Ferrofluid effect in mineral oil: PDIV, streamer, and breakdown voltage

Ferrofluid is a colloidal liquid made of magnetite nano-particles coated by a surfactant, and blended in a liquid substance. Regarding transformer insulation, small amounts of ferrofluid improve oil performance, particularly as regards the breakdown voltage during positive lightning impulse. Indeed, the performance of colloidal liquids based on ferrofluid and oils having different humidity levels has not been investigated thoroughly. Also, the influence of ferrofluid on partial discharge inception has not been reported in detail. Therefore, breakdown voltage and partial discharge inception tests were carried out using oils with different moisture and ferrofluid concentrations. The results show that ferrofluid does not affect appreciably partial discharge inception, but can be beneficial for streamer propagation and breakdown voltage.