A comparison of the electrical breakdown characteristics of hydro- and fluorocarbon liquids

Structure–Activity Relationship Models to Predict Properties of the Dielectric Fluids for Transformer Insulation System

“…As dielectric insulating liquids, a high dielectric strength to withstand electrical stresses is the most important property for the operation and performance of a transformer. By carefully reviewing all the experimental work carried out [ 18 , 19 , 20 , 21 , 22 ], it appears that significant discrepancy exists among the experimental results reported by different investigators. The experimental electrical properties were obtained in liquids containing various kinds of unavoidable impurities, leading all electrical properties of dielectric liquids so far to be extrinsic rather than intrinsic [ 18 , 19 ].…”

“…The pulse technique may reduce the effect of space charge so that the measured breakdown strengths are higher than those measured using DC/AC voltages. Three types of experimental data at ambient temperature and pressure were collected to serve as the training sets: (1) the electric strengths for 12 saturated ( n -pentane, n -hexane, n -heptane, n -octane, n -nonane, n -decane, n -tetradecane, 2-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, 2,4-dimethylpentane, 2,2,4-trimethylpentane) and 7 aromatic (benzene, methylbenzene, ethylbenzene, n -propylbenzene, isopropylbenzene, n -butylbenzene, ter-butylbenzene) hydrocarbon liquids measured by applying a single pulse of voltage breakdown with the duration time of 1.65 microseconds to the liquid between hemispherical stainless-steel electrodes spaced 0.051 mm apart [ 18 , 19 , 20 ], (2) the electric strengths for 8 hydro- and fluorocarbon liquids ( n -pentane, perfluoro- n -pentane, n -hexane, perfluoro- n -hexane, methylcyclohexane, perfluoro-methylcyclohexane, dekalin, perfluorodekalin) measured with electrodes spaced with a gap length of 0.15 mm in the uniform field [ 21 ], and (3) the electric strengths for 9 liquids (e.g., alkanes, benzenes, alcohols, CCl 4 ) measured with electrodes spaced with a gap length of 0.2 mm and a pulse duration of 4.5 microseconds [ 22 ]. The experimental E P data, with a total of 36 molecules, are listed in Table S1 in the Supplementary Materials .…”

“…The flash point per the ASTM D93 method is an important criterion for the fire and explosion hazards associated with transformers [ 29 ]. A total of 37 experimental closed-cup flash points were chosen in the present work to develop the SAR model [ 20 , 21 , 22 , 25 , 26 ]. All five descriptors and the experimental data are listed in Table S3 .…”

“…A total of 33 liquids covering both mineral oils and esters were employed to develop the SAR model for the dielectric constants in a unified manner [ 20 , 21 , 22 , 25 , 26 ]. As shown in Figure 6 and Table S4 , the dielectric constants are in the range of 1.8–3.0 and catalogued into three classes in the following order: esters > aromatic hydrocarbons > saturated hydrocarbons.…”