Influence of Magnesium Oxide (MgO) Nanoparticles for High Voltage Direct Current (HVDC) Cable Insulation

This study discusses the development of enhanced insulating materials for High Voltage Direct Current (HVDC) cable insulations by reinforcing Low-Density Polyethylene (LDPE) with nanomagnesia (MgO) particles. The main emphasis of this work is to investigate the DC breakdown voltage performance of LDPE/MgO nanocomposites as a function of filler content. Increase in DC breakdown strength is very important for long-term reliability and safety of HVDC cable insulation. Besides electrical performance, tensile strength and morphological study were made as complementary studies to check the mechanical stability and quality of particle dispersion. The nanocomposites were fabricated using the melt-blending method, where 40 grams of LDPE was mixed with 1.25 wt.%, 2.5 wt.% and 5wt.% of nanomagnesia at 170 [°C] and 50 rpm (rotation per minute) using a Haake internal mixer. The resulting materials were hot-pressed into 1 mm thin films at 160 [°C] and 50 bar pressure. DC breakdown voltage tests were conducted on the samples to determine their breakdown voltage. Tensile testing was conducted for the mechanical property evaluation where the LDPE and 2.5 wt% MgO composite show slightly lower strain, indicating decreased ductility. Overall, the incorporation of MgO enhances stiffness but reduces flexibility and strain-hardening capacity, resulting in a stronger yet less ductile material. Scanning Electron Microscopy (SEM) was undertaken to complement the results, which included the dispersion quality of MgO particles and the filler interfacial bonding. Results indicated that nanomagnesia incorporation improved the DC breakdown voltage of LDPE, with the optimum value at 2.5 wt.% of MgO. At this loading, the material showed the strongest dielectric strength while retaining reasonable tensile properties. Thus, this study has proven that LDPE reinforced with 2.5 wt.% of nanomagnesia is a viable and efficient insulation material for HVDC cable applications at average of 40.1 [kV] compared to pure LDPE at 32.41 [kV].