Standards and insulation characteristics of oil-insulated transformers

THE STRENGTH of the insulation in transformers to resist various types of voltage stress is very important. The service and life of the transformer is partially dependent on the insulation strength, and in recognition of this fact standards for insulation strength long have been established. In the course of time improvements have taken place in design, new applications have been created, and more has been learned about the nature of stresses which arise in service. Service conditions, too, probably will change in the future, which will require changes in insulation requirements. Therefore it is natural that gradual changes in the standards, and additions to them, have taken place, with the result that sometimes they are not entirely consistent. It is desired in this paper to point out some inconsistencies and propose certain changes in the standards which might be given consideration.