Dielectric Performance of Sustainable Fluids

Early studies discovered that the streamer breakdown voltage and breakdown acceleration voltage in selected ester fluids were lower than those in mineral oil (MO) in a nonuniform electric field under lightning impulse voltage [1]. In the present work, the dielectric performance of sustainable fluids (e.g., synthetic esters, natural esters, and isoparaffinic oils) was systematically investigated and compared with MO. Five types of electrode configurations (viz., needleplane, needle-sphere, plate-plate, a U-type geometry, and a turnturn-turn model) were introduced to understand further the features of streamers and breakdown. The permittivity, dissipation factor, and resistivity of fluids were measured and compared at
${90^ \circ }\mathrm{C}$
from 0.001 to 10000 Hz . Cole-Cole plots were drawn at
$20{\;^ \circ }\mathrm{C}$
from 0.00001 to 10000 Hz for the first time in seeking the possible mechanisms of polarization. Breakdown voltage and the locations of breakdown in a transformer-like turn-to-turn geometry were recorded and analyzed under AC voltage and a chopped-impulse voltage. The investigations enable us to achieve a sustainable insulating system for the potential application in the next generation of HV transformers.