Partial Discharge Study on Surface-Modified Pressboard Insulation in Natural Ester Oils

Transformer insulation systems rely on both solid and liquid insulating materials to ensure reliability and proper functionality. Despite the use of nanoparticles (NPs) into liquid insulation to improve dielectric characteristics, challenges such as agglomeration and sedimentation restrict their practical utility. To address this issue, NPs are integrated into solid insulation, providing a more stable method for enhancing thermal and electrical performance. This study examines the impact of TiO2and ZnO NPs on the effects of partial discharge (PD) in oil-impregnated surface-modified pressboard insulations (SMPB). Pressboard (PB) samples were modified with 0.05 wt% and 0.1 wt% of NPs and subsequently impregnated with fresh natural ester oil (NEO) and mineral oil (MO) for comparative analysis. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) are employed to analyze surface morphology and NP dispersion. PD characteristics, such as partial discharge inception voltage (PDIV) and phase-resolved partial discharge (PRPD) patterns, are assessed in compliance with IEC 60270 and IEC TR 61294 standards. The impact of NP incorporation on electrical properties, specifically AC breakdown voltage (ACBDV) and AC conductivity, has been thoroughly examined. The experimental assessments involve SMPBs immersed in fresh NEO and MO, with results compared to those from unmodified pressboards in the same base oils. This comparative evaluation provides insight into PD behaviour and demonstrates the impact of surface modification on enhancing the dielectric performance of PB–oil insulation systems. The results indicate that the inclusion of nanoparticles significantly affects PD behavior, with TiO2and ZnO exhibiting different levels of PD suppression. The findings demonstrate the effectiveness of SMPB insulation in improving dielectric performance, presenting a viable method for enhancing the reliability and efficiency of transformer insulation.