The Viscosity and Dielectric Property of Insulating Oil for Oil-immersed Capacitors

This study investigates the performance characteristics of five synthetic insulating oils used in oil-immersed power capacitors: monobenzyl toluene (MBT), dibenzyl toluene (DBT), mixed M/DBT oil, Phenyl Ethyl Phenyl Ethane (PEPE), and 1,1-Diphenyl Ethane (1,1-DPE). Key parameters including kinematic viscosity, relative permittivity, dielectric loss factor, volume resistivity, and breakdown voltage were systematically evaluated. Results indicate significant differences in fluidity and electrical properties among the oils. PEPE exhibits lower low-temperature viscosity but higher dielectric loss factor, DBT and M/DBT possess higher relative permittivity and kinematic viscosity, and 1,1-DPE demonstrates superior breakdown strength but lower polarization rate. In contrast, benzyl toluene demonstrated superior comprehensive performance in kinematic viscosity, dielectric stability, dielectric loss factor, volume resistivity, and breakdown voltage. It ensures both excellent insulation strength and appropriate fluidity and dielectric properties, meeting the performance requirements for insulating oil in power equipment such as oil-immersed capacitors.