Mechanistic Study of External Electric Field Effects on Insulating Oil in Power Capacitors Based on Molecular Simulation

Benzyl toluene (M/DBT), owing to its exceptional physical and electrical properties, serves as an ideal liquid medium for power capacitors. This study systematically investigates the influence mechanism of external electric fields on the microstructure and insulation performance of M/DBT by constructing molecular models and employing molecular simulation techniques. Results demonstrate that as the external electric field strength increases, the total energy of M/DBT molecules decreases, while the dipole moment and polarizability rise significantly, leading to reduced molecular stability. Under electric field-induced tensile forces, molecular chains undergo geometric deformation, with C-H bond elongation further weakening structural integrity. At extreme field strengths (MBT: 20.41 V/nm, DBT: 13.57 V/nm), irreversible structural damage occurs due to chemical bond fracture. Additionally, the frontier orbital energy gap (Eg) narrows with increasing field intensity (MBT: 3.28 eV→1.33 eV), significantly enhancing molecular reactivity and conductivity. Infrared spectroscopy reveals notable shifts and intensity variations in high-frequency absorption peaks, consistent with bond-breaking phenomena. This study elucidates the micro-degradation mechanism of M/DBT insulating oil under external electric fields, providing a theoretical foundation for material modification, high-voltage breakdown threshold prediction, and non-destructive insulation status assessment.