The effect of nanoparticle surfactant polarization on trapping depth of vegetable insulating oil-based nanofluids

• Three different sized Fe3O4 vegetable-oil based nanofluids was successfully prepared.
• The trapping depth of the Fe3O4 nanofluids was investigated.
• A new model considering surfactant polarization was proposed to calculate the trapping depth of the nanofluids.

Nanoparticles can generate charge carrier trapping and reduce the velocity of streamer development in insulating oils ultimately leading to an enhancement of the breakdown voltage of insulating oils. Vegetable insulating oil-based nanofluids with three sizes of monodispersed Fe3O4 nanoparticles were prepared and their trapping depths were measured by thermally stimulated method (TSC). It is found that the nanoparticle surfactant polarization can significantly influence the trapping depth of vegetable insulating oil-based nanofluids. A nanoparticle polarization model considering surfactant polarization was proposed to calculate the trapping depth of the nanofluids at different nanoparticle sizes and surfactant thicknesses. The results show the calculated values of the model are in a fairly good agreement with the experimental values.