Cellulose Insulation in Oil-Filled Power Transformers: Part I - History and Development

摘要

Cellulose insulation has been the preferred choice for the solid insulation in power transformers, but not because it is the best. In fact, it would never have been the preferred material if it were not available in plenty from natural renewable source - soft wood. In 1939, G. T. Kohan of Bell Telephone Laboratories in New York wrote an article in AIEE Transactions on cellulose as an insulating material for various electrical applications: paper capacitors, paper-insulated power cables, telephone cables [1]. He observed, "Although the use of cellulose does not go back to the Garden of Eden as do some of its applications, it is nearly as old as the electrical industry itself." The same year, the annual consumption of cellulose insulation in the United States was estimated by Kohan at 18 million kg (40 million pounds). Since then, the annual consumption has increased many fold. Oil-filled HV power cables, condenser bushings, and power transformers consume gigantic quantities of cellulose insulation measured in millions of tons.