Characteristics of insulating oil for electrical application

Paraffinic crude oils are known to contain significant amounts of wax that, if not removed, could provide an insulating oil having a high pour point which could interfere with the low temperature functioning of most electrical equipment. Because of the wax problem, it was necessary to study the behavior of the paraffinic base insulating oil in representative production size equipment, such as tap changers and power circuit breakers, to be sure that the equipment would operate if exposed to temperatures as low as 40 C. Other studies, such as material compatibility, lubricity of the new oil, arc formed gas, response to dielectric breakdown levels represented in large power transformers, and accelerated aging in distribution transformers, were important to ensure full acceptance of a replacement oil. The work in this project was separated into different phases in order to provide a broad study of the new type of insulating oil. This evaluation of experimental oils indicated that paraffinic transformer oils as a class can provide useful supplements or replacements for naphthenic oils.