The effect of molecular structure of dielectric fluids on their conduction and breakdown

Several synthetic dielectric fluids with significantly different molecular structures were investigated with regard to their conduction and breakdown behavior to determine the relation between these processes under DC and AC conditions. M&DBT, DTE, DINP, PXE, PFPE, and PPMS were the fluids studied. The results show a lack of correlation between the two processes. The presence of spectral structural features or of electronegative atoms such as fluorine appears to overshadow the influence of charge transport on electrical breakdown. The significance of these findings is discussed in the light of available information on the electronic and molecular structure of these fluids. Conductivity by itself is not a good indicator of the expected breakdown voltage levels. Although within a family of liquids such as aliphatic hydrocarbons higher conductivities lead to lower breakdown voltages, this relationship does not hold for fluids of different molecular structures