Development of Insulating Oils

During the last 35 years or more the development of insulating oil for use in transformers, circuit breakers, etc., has paralleled the development of electrical apparatus. Various steps in the development of oils for this purpose are described in the paper. These include the discoveries from time to time of elements which have been responsible for difficulties which arose in the use of such oils. These include such items as the effect of moisture, the importance of flash and fire test values, the question of fluidity for better cooling, the development of oils with non-sludging characteristics, and a statement of the long series of tests and experiments necessary to eliminate these various difficulties. The importance of a universal oil for insulating purposes is stressed and some of the conflicting characteristics for different uses are described. Attention is called to the selection of the proper raw materials from which insulating oil is derived, together with the extreme care which has been found necessary in the handling of containers, in making shipments, and in applying oil to specific purposes. While much has been accomplished in the securing of satisfactory oil, it is intimated that research and development must be more or less continuous so long as the electrical art advances and oil is used for insulating purposes.