2 metal oxide treated with PEMAH and Trimethoxy methyl silane (TMMS) have shown less decay rate and higher initial potential. Further 3% and 4% MgO treated with HDMS have shown better performance. Permittivity has increased with filler content while dielectric losses have increased with filler content and frequency. Higher surface discharge inception voltage of LDPE Nano composite suggests increased surface discharge resistance. The results are presented and discussed.