Dielectric Loss of Transformer Oil-Based Nanofluids: Effects of Oil Temperature and Nanoparticle Concentration

摘要

Dielectric loss quantifies inherent dissipation of the transformer oil-based nanofluids (NFs), which determines the operating loss and aging rate of the insulation system. Our experiment on zinc-oxide/silica NFs shows that the dielectric dissipation factor (DF) increases linearly with increasing nanoparticle volumetric concentration ranging from 0.02 to 0.25 vol.% and exponentially with increasing temperature ranging from 20 to 90 degrees C. These tendencies are well explained and estimated by a model proposed based on the conduction loss and nanoparticle relaxation polarization loss. It suggests that the conduction loss is significantly larger than the relaxation polarization loss in the NFs, whereas the dielectric loss is predominantly determined by the conduction loss. The additional shift of the charge carriers caused by the high oil temperature and the aggregation of the nanoparticles on account of the high concentration of the nanoparticles influence the actual DF of transformer oil-based nanofluids.