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Transformer oil or insulating oil is an oil that is stable at high temperatures and has excellent electrical insulating properties. It is used in oil-filled transformers, some types of high-voltage capacitors, fluorescent lamp ballasts, and some types of high-voltage switches and circuit breakers. Its functions are to insulate, suppress corona and arcing, and to serve as a coolant. ==Explanation== The oil helps cool the transformer. Because it also provides part of the electrical insulation between internal live parts, transformer oil remain stable at high temperatures for an extended period. To improve cooling of large power transformers, the oil-filled tank may have external radiators through which the oil circulates by natural convection. Very large or high-power transformers (with capacities of thousands of kVA) may also have cooling fans, oil pumps, and even oil-to-water heat exchangers.〔Kenneth R. Edwards, ''Transformers'', American Technical Publishers Ltd., 1996 ISBN 0-8269-1603-1 pp.138-14〕 Large, high voltage transformers undergo prolonged drying processes, using electrical self-heating, the application of a vacuum, or both to ensure that the transformer is completely free of water vapor before the cooling oil is introduced. This helps prevent corona formation and subsequent electrical breakdown under load. Oil filled transformers with a conservator (oil reservoir) may have a gas detector relay (Buchholz relay). These safety devices detect the buildup of gas inside the transformer due to corona discharge, overheating, or an internal electric arc. On a slow accumulation of gas, or rapid pressure rise, these devices can trip a protective circuit breaker to remove power from the transformer. Transformers without conservators are usually equipped with sudden pressure relays, which perform a similar function as the Buchholz relay. The flash point (min) and pour point (max) are 140 °C and −6 °C respectively. The dielectric strength of new untreated oil is 12 MV/m (RMS) and after treatment it should be >24 MV/m (RMS). Large transformers for indoor use must either be of the dry type, that is, containing no liquid, or use a less-flammable liquid.It is highly recommended Recently, research is underway in making transformer oil nano fluids by mixing insulating or semiconducting particles with transformer oil to enhance its thermal conductivity and electrical breakdown strength. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Transformer oil」の詳細全文を読む スポンサード リンク
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