Design, experimental validation, and multi-physics modelling of functionally graded nanodielectric insulation for enhanced HVAC and HVDC cable reliability

This study investigates functionally graded nanodielectric (FGND) insulation based on magnesium oxide (MgO) and graphene oxide (GO) incorporated into a cross-linked polyethylene (XLPE) matrix. The experimental work is based on graded MgO/GO-reinforced XLPE compared with neat XLPE and SiO₂-filled XLPE, whereas other nanofiller systems are studied separately through computational and PSO-based analysis. An electro-thermal coupled charge-transport model is developed to simulate charge dynamics and electric-field redistribution, supported by experimental electrical, thermal, and multi-stress aging characterization. The graded design and PSO analysis are used to optimize the concentrations and spatial distributions of MgO and GO. The measured maximum electrical-tree length decreases from 780 to 165 μm, while the peak space-charge density decreases from 50.2 to 8.2 C/m3 for the neat XLPE and MgO/GO-based FGND systems, respectively. The dielectric strength increases from 285 to 435 kV/mm. The measured experimental endurance coefficient increases from 9.1 to 18.5, while the service-life estimate exceeding 70 years is obtained through Inverse Power Law extrapolation. The measured space-charge density and endurance coefficient are compared with the corresponding theoretical predictions of 8.5 C/m3 and 18.8, respectively. Graded MgO/GO-reinforced XLPE has potential to improve dielectric performance and aging resistance under the investigated HVAC and HVDC conditions.