Breakdown Voltage And Partial Discharge Inception And Extinction Voltage Variations In Mineral, Natural And Synthetic Ester Oils

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K M Mahesh Kumar, Dr. B Ramachandra


The power transformer is a crucial element in power system network. The oil provides the insulation and cooling effect to transformer for high voltages and temperature rises in conductors. The dielectric breakdown voltage test is a method to determining the amount of contamination in insulating oil. Usually the contaminant is water, but it can also be conductive particles, dirt, debris, insulating particles and the by-products of oxidation and aging of the oil. In this study, breakdown voltage variation of insulation oils which is used for high voltage equipment is investigated. Three types of oils such as petroleum based mineral oil and ester based natural and synthetic ester oil are used to determine highest breakdown strength as per IEC60156 standard. Also partial discharge experiments are carried out by modeling transformer insulation as pigtail specimen and impregnated in different oils individually and their inception and extinction voltage are determined to find their PD withstanding strength. From the experimental results it is found that ester based oil shows higher breakdown and partial discharge inception and extinction voltage compared to traditional petroleum based mineral oil.

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