Three decades of progress in electrical insulation

The last 30 years cover a period marked by outstanding advances in certain areas of electrical insulation. This period begins with what might be termed the synthetic-chemical age and ends with the beginning of the space age. Specifically, the paper records briefly the progress made in the theoretical phase of the field, the development of new insulating materials, the revision of the electrical insulation temperature standards, and the application of insulating materials to power equipment. The progress made in the development of materials, many of which were unheard of 30 years ago, has been truly phenomenal. This has resulted in marked advances in the design of new equipment. A few of these advances in the power field are discussed. Progress made in insulation temperature standards has resulted in new revolutionary methods of rating insulating materials and systems of materials as used in electric equipment. This has enabled the electrical industry to take better advantage of the host of new synthetic materials developed during the period covered by this review. This period may be characterized as one in which research and development in the insulation-materials area has, in a marked way, stimulated radical advances in design, reliability, and performance of electrical equipment. No radically new advances were made in the theoretical phase of the field, but the gradual progress made in the underlying theories has contributed considerably to our understanding of dielectric phenomena, especially in the liquid- and solid-state areas.