First-Hand:Westinghouse Pioneers Development of Sulfur Hexafluoride (SF6) Circuit Breakers

Submitted by Winthrop Leeds

In an interesting quirk of fate that my life was affected in three important ways by a man whom I never met or even saw. This was Benjamin Garver Lamme, chief engineer of the Westinghouse Electric Corporation, who was responsible in his earlier years for the design of the first electric generators installed at Niagara Falls.

In my junior year in high school when I was deciding which college I should attend, my attention was drawn to the remarks of Mr. Lamme published in the September, 1921 issue of the Journal of the AlEE. His remarks were in response to a questionnaire submitted to one hundred prominent electrical engineers asking for suggestions to improve the college trained engineer.

He wrote, "As an indication of how little we care for the student's knowledge as a whole, I may say that in reviewing the selected college graduates for our work here, we ask them almost nothing about their work in general. We simply endeavor to find out their aptitudes, characteristics, analytical abilities, use of mathematics and how well they can use their heads." This confirmed my predisposition to attend a small liberal arts college as a foundation, with possibly a year of graduate study in a large institution to bolster my technical knowledge.

In 1937, I was awarded the Lamme Scholarship. This was given by Westinghouse for a year of graduate study to a promising young engineer at a school of his choice.

My boss, John B. MacNeill, suggested that I couldn't do better than to attend his alma mater, the Massachusetts Institute of Technology for graduate study.

In 1961, I was given the responsibility of managing the entire power circuit breaker engineering department. However, I found that handling personnel problems, union disputes, and budgetary limitations was not my "cup of tea." I was happier two years later when I was put in charge of a new section-New Product Development. This made it possible for me to supervise the group of engineers that produced the record-breaking 500 kw SF6 circuit breakers, which I consider my highest achievement. Throughout my career until his retirement, I considered J. B. MacNeill to have been my mentor.

The climax of my career was the application of the gas SF6 (sulfur hexafluoride) to high voltage switchgear, including the first 500 kw circuit breakers put into service in the United States. It all started with our attempts to answer customers' urgings to find a nonflammable substitute for oil in the design of high power circuit breakers.

Mr. H. J. Lingal, our then Power Circuit Breaker Engineering Manager, suggested that our long range development group systematically test various gases of known high dielectric strength that might possibly do the job. Two of my engineers, Dr. T.E. Browne, Jr., and Albert Strom, carried out such a series of arc rupturing tests.

When they got to SF6 they were astonished to find that it had remarkable arc interrupting ability. It was first tried out with low-power devices, such as load-break disconnecting switches for high voltage, and circuit breakers for large capacitor bank switching. Success with this equipment led to higher power circuit breaker applications. Plain break interrupting ability was dramatically improved by using a piston to pump the SF6 gas through arcs drawn at separating contacts. Eventually, the highest power breakers were successfully developed using a compressed gas system that would release a very strong blast of gas for effective high power arc extinction.

Naturally, this development took quite a number of years, studying the effect of arcing on the gas, the application of filters and dryers, selecting suitable insulating materials and so on. I followed this work closely and spent considerable time with our sales people and customers in educational efforts to acquaint them with the advantages of this unfamiliar medium, SF6. Bob Lawrence reported to me several years later that in a meeting considering my nomination for the Lamme Medal, the chairman, Mr. A.C. Monteith, referred to me as "Mr. SF6"!

As time goes on, the advantages of using SF6 in place of oil have become so apparent and used so widely that it has become an industry standard. However, it appears that the pioneering efforts of Westinghouse in introducing the use of SF6 in arc interrupting devices have been largely forgotten. Nevertheless, the fundamental Lingal, Browne, and Strom patent #2,757,261 issued on 7-31-56 with a filing date of 7-19-51 gives a complete story of the earliest experiments switching arcs in an atmosphere of SF6.

In 1971, a year after my retirement from Westinghouse following a forty-four year career in one field, the design and testing of high voltage power circuit breakers, I was presented with one of the IEEE prestigious awards, the Benjamin Garver Lamme Gold Medal.

The citation read, "For contributions to the development of high voltage high power circuit breakers, specifically using SF6 gas, and for his effective exposition of the theory of arc interruption. "

During my career, I advanced through the membership grades, becoming eventually a Fellow and Life member in IEEE. I prepared seventeen transactions papers, including a national prize paper in 1943 with L. R. Ludwig, co-author. My only national office assignment was Chairmanship of the Research Committee, 1958-1960.