Influence of electronic scavenger additives on AC breakdown voltage of synthetic ester
Résumé
This study deals with the influence of two kinds of electronic scavenger additives/compounds, namely methyl iodide (iodomethane), CH3I, and carbon tetrachloride CCl4 on the breakdown voltage (UBDV) of MIDEL 7131 synthetic ester (SE). The tests are conducted under 60 Hz AC voltage according to the IEC 60156 standard, for various concentrations of additives ranging 0-600 ppm. Statistical analysis is performed to check whether the experimental data obey the most used probabilistic distributions for electrical BDVs, namely normal and Weibull laws. The estimation of the BDV with risk probabilities of 1 and 50% are also deduced. It is shown that the average BDV of SE increases with the concentration of both additives up to an optimum value beyond which it decreases; the optimum concentration for both cases is 400 ppm. The improvement of the average UBDV is about 27% with CH3I and 21% with CCl4. The values of UBDV conform to Weibull distribution with CH3I; it is also the case with CCl4, except for 200 ppm.