Comparison of statistical breakdown voltages in jatropha curcas methyl ester oil and mineral oil under AC voltage

Abstract

Due to their dielectric strength, viscosity and oxidation stability, mineral oils have been used for more than one hundred years ago as insulation liquid in high voltage equipment. However, mineral oils are non-renewable materials and have a low level biodegradability; their level of biodegradability is not more than 30 %. For that purpose, the development of vegetable oils is being continuously performed by many researchers and industries to replace mineral oils. These natural products present a high biodegradability, non-toxicity and higher fire safety guarantee. In general, vegetable oils which have been used today are derived from food material such as soybeans, palm, corn, sunflower and others. In this paper, we first introduce a new vegetable oil derived from a non-food material we called “JMEO (jatropha curcas methyl ester oil)”. JMEO is produced by alkaline esterification process of jatropha curcas oil which comes from the pressing of jatropha fruits. Jatropha curcas are non-edible crop that can grow in all types of soil in tropical and subtropical regions and even in barren soils with low rainfall. Moreover, these plants do not need much fertilizer. Then we present the results of a comparison of statistical AC breakdown voltage in JMEO and mineral oil (naphtenic type). Breakdown voltage (BDV) measurements have been performed on series of 40 tests basing on IEC 60156 Standard. Hypothesis test of conformity to normal distribution of BDV is carried out by applying Shapiro-Wilk tests to calculate W-value and P-value and skewness and kurtosis test. We mainly analyze histogram, probability of oil samples, mean and standard deviation. It appears from the obtained results that the BDV of JMEO is better than that of mineral oil. Thus, JMEO (jatropha curcas methyl ester oil) constitutes a potential liquid for replacing mineral oil in high voltage equipment and especially in high voltage power transformer.