A study on the dielectric response of polyethylene-metal oxide nanocomposites for electrical insulation in HVDC cables

Abstract

Abstract Metal oxide nanoparticles such as MgO and SiO2 have been investigated as fillers in low density polyethylene. The surface modification of the oxide nanoparticles were done with functional methyl, ethyl, hexadecyl or octylsilane. The distribution and dispersion of the nanoparticles in the LDPE is determined by SEM (Scanning Electron Microscopy). Studies were carried out by measuring surface resistivity, volume resistivity. Fourier Infrared spectrometer for identifying the functional groups. Dielectric response studies were carried out using spectroscopic techniques like Dielectric spectroscopy (dielectric loss angle, permittivity, capacitance measurements as a function of frequency from few mHz upto 1 kHz). The surface and volume resistivity of nanocomposites have increased by one order compared to neat LDPE samples. Higher concentrations of nanoparticles have resulted in lower withstanding stresses probably due to decrease in crystallinity with filling concentration. TMMS treated nanoparticle composite show better performance compared PEMAH treated nanocomposite. The dielectric response study on nanocomposites show there is no change in permittivity upto 1 Hz, but slightly increase in value below 1 Hz and upto 0.001. It is presumed that large amount of charges migrate into and go through the LDPE. On the contrary Nano composites can inhibit the charges to inject into the interior of the composite and make most of the charges gather on the surface of the sample.