Oral-History:Aage Pedersen

About Aage Pedersen

A. Pedersen was born in 1921, in Odense, Denmark. He attended local school and then entered the Technical University at Copenhagen in 1941. At university he studied physics and electrical engineering. He graduated in 1948 after interruptions caused by World War II. In 1949 Pedersen took a study tour of Holland and England, and won a two-year scholarship to the University of Liverpool, where he studied electrical discharges with high voltage equipment. In 1953 he returned to Denmark and taught at the Technical University. In 1956 Pedersen went to work for the English Electrical Company, which was then England's largest manufacturer of power equipment, and oversaw high voltage transformer testing. Pedersen then accepted a job offer from ASEA, and moved to Sweden to work on rotating high voltage machines and research epoxy insulation of generator windings. In 1961 he returned to the Technical University in Copenhagen to teach applications of physics to power engineering, and continued consulting for ASEA. Pedersen supported international cooperation for power engineering research, and attended conferences across the globe. He was involved with IEEE from the organization's founding, and became a Senior Member in 1966. He has many publications in the IEEE Transactions and became an IEEE Fellow in 1984.

The interview spans Pedersen's career in power engineering, beginning with his university education and closing with his retirement and continued research in the field. Pedersen discusses his work with high voltage equipment, particularly with power generator design, transformer insulation, rotating machines, and surge voltages in transformer windings. He describes his work with other colleagues in the field, and recalls some of his international travels and contacts. Pedersen discusses his work at the University of Liver pool, the English Electric Company, ASEA, and the Technical University of Denmark. He surveys his IEEE activities, including publications and meetings. The interview closes with Pedersen's suggestions for training present-day power engineers.

About the Interview

AAGE PEDERSEN: An Interview Conducted by Frederik Nebeker, Center for the History of Electrical Engineering, 12 August 1994

Interview #230 for the Center for the History of Electrical Engineering, The Institute of Electrical and Electronics Engineers, Inc.

Copyright Statement

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Request for permission to quote for publication should be addressed to the IEEE History Center Oral History Program, IEEE History Center, 445 Hoes Lane, Piscataway, NJ 08854 USA or ieee-history@ieee.org. It should include identification of the specific passages to be quoted, anticipated use of the passages, and identification of the user.

It is recommended that this oral history be cited as follows:

Aage Pedersen, an oral history conducted in 1994 by Frederik Nebeker, IEEE History Center, Piscataway, NJ, USA.

Interview

INTERVIEW: A. Pedersen

INTERVIEWER: Frederik Nebeker

DATE: 12 August 1994
PLACE: Lyngby, Denmark

[Editing and footnotes courtesy of A. Pedersen's long-time colleague and friend Dr. Iain McAllister of the Department of Electric Power Engineering at the Technical University of Denmark.]

Family Background and Education

Nebeker:

I'm talking with Mr. Aage Pedersen, at his office at the Technical University of Denmark. This is Rik Nebeker and it is the 12th of August 1994. You were born in 1921?

Pedersen:

1921, yes.

Nebeker:

In Odense?

Pedersen:

In Odense, yes.

Nebeker:

Did you go to a Gymnasium?

Pedersen:

No. My parents were very poor, and there was no academic tradition in my family. But I did very well at the local school, so the headmaster there persuaded me that I should not do like they had all been doing in my family — learn a craft —

Nebeker:

A trade, yes.

Pedersen:

Trade, but try to get a higher education. But there were very few Gymnasiums in those days.

Nebeker:

Right.

Pedersen:

It was impossible for me to get access to any, and my parents could not afford any private tuition. But I was very fortunate in 1939 or 1940. The special private evening classes were held in Odense, where you could prepare yourself for a special entrance exam for the Technical University.

Nebeker:

That wasn't the usual way of getting admittance to it?

Pedersen:

That was one way you could get admittance, and this dates back to Ørsted. He got the idea that it should not be restricted just to those coming through the normal channels.

Nebeker:

I see.

Pedersen:

So I got this special entrance exam, and I could start here in 1941.

Nebeker:

So you had prepared especially for that exam?

Pedersen:

Yes, and I had to pass an exam here in the summer of 1941.

University Study During World War II

Nebeker:

I see. How did the war affect your schooling?

Pedersen:

The first two years, hardly any effect, apart from [shortages of] everything, of course.

Nebeker:

You mean 1939 to 1941?

Pedersen:

I stayed in Odense until 1941.

Nebeker:

Right.

Pedersen:

There I had no problems. I went to Copenhagen in 1941. I had never been away from Funen (Fyn).

Nebeker:

Is that right?

Pedersen:

It was a fantastic experience for me. I started studying chemistry here. I was really interested in physics, mathematical physics. I had been told that one well-known Danish professor, Torkild Bjerge, who was professor of physics at D.T.U. in those days, started by studying chemical engineering. So I said, "Well, if he can end up as a physicist, so can I." So I started. But I soon became disinterested in chemistry. There was too little mathematics, too little physics. So I was allowed to transfer to electrical engineering after the first semester here.

Nebeker:

I see.

Pedersen:

In those days, studying here for a degree in engineering was quite different from today. It was split up in two parts, and part one was a normalized study time of two years. You were allowed to study only two subjects, mathematics and physics. No engineering. When you had passed a rather strict exam after two years in physics and mathematics, you could start engineering.

Nebeker:

I see.

Pedersen:

But there was another request. If you wanted to be an electrical engineer you had to spend one year as an apprentice in industry. So 1943 to 1944 I spent in Odense, as an apprentice.

Nebeker:

What company did you work with?

Pedersen:

Thomas B. Thrige which is today called Thrige-Titan, and also the telephone company at Funen.

Nebeker:

What did Thrige produce?

Pedersen:

They produced transformers and rotating machinery, so it was in the line of business. There I became very interested in the physical and mathematical background for construction and the design of rotating machines and transformers. I was hooked to power engineering from that. Else I had intended to go in for electronics.

Nebeker:

I see.

Pedersen:

But I could see that fundamentally there were so many interesting problems referring to classical physics in power engineering that I decided to go in for power engineering.

Nebeker:

In the design of rotating machinery? Transformers?

Pedersen:

No, the general background. In those days we could study in a field which was called general electrical engineering. If I translate directly from Danish, almen elektroteknik in Danish. At German universities they had a similar line called, in German, Theoretische Elektrotechnik, theoretical electrical engineering. It consisted of the fundamentals, but not going into details with actual rotating machinery and transformers. I got my final degree in that.

Nebeker:

I see.

Pedersen:

But one year late. I got my degree in 1948. I should have finished in 1947, but because of the war I ran into problems with money. So I had to earn my living. And also the last year of the occupation there was no tuition at the university. It was closed.

Nebeker:

Oh, is that right?

Pedersen:

It closed after the Danish police was arrested in 1944. We heard also that the university in Oslo was raided and lots of students were sent to concentration camps. So the then Rector of this university advised us to stay away. And that, in a way, helped me, because then I concentrated on theoretical physics and studied the theoretical background for electrical engineering very hard.

Nebeker:

On your own?

Pedersen:

On my own, yes. I earned my living by giving private tuition to students of medicine. In those days, students of medicine had to spend one year studying before they could study medicine. They had to take one year of physics and chemistry. And physics was to many of them a very difficult subject so I got contact with students who had problems and earned my living by helping them. It was also a help to me because in that way I became very well acquainted with classical physics.

Nebeker:

Were you still in the Copenhagen area in 1944?

Pedersen:

Yes. Then in 1945 the university started up again, but because of my finances, I couldn't finish and stayed outside because I had to spend a lot of time getting bread and butter.

Nebeker:

Yes.

Pedersen:

A year before I graduated I became a full-time staff member in the — there was in those days a department for what in Danish was called Almen Elektroteknik (Theoretical Electrical Engineering) — I became a staff member there. The professor liked me very much. It meant I could stop having to deal with medical students and could concentrate on my job.

Origins of the Field of Gas Discharges

Nebeker:

I see. That was a research position?

Pedersen:

Mainly teaching. I was teaching every day, from one to five, including Saturdays. So I was one year late getting my degree. But during that period I became very interested in gas discharges, the passing of electricity through gases.

Nebeker:

That was Professor Jørgensen?

Pedersen:

Professor M.O. Jørgensen, yes. He was a pioneer in this field, and I took up his ideas and the then-Rector of this university, Professor Anker Engelund, helped me. He said to me, "You have to get out of here now, if you want to get anywhere." So he sent me on a tour to Holland and England studying high voltage laboratories. That was in 1949. During that tour I visited the University of Liverpool, where I met Professor Meek, who was one of the big names in gas discharges in those days. He was a professor of electrical engineering there, so I visited him and he said, "Well, why don't you come and work with me for a couple of years?" He arranged it so that I got a scholarship. So I could spend two years there. The condition was that I should be on my own. I had married so I had to leave my wife here, but after a few months Anker Engelund, the Rector of the university, he thought, "This is stupid. He should have his wife with him." So he arranged money so that she could join me, so she was with me then. We had a wonderful time at the university in Liverpool.

Nebeker:

He was also in the field of gas discharge?

Pedersen:

Gas discharges, yes. He was with Professor Loeb at the University of California at Berkeley. I don't remember. He was also one of the pioneers in this field.

Nebeker:

I see.

Pedersen:

So it was the right place to go for me.

Nebeker:

Could I ask you about that field for a minute?

Pedersen:

Yes.

Nebeker:

Was that a more theoretical field? Trying to understand these phenomena? How closely was it tied to practical problems?

Pedersen:

Very much tied up with practical engineering and design of high voltage equipment. Design of switchgear, design of transformers, design of overhead transmission lines. The demand for electric power was increasing. If you want to transfer electric power from one place to another, there is a limit to the distance and to the amount of power, which is linked with the supply voltage. So, before the war there was hardly anything higher than about 150kV. Here in Denmark the highest was 30kV, or 50kV. But after the war there was a boom in this. The pioneering company was the Swedish ASEA Company. They were the first to develop and introduce equipment for 400kV power transmission. One big problem in connection with this was electric sparks. So that problem had to be solved.

Nebeker:

Right.

Pedersen:

It had been studied, one of the oldest subjects in experimental physics, starting with Franklin and the lightning rod. But until the 1930s very little was known about this actual spark as you encounter it in power engineering. Small sparks in the laboratory could be accounted for by what was called the Townsend theory, which you can still find in the elementary textbooks, but the electric spark, a long and noisy phenomenon, was an enigma.

Nebeker:

There was this tradition in the last century of the study of discharges in vacuum and in gas tubes.

Pedersen:

That was kept alive. It started of course in England, with J. J. Thomson, and Rutherford was also involved in it.

Nebeker:

But I don't think of that as being connected to power engineering in any way.

Pedersen:

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It is in a way, because if you consider Rutherford's era at the Cavendish Laboratory. He died too young, he was only in his sixties in I think 1936 or 1937 when he passed away after a very, one would think, primitive operation which went wrong. But it is very interesting that one source for the input of money to the famous Cavendish Laboratory was the Metropolitan Vickers Company, in Manchester, one of the largest electrical companies. They sent staff members to Rutherford, and they helped with the construction of equipment. The association between the Russian Kapitza and Rutherford had probably not been possible without this support of Metropolitan Vickers. They were really interested. Kapitza was studying large magnetic fields. And how did you generate a magnetic field in those days? Well, you got an enormous current in a coil. The only feasible way to do it in his time was to short-circuit a large synchronous generator. So, such a thing was designed for him at Metropolitan Vickers. Transferred to Cavendish, and he studied using it and everything went wrong. The windings blew up, and of course that was a pity for Kapitza, but Metropolitan Vickers they became very _____ because here was a problem of interest to their business. So there was a very fruitful cooperation.

Nebeker:

I see.

Pedersen:

It has always been, between physics gas discharge physics, atomic physics, and power engineering. This has continued up to this very day.

Nebeker:

Yes.

Pedersen:

Meek studied at Liverpool University but then went to Metropolitan Vickers. He was not sent to the Cavendish, but because of the war he ended up in the U.S.A., with Loeb in California.

Nebeker:

I see.

Pedersen:

So did his associate, Professor Craggs. He also came to America. They were not involved in the atomic work over there, but more in radar, because spark discharges can — or have been — used also to develop radar. You have to have pulsed power, and before the invention of the modern klystron the only means of pulsing , if you had a large energy stored in a condenser bank, was to use a spark. So they developed a trigger spark gap which could be used in connection with magnetrons.

Nebeker:

You get pulses of the microwaves.

Pedersen:

Yes. So that was Meek’s work during the war. He then ended up with Loeb in California. And after the war he returned. They wrote a book which was published in 1941, I think: Loeb and Meek, The Mechanism of the Electric Spark. This was the first real monograph you could get hold of on sparks. The emphasis was on this noisy phenomenon called the spark. At the same time, similar work was going on in Germany by a man by the name of H. Raether. He was a physicist. Meek was an electrical engineer. Raether was a physicist, but he was also interested in this strange phenomenon. So he developed a theory which was later known as the Meek-Raether streamer theory for electrical breakdown of gases. There were many empty spaces in that and I have spent a lot of time on it, and have been very fortunate to be able to contribute to what is probably not the final solution to the problem, but something which makes it workable for industry.

Nebeker:

So looking at the big picture, you earlier on had the Townsend theory for very small sparks and then the Meek-Raether theory for...

Pedersen:

For long sparks. Yes.

Discharge Research by Industry

Nebeker:

Has there been any connection with lightning studies?

Pedersen:

Oh, yes. Metropolitan Vickers was of course interested in lightning because what caused the problems in power transmissions was that the power lines were hit by lightning storms, and that gave high over-voltages, which destroyed the equipment. They even found a method to utilize the electric spark to protect high voltage equipment. That was used right up to the middle of the 1950s, especially in English-speaking countries in order to protect, say, a power transformer for an incoming surge voltage. If it was, say, a 400kV transformer, the surge could be approaching two million volts. To protect the transformer you put in a spark gap before it, a spark gap from the terminal to earth, and when it was hit, because the spark was building up very, very rapidly, you bypassed it.

Nebeker:

I see.

Pedersen:

So it has been directly applied.

Nebeker:

Some of the discharge phenomena that Vickers and other companies were worried about are caused by lightning but they're also just from the high voltage in these switches.

Pedersen:

Yes, switching phenomena using high voltage circuit breakers. A lot of work was also going on in this field in the U.S.A. at General Electric and Westinghouse. The High Voltage Lab in Pittsfield of General Electric was in those days very famous. Well, of course, within General Electric it all started with Steinmetz, who was the first to build a so-called surge voltage generator where you could simulate the effect of a lightning stroke.

Nebeker:

I see. Is there a tradition for engineers in industry to publish their results?

Pedersen:

Yes. Most of the latest work in this field you can find in the Proceedings or Transactions of what was called the American Institute of Electrical Engineers. That was before the IEEE.

Nebeker:

Right.

Pedersen:

Many, many valuable publications there, from all sorts within General Electric. Also from Westinghouse names like Bellaschi, and of course a very big name in Westinghouse was Slepian, who also was interested in the breakdown of gases. He gave a course on the breakdown of gases at Westinghouse in the 1930s. It was never published, but only as an internal publication from Westinghouse. Strangely enough, the day before yesterday I got hold of a copy of it. I knew of its existence, but I had never seen it. It is on the shelf behind you. It is the second from the top.

Nebeker:

This one here?

Pedersen:

Yes. It — it's from the famous Slepian, and comes from Westinghouse.

Nebeker:

Let's see. So this was something produced, I see, by the Westinghouse Education Department.

Pedersen:

Yes. They invited power engineers from the utilities to come to these because of the fantastic importance of the subject of breakdown in gases for power engineering. There was really an industrial backup.

Nebeker:

Yes. I was just wondering if this was a field where companies like ASEA and Metro Vick; they might want to hold on to the knowledge that they had developed?

Pedersen:

No. They were very open. When I started studying this during the war there was no problems finding [information]. The only problem I had in those days was of course that all the inflow of English-speaking literature stopped with the occupation in 1940. But at the library here they had a good stock of pre-war literature. There were also a lot of famous publications in German.

Nebeker:

Yes.

Pedersen:

There were of course, in German industry, Siemens, A.E.G., were also working on these lines. Names like Rudenberg, who became a professor at Harvard when he was forced to leave Germany. Eric Gross, who became a professor at Rensselaer when he was forced to leave. There are von Engel and Steenbeck, who were at Siemens in their research laboratories on the breakdown of gases. They published a famous monograph on it in 1932 and 1934, a two-volume book on the breakdown of gases. Then von Engel had to leave because he was Jewish. He ended up at Oxford University in England.

Nebeker:

So I imagine there was a closer connection between the German engineering community and the Danish engineering community before the war?

Pedersen:

Yes, because German was the main foreign language.

Nebeker:

Main scientific language, certainly.

Pedersen:

Yes, in the pre-war years. So virtually all textbooks on the theoretical aspects of electrical engineering were in German in those days.

Nebeker:

I see.

Pedersen:

There were very little in English. Whitehead — not S. Whitehead, but J. B. Whitehead. There is an event every year at the IEEE in the Dielectrics and Electrical Insulation Society called the Whitehead Memorial Lecture. I have given that on one occasion. Whitehead published a book in 1939 in which he tried to put more emphasis on the Maxwellian background because already before the war there was a tendency to neglect the finer aspects of electromagnetism in electrical engineering. It was generally believed that all you needed to know was circuit theory. Circuit analysis. So that replaced a proper background understanding of the Maxwellian Field Theory. This, in my opinion, hampers electrical engineering education and research even today.

English Electric Company Impulse Generator

Nebeker:

Maybe we should return to your story.

Pedersen:

Yes.

Nebeker:

You had in 1951 this opportunity to work at the University of Liverpool.

Pedersen:

Yes, to 1953. I stayed there for two years. Then I returned here. The idea was that I should start planning a high voltage lab, but nothing happened. I was buried in teaching, so the holder of the chair of rotating machinery, Professor Hyldgaard-Jensen, advised me to leave. He said, "You'll bury yourself here." He tried to get me a job with General Electric in the U.S.A. He had connections with General Electric, but this was the McCarthy period, so I couldn't get a visa. At the same time as I was applying for a visa for the U.S.A., I had been offered a job at Schenectady working on gas discharges. At the same time I looked for openings in the U.K., and the English Electric Company, in Stafford, offered me a very attractive job, so in 1956 I went to Stafford.

Nebeker:

Are they a manufacturer of electrical equipment?

Pedersen:

Yes. It was in those days the largest manufacturer of power equipment in England. It was very different from most other British companies, because they went for the export market. I spent two years there, was responsible for the high voltage testing of high power, high voltage transformers. Virtually all of it went to the U.S.A. So on my visits to the States I very often have been able to touch a transformer, and I knew that some year, many years ago, I did a test on this transformer.

Nebeker:

Is that right?

Pedersen:

For example, at Bonneville, and at TVA, in Tennessee.

Nebeker:

I see. So that company must have been at the forefront of technology for exporting?

Pedersen:

Yes, and they were very research minded, so I got a very interesting job there. The need for higher voltages was increasing, and there was already talk about going from four hundred to eight hundred kV. To do that English Electric Company needed a very big impulse generator, so that they could be on the forefront. I was given more or less a free hand to design such a generator, and I was told that it should be the largest in the world. Money was not that important, I was told. I designed a generator which would give four point eight million volts, with an energy of three hundred and fifty kilo joules, which in those days was a world record. Also, another aspect of it was the way it was constructed. These are the so-called Marx generators, where you charged up some capacitors in parallel and discharged them in series.

Nebeker:

Yes.

Pedersen:

The voltage per stage was normally never higher than two hundred. Metropolitan Vickers were the experts in those days, and they had settled for two hundred. But in order to keep the induction on the generator down I asked permission to go for four hundred kV, and it was successful. Six months ago I was giving a talk at Canterbury, in England, at a conference there, I met a man from Stafford, and I asked him, "Is my old generator still there?" And he said, "Yes, and it is still being used."

Nebeker:

Is that right? The one you designed in the mid-1950s!

Pedersen:

Yes. It was so big that a nickname was attached to it within the company. It was called the Big Bertha. But it is still being used. English Electric — that name has disappeared from the scene, but the company is still there.

Nebeker:

What is it now?

Pedersen:

Well, what happened was that the British General Electric Company (GEC), which was nothing to do with the American GE, bought up first all the shares in Associated Electrical Industries (AEI), and then in English Electric (EE). It was all merged into a big company. Now this company itself has merged with a French company, Alsthom to form GEC-Alsthom. But the Stafford works is still there, and it is still the center within the company for high-voltage transformers.

Nebeker:

These high voltage generators were used mainly for testing of equipment?

Pedersen:

Yes. Well, the G.E. that was in Pittsfield managed to produce ten megavolts, but not ten megavolts to earth. It was plus five megavolts and minus five. They had two nominal five megavolts which they could then discharge at the same time. That was made mainly because GE was very active in finding out how a lightning strike develops.

Nebeker:

I see.

Pedersen:

They did a lot of work. They even installed equipment on the top of the Empire State Building and recorded all the lightning strikes which hit it. They had cameras set up on other tall buildings around Manhattan photographing everything.

Nebeker:

I see. That was to understand lightning so that they could better design transmission lines?

Pedersen:

High voltage transmission equipment, yes. And I think the main contribution to power engineering, high voltage engineering, in those years, that to learn how to live with the lightning strokes, how to protect the equipment.

Nebeker:

Yes.

Pedersen:

That was where the link was between gas discharges and industry.

Nebeker:

But it was also, as you have said, the move to higher and higher transmission voltages.

ASEA and Use of Epoxy for Insulation

Pedersen:

Yes. When I was at English Electric I witnessed the first step in another direction which has been very important for the development of high voltage power engineering. That was the introduction of epoxy as an insulating material. Normally for very high voltages you could only use oil-impregnated paper, which was messy but a very good dielectric. But if you could use epoxy you could reduce the size, for example, of high-voltage measuring transformers, which were needed to monitor the voltage on the line. You could make them much smaller and cheaper. The first attempt in that direction I witnessed at English Electric, but I was not directly involved in the application of epoxy there. I was only working in fields where it was the breakdown through air that was the major importance.

Nebeker:

I see. So you were in the research department at English Electric?

Pedersen:

I was at what was called the Nelson Engineering Laboratories, where I had a job as a senior research and development engineer, very interesting job. I think I made one of the mistakes in my life when I left English Electric. I was offered very good conditions to stay, but the ASEA Company, in Sweden, offered me a job in Västerås in their research department, working on high voltage problems. But whereas at English Electric I had worked on problems that were related to transformers and switchgear, at ASEA it would be rotating machines, rotating high-voltage machines. That meant it was all attractive to me, and I accepted. I was also put in charge of the construction of a special research lab in Västerås for high voltage, and work in connection with insulation research.

Nebeker:

Why was it that you were attracted to rotating machinery?

Pedersen:

Because I had noticed that high-voltage experts, when I met them at meetings, you could split them up in two groups and there was no communication between them.

Nebeker:

And these two groups were what?

Pedersen:

High-voltage engineers working on transformers and switchgear and the others working on rotating machines. I always found that very strange. I thought it's the same problem, basically, so at ASEA I learnt the other side of the trade, and this has been very useful for me. There I became involved in the application of epoxy to insulation of generator windings, and that made it possible to make very large — in those days ASEA was mainly known for high-voltage hydroelectric generators. When I was there we built one for four hundred and fifty megawatts, which was a very big unit for hydroelectric power stations. Also in turbo generators they were very active, and the introduction of epoxy completely changed everything there.

Nebeker:

I see, so you needed a new design for all of these generators.

Pedersen:

Yes.

Nebeker:

You were part of the teams designing these?

Pedersen:

Not designing, but doing the basic research.

Nebeker:

I see. Then design engineers would take over?

Pedersen:

Yes. But my wife didn't like living in Sweden. We came from the U.K. where there was a very free lifestyle — and Sweden in those days was very formal. Not within the company, but life in general was very formal.

Nebeker:

How large was Västerås in those days?

Pedersen:

ASEA employed about ten thousand, and the total [population] at Västerås was about seventy thousand. The climate was very cold in the winter, but very beautiful in the summer. It was about one hundred and twenty kilometers from Stockholm, which made it too difficult in those days to go to Stockholm to have a nice time.

Nebeker:

Yes.

Move to Technical University, Copenhagen

Pedersen:

Then this university offered me a job here. Not in the electric power engineering, where I should have been, but in physics. They knew that I was very much interested in the application of physics to power engineering, so I was given a job here in 1961, and was asked to set up a research group in this field. That is what I did. The response here in Denmark was marginal, but the response abroad was very good, especially in North America and Canada, but also in Sweden. All the years since I left ASEA, in 1960 — at the end of 1960, I kept a close connection with ASEA as a consultant.

Nebeker:

I see.

Pedersen:

That, again, brought me in the front line of development.

Nebeker:

How long did you continue to consult for ASEA?

Pedersen:

Until ASEA was merged with Brown Boveri.

Nebeker:

That was a few years ago?

Pedersen:

Yes. I think five years ago. I can't remember the exact date.

Nebeker:

So a very long time.

Pedersen:

What happened now was the introduction of sulphur hexafluoride, SF₆, as an insulating material for high voltage equipment.

High Voltage Research at Universities

Nebeker:

Before we start on that topic, which is very interesting, I wonder if I could ask about — because of this work you had done at the University of Liverpool, and the American you mentioned who was also at the university — whether important research in this field is going on at universities as well as in companies?

Pedersen:

As well as in companies. There was a very close co-operation. Everybody was very open. Metropolitan Vickers and the University of Liverpool, and before the war Metropolitan Vickers, and Rutherford. There is an interesting article in a book on research entitled "Research in the Cavendish Laboratories between the Two Wars." I have forgotten the name of the editor. I think it is Hendry. It is a collection of papers, and one of them tells the story of the connection between the Cavendish Laboratory and Metropolitan Vickers.

Nebeker:

I see.

Pedersen:

By one of the pioneers in high voltage engineering, Doctor Allibone, who was the liaison officer between Metropolitan Vickers and Cavendish in the 1930s.

Nebeker:

I see.

Pedersen:

He was employed by Metropolitan Vickers, and after he left Cavendish he became head of research at Metropolitan Vickers. He is still alive, still going strong, still publishing papers. He was born in 1902.

Nebeker:

My goodness. I should talk to him.

Pedersen:

He lives outside London, in Windsor.

Nebeker:

So the university laboratories were able to afford the kind of equipment needed for this research?

Pedersen:

Yes. It wasn't that expensive building an impulse generator. If you bought it from a company, it cost a fortune, but if you built it yourself, it was very reasonable. Very often the companies supplied the equipment —

Nebeker:

In order to get the research done.

Pedersen:

Yes. For example, all the equipment we had at Liverpool University came from Metropolitan Vickers.

Nebeker:

I see. Was there any tendency for the academic researchers to move in a direction different from what the companies were interested in?

Pedersen:

No.

Nebeker:

It was always a close connection?

Pedersen:

Yes, very close.

Use of Sulphur Hexafluoride for Insulation

Nebeker:

You started to tell me about the arrival of sulphur hexaflouride.

Pedersen:

Yes.

Nebeker:

Was that the first gas that was used in these switching systems?

Pedersen:

Well, until SF₆ came in, on the market, it was — SF₆ is a gas which you cannot find in nature. It is a man-made gas. Air was the insulating material, in combination with oil. For example, in switchgears you could have an oil circuit breaker, but the external system was air insulated. Always. But then came SF₆. There were two reasons why it was introduced. Somebody found out that it had very favorable properties for use in the high voltage switch circuit breaker. It is a big problem because with the very high current it was introduced as the medium for switching, replacing compressed air or oil.

Nebeker:

Oh, compressed air was used?

Pedersen:

Yes. Compressed air was used inside breakers, and sulphur hexaflouride was ideal for switching, for circuit breaking.

Nebeker:

Why was the gas originally developed?

Pedersen:

By an accident, by a French chemist, in the beginning of this century. But it was frightfully expensive until after the war. The reason why it became cheap, or relatively cheap, requires explanation. The technology how to produce it is by combining sulphur and fluoride to form the molecule. Some of the techniques used in connection with the design of nuclear reactors meant that somebody became interested in uranium hexaflouride. I remember when I worked at Liverpool we were working on the dielectric properties of uranium hexaflouride.

Nebeker:

Was that of interest to the people designing nuclear reactors?

Pedersen:

Yes. It was used in the processes related to the production of the fuel for nuclear reactors. And it is still used heavily because it is an easy gas to handle.

Nebeker:

So it is part of the separation process?

Pedersen:

Mainly.

Nebeker:

Enrichment process?

Pedersen:

Yes, yes. If you have large equipment which can produce uranium hexaflouride, you can also make sulphur hexaflouride.

Nebeker:

I see.

SF₆ and Scale of Switching Stations

Pedersen:

So it became used in large quantities. This started up already in the end of the 1950s, but in the beginning of the 1960s it was introduced in circuit breakers. It was introduced in switching stations. Normally a switching station in high-voltage systems is very large because air is the insulating medium. So if you take a typical switching field for a normal power system it would be the size of a football field. But if you build it to a system where air is replaced by sulphur hexaflouride it becomes very small. I have some photographs up on the wall up there. The top photograph is from a nuclear power station in Sweden, one thousand megawatts. This is just a small building.

Nebeker:

Yes.

Pedersen:

You can see from the catwalk the dimension of it. And that is the total switching equipment required by a thousand megawatt nuclear reactor. It would have taken an enormous space if it had been air insulated.

Nebeker:

I see. And those large pipes we see are containing compressed SF₆.

Pedersen:

They are replacing overhead lines. They are coaxial systems where you have the high-voltage conductors. The large cylinders at the bottom, they are circuit breakers. The other building below is also an SF₆ insulated station — switching station, and also in a Swedish utility system. The top one is for four hundred kV, and this one is for, as far as I remember, three hundred kV.

Nebeker:

I see. So it was a reduction in size by what factor?

Pedersen:

Twenty.

Nebeker:

In linear dimensions?

Pedersen:

Yes. A fantastic development.

Nebeker:

Yes.

Measurement & Peculiarities of SF₆

Pedersen:

At that time George Crichton, who you will meet, came to work with me.

Nebeker:

What year was this?

Pedersen:

He came here in 1967. In 1966 I had given a paper at an IEEE meeting in New York on how to calculate corona offset voltages in air. And Dr. Dakin from Westinghouse invited me to visit him at Westinghouse, so I went down to Westinghouse after the conference. At lunch he said to me that he was very interested in what I had been doing on SF₆, and then he said with a smile, "Why do you waste — " He didn't really mean it when he said, "Waste your time on air? Why don't you have a go at more exotic gases like SF₆?" That triggered me off. So I became interested in SF₆. He gave me some papers. Then Dr. Crichton came here with another man from Strathclyde, Hugh Boyd, and they were interested in measuring ionization coefficients for SF₆. So, we set up a system here to measure this, and we became very good at it. Because — because of our background knowledge in field theory, we could find out where they were doing mistakes in other laboratories. So we could make lots more precise measurements. For example, ionization coefficients in SF₆ could in those days only be measured at very low pressures, a few torr.

Nebeker:

What was the reason for interest in ionization coefficients?

Pedersen:

To make it possible to calculate the breakdown in SF₆.

Nebeker:

I see, for these power applications?

Pedersen:

Yes. And the normal pressure used in power applications was about four atmospheres. Four bars total, four or five bars total, sometimes. But all data on —

Nebeker:

Ionization?

Pedersen:

— was referring to pressures a few percent of a bar. And we managed to step that up so that we could measure accurately at half of atmospheric pressure.

Nebeker:

There is not an easily predicted correlation or relationship between the pressure of the gas and its ionization coefficient?

Pedersen:

There is. But SF₆ is a peculiar gas. It is very heavy. The molecule is large. So it is at the borderline between a gas and a liquid. For example, if I fill this mug with SF₆ from a bottle, the gas, so that this is filled with SF₆, and I have another empty here, I can just take it and put it from one to the other. And it will stay. Although there is no lid, it will stay in there for a very long time because —

Nebeker:

It is so much denser.

Pedersen:

Yes. It is very near the critical pressure — temperature. So it is difficult to forecast.

Nebeker:

I see.

Pedersen:

It can be done if you know the compressibility of SF₆, that is the deviation from the normal volume-pressure gas law. Normally you have volume times pressure is proportional to temperature. But with SF₆ this is not so. So you can introduce a correction factor called the compressibility factor. We had also managed to measure that. So we became very active in this field.

Nebeker:

I see.

Pedersen:

In 1972 ASEA decided to start up, very late. Their competitors were already selling it on the market. But this late start meant that ASEA was not making all the mistakes of the competitors. So I had a very wonderful time for them as the consultant, helping them in the design.

Nebeker:

I see.

Pedersen:

The first step was to decide on a voltage for prototypes. Most of the market in those days would be four hundred kV, but it is very difficult to scale up in voltage, so we decided to develop all the basic modules for eight hundred kV. Then it is easy to scale down. So, we designed all the prototypes, and ASEA became quite good in this field. They realized that they were late, so they went for a share in the world market of about five percent. They were very good, were very successful, and I had a very nice time helping them.

Nebeker:

Were you giving much of your time to your consulting work at that period?

SF₆ and Surface Roughness

Pedersen:

Yes. And here we had found out that you had to be very careful believing physical data. For example, if you asked a physicist about breakdown in SF₆, he would say that if you have a pressure of one bar and you have a distance of one millimeter, it will break down at about nine kV. But experimentally it was known that these theoretical values could never be attained. The fact is, you always ended up with something half that value.

Nebeker:

Why is that?

Pedersen:

It was a puzzle for many years. But at the same time as we were working on this, they were working on it at the Technical University in Dresden in the then D.D.R. Two names there: Hauschild and Mosch. They were very active, and they had also experimentally found out that you could never achieve the theoretical limit; you always ended up with fifty percent of it.

Nebeker:

I see.

Pedersen:

So what is the reason? They started looking for it experimentally. They guessed that it must have something to do with the texture of the surface. So they introduced a concept of surface roughness in relation to breakdown studies in SF₆. They did a lot of experiments. We supplied all of the theory. So it was a wonderful cooperation.

Nebeker:

I see. Surface roughness was not something that had been studied before these systems?

Pedersen:

No. You see, if you have an air system, if you design a circuit breaker for compressed air, normal finishing processes is good enough. You can consider these surfaces to be ideal.

Nebeker:

I see.

Pedersen:

Also, when you work out the field. But, in SF₆ you have to take the microstructure into account. Not the atomic microstructure, but the macroscopic roughness.

Nebeker:

I see.

Pedersen:

We managed to develop a criterion by which we could introduce what is called a figure of merit for these gases. All these gases, SF₆ and other gases which have been considered, are heavily electro-negative. So they are electron-attaching gases. We introduced a concept which we called a figure of merit, which we could measure if we were given a gas. Knowing a figure of merit we could tell the influence of surface roughness.

Nebeker:

I see.

Pedersen:

Audio File

MP3 Audio
(230 - pedersen - clip 2.mp3)

This is used in design all over the world today. The first company to really accept what we were doing here, and what they were doing in Dresden was Mitsubishi and Toshiba and — what's the other big company in Japan? [Hitachi?] My memory is not very good for names. Three big Japanese companies who were all in the SF₆ business. They became very interested. I came to know them, their research people very well, especially Dr. Tohei Nitta, who was head of all SF₆ work in Mitsubishi. Dr. Nitta is today living in Boston, in the U.S.A., where he is head of a research lab which Mitsubishi has set up there. It's more in the line of computer applications now. But he was one of the pioneers in the practical aspects of it. Another problem when they started using these things was that although your main insulating material is SF₆, you must have solids to keep the — the parts apart. For example, in these bus power systems, where the conductor is a tube in another larger tube, it is a coaxial system, so you must have spacers to keep the inner tube in position.

Nebeker:

Right.

Pedersen:

Charge accumulation on such spacers became very important. Then came the problem of how to forecast these charge distributions. I think that is one of the greatest contributions we did make to this field. We have found out how we can calculate these things in a simple way. You can always use a sledge hammer approach and try to solve the Poisson differential equations for the total system, but in engineering money is an important parameter, so if you can invent a method where you can bypass all these costly computational procedures, you are well off. That changed our line of research from the actual breakdown more into the interface between a gas and a dielectric. We developed methods by which you could work out, from probe measurements, how charges are distributed. Then the next step concerned these dielectric systems you must have in your system — they are never ideal. If it is, for example, an epoxy spacer in an SF₆ system, there will be small voids, small cavities in the epoxy. You cannot get rid of these. They are there and you have to live with them.

Nebeker:

So you have to account for that in theories.

Pedersen:

Yes. And since they will be filled with gas, either air or SF₆, or things that can be introduced during the manufacture, you get electrical discharges in these voids. They are called partial discharges. If you have a large system and have a small void, you don't even know where the void is, but you can detect at the electrodes on your system that something is happening. So the problem is from a detectable system to work out what is happening in the void. That is what has occupied me for the last five, six, seven years. Full time.

Nebeker:

The importance of that is that one can then better design these spacers —

Pedersen:

Yes.

Nebeker:

— and other uses of the dielectric.

Pedersen:

At Lake Como later this month, the subject is partial discharges in voids in solid dielectrics. Eric Forster was also working in this field. There are international standards for this, but they are all based on very old principles, based on circuit theory, so they are very misleading. But it is possible by field theory to design and develop criteria which can be used. That is what has occupied me for the last five, six, seven years. I am very happy because in my retirement I have been able to continue this work, and it is continued by Crichton and McAllister in the power engineering department.

Nebeker:

I see. And you continue to work with them?

Pedersen:

Yes. I have been given permission to keep this office, but I have no funding, so if I want to go to a conference in America I have to pay myself. There is no back up in Denmark for what we are doing. I have not tried to get other jobs as a consultant since the merger between ASEA and Brown Boveri. I am getting old, and I have a problem with my health. I suffer from prostate cancer and have to spend an afternoon in the hospital every four weeks, and it means that I cannot work as hard as I used to. But in this period — up until now I have been able to work about half time. So I spend half a day here almost every day, keep in contact with my colleagues, and keep publishing. It is very fruitful. Although our lab was closed down when I retired, the work is being continued in the power engineering department, where they have got very good working conditions.

Information Exchange Between East & West

Nebeker:

You said that earlier you had this fruitful relationship with the East German laboratory where you did the more theoretical work and they did the experimental.

Pedersen:

Yes. That involved a lot of traveling from my side to Dresden.

Nebeker:

They didn't have the money to travel here?

Pedersen:

No, neither the money nor permission. I was also helping them to be known outside D.D.R. They published everything in German, but I persuaded them to try to publish in North America, and at first there was a series of conferences organized by Oak Ridge National Laboratory, by Prof. Christophorou, who is an expert in conduction of electricity through gases, or gaseous electronics as it is called these days. He arranged a large number of conferences on gaseous electronics and breakdown phenomena, where people from universities met people from industry, exchanging point of view; very fruitful. I have been to them all. The last one (the 7th) was this year in April in Knoxville TN, USA.

Nebeker:

When did these start?

Pedersen:

The first one, I think that I attended was 1978.

Nebeker:

So the first one was in 1978.

Pedersen:

Then every other year he had a conference there. I told Christophorou about the important work they were doing in Dresden and then he invited them to submit papers. But they couldn't present it, so I did that for them.

Nebeker:

I see.

Pedersen:

When it became easier for them to travel, even before the fall of the Iron Curtain, I used my influence with Prof. Christophorou so that Dr. Hauschild, who was the main person at Dresden, was an invited lecturer at one of these conference on Knoxville. So I was also involved in there to keep — to get opportunities for traveling. I was also an external examiner for Ph.D.s in that period there.

Nebeker:

I see. Your career tells a lot about how international this field is. You've worked in several countries yourself, and you've mentioned connections with Japan and East Germany. And the exchange of information has been pretty open?

Pedersen:

Yes. Between East Germany and West Germany, when you had the Iron Curtain, they complained in Dresden that nobody in West Germany took any notice of their work, and this was absolutely true. It was silenced to death.

Nebeker:

Before you made the effort, or encouraged them to make the effort, they hadn't tried to publish in English or reach an audience outside?

Pedersen:

No. But they published a book on breakdown in SF₆ in German, and the idea was that it should come out in a new edition, and I should translate it into English and add some chapters to it. But then my health problems started, so we had to drop that. It never materialized, and today there is really no need for it.

Nebeker:

Has there been important work by the Russians in this field?

Pedersen:

Yes. They were also very active in SF₆, and they were also, through Dresden, aware of what we were doing.

Nebeker:

And there has been open communication with the Russian researchers as well?

Pedersen:

Yes. The Soviet Academy of Sciences invited me in 1980. They invited me to a conference in Minsk, in Belorussia, where I was an invited lecturer, a guest. I was invited to talk especially about SF₆ and its application in power engineering.

High Voltage Insulation in North America

Nebeker:

I see. If one wants to get kind of an overview of the last fifty years of this field, from what you have said it is clear that Sweden and Germany, and England, and I assume the United States have been in the forefront.

Pedersen:

In the United States it was especially Westinghouse. The utilities in Canada played an important role, especially Ontario Hydro. We have had here close connections with Ontario Hydro. In an EPRI-sponsored project in which Ontario Hydro Research, they were organizing everything. It was about spacers in SF₆ systems. The participants were the University of Connecticut, Westinghouse, and of course Ontario Hydro, and ASEA, and Brown Boveri — this was before the merger, so both ASEA and Brown Boveri were involved — and Siemens. It was also a very broad international cooperation in which you had universities co-operating with utilities and with industry.

Nebeker:

Have utilities in all the advanced countries followed pretty much along, so in Italy, and France, and Spain, and so on?

Pedersen:

Yes.

Nebeker:

They are moving into the SF₆ systems?

Pedersen:

SF₆ is a big market today, a really big market. Not so much in North America, because in North America a strange thing has happened. I don't know quite what is the background before it, but SF₆ has not been so successful in North America as elsewhere. If I have to guess what is the reason, I think it could be a very good example of how careful you have to be when you have a cooperation between academics and industry, so there is no misunderstanding. People with a mainly academic background should be aware of the fact that it isn't that easy to design an SF₆ insulating system. If I consider what has happened of accidents with these things in breakdowns, mainly in Canada, I cannot help get the feeling that because of pressure from the utilities, from the academic staff and their research departments, that the manufacturers have been too optimistic in design.

Nebeker:

Then there were subsequent problems with the equipment?

Relation of Academic to Industrial Research

Pedersen:

Yes. The same thing happened with equipment delivered by Brown Boveri. They also leaned very heavily to academics. There is an amusing story which I think I can tell safely today. I visited Brown Boveri many years ago, and in their high voltage lab, there was a Dr. Gänger, one of the pioneers of gas breakdown.

Nebeker:

Could I ask roughly when this was?

Pedersen:

This must have been in the early 1960s. And we were talking about SF₆ and he said, "Come up to the roof of the high voltage lab." We went up there, and he had a prototype system running there, busbar power systems with SF₆ — to get experience. He knew that the following day I would be visiting Brown Boveri Research in Baden. This was also in Baden, but in the works. But he knew that I was going to see the research. So when I left he said, "Please don't mention anything to the research staff because then they will interfere and destroy everything!" Dr. Gänger was a person with the same background as me. He knew the physics of it. He was the author of one of the best — well, the only real standard work in German on breakdown in gases. But he also kept closely in touch with industry, so he knew the industrial problems, just as I have always been fully aware of the industrial problems. But those working in research departments in industry were often not aware of these things.

Nebeker:

And they would want to move in a different direction.

Pedersen:

Yes, they would. They would say, "Why are you wasting your time getting long time experience with SF₆ because we can tell you the breakdown field strength is nine kV per millimeter bar?" But Dr. Gänger knew that life wasn't that easy.

Nebeker:

I see.

Pedersen:

Of course the research department learned when they got really in touch with the phenomena that you have to be careful. So it just shows that there are these two input ways to the field of gas breakdown.

Nebeker:

Yes.

Pedersen:

When I gave the Whitehead Memorial Lecture — I have forgotten when that was. I retired in 1991, so probably 1989. It was the year when the Iron Curtain fell — the wall in Berlin was broken down. It was that year, because it was in that week that the Whitehead Memorial lecture took place in Leesburg, near Washington. I knew that in the audience you had physicists and engineers, so I tried to indicate where the problems were that if you see it from the side of engineering. It is not the same view as from the other side. I think there were problems on communications. The physicists were more interested in fundamental things like cross-sections and molecular problems, whereas the engineer is interested in the macroscopic aspects of it. In air the gap is so narrow between the two points of view, but in electro-negative gases you have to be aware of the fact that they are entirely different.

Nebeker:

So that is an interesting example as the technology advanced, it was more of a split between the physics oriented and the practical.

Pedersen:

Yes. It always occurred to me when Dr. Gänger said to me, "Don't tell them," at the research lab that he was afraid that they would use their background knowledge in physics —

Nebeker:

To tell him that he should be doing something different.

Pedersen:

Yes.

Connection with AIEE & IEEE

Nebeker:

Could I ask you about your connection with IEEE, or maybe with the AIEE before IEEE was formed?

Pedersen:

When I was at English Electric I worked on a special problem related to high-voltage transformers, namely the distribution of surge voltages in a transformer winding. English Electric was producing special winding coils, interleaved winding, and no theory was available for that. So when I was there I got the basic idea of how to do it, and when I was at ASEA, where my job was very free, I was working as a consultant, sitting in an office and people could come and talk to me, but I could more or less decide by myself what I would do, so I completed the theory there. Of course my bosses were aware of the fact that I did this work, and we followed all the ethical rules that knowledge I had from English Electric I kept for myself. Did not tell them, ASEA, without permission. If I got permission from English Electric I would, of course. I wrote a paper which I showed to another of the old-timers in high-voltage engineering, Raul  Willheim, also one of the pioneers in Germany. He had to leave. He was with AEG, and in 1933 he had to leave. He settled down in London as a consultant. He was representing an Australian utility at a meeting in Västerås. I took him out for lunch and we were talking about transformer windings because I knew that years back he had also done work in this field. So he persuaded me to publish it. I got permission from English Electric, and I got permission from ASEA to publish it, but the problem was that having it out in England would be difficult because the policy of the Institution of Electrical Engineers in London was, "Never publish anything which could be critical to an important industrial product in England because that could destroy — "

Nebeker:

Hurt their business?

Pedersen:

Yes.

Nebeker:

Their reputation?

Pedersen:

They could say, "Well, isn't it strange that a man who is at this time employed by you can tell how this works?" So I went to see them and we decided that the best thing was to have it out in America. That was a year before the formation of the IEEE.

Nebeker:

So that was 1962?

Pedersen:

Yes. Dr. Willheim then said to me, "Have you any connections in over there?" I said, "No, I haven't." He said, "Well, this is very important you have it out there, so I will use my influence." He sent a letter to an old friend of his, namely Dr. Eric Gross, who was a professor at Rensselaer, and who was before the Hitler era one of the top research persons in the German AEG. Willheim told him about this paper, and Gross wrote to me and said, "Send the manuscript to me and I will submit it." Which he did. So it was accepted for the last big meeting in before the merger. But then they decided that the first meeting after the merger in February 1962 should be a very big event.

Nebeker:

Wasn't that 1963?

Pedersen:

1963, yes. I should have presented it at the summer meeting in 1962, but Gross then said, "We have postponed it until February 1963." That was my first visit to the U.S.A.

Nebeker:

That was at the first joint meeting of the two?

Pedersen:

Yes. Where I presented this paper.

Nebeker:

It was published in the IEEE Transactions?

Pedersen:

Yes, Transactions on Power Apparatus and Systems. Then I met certain persons there who showed an interest in my work. I managed to get money so that some years later I could go back to other meetings arranged by them. I was invited to apply for membership, and in 1966 I became a Senior Member. I then started a very happy period when I was commuting between Denmark and the U.S.A. twice a year. I attended for a large number of years, all the summer Power meetings, all the winter Power meetings. And published since then everything there.

Nebeker:

I noticed that this volume, Festschrift, was published by the Dielectrics and Electrical Insulation Society.

Pedersen:

Yes.

Nebeker:

So you were more connected with Power Engineering?

Pedersen:

In the beginning, with Power Engineering, because this society did not exist. But there was so much work in the Power group on dielectrics that this society was formed. Then my interest was transferred to that.

Nebeker:

I see.

Pedersen:

It is now there, and it has been very fruitful for me.

Nebeker:

Yes.

Pedersen:

I was very pleased when the editor of this, Dr. Van Roggen, heard about my seventieth birthday and decided to publish this.

Nebeker:

So for you it was an opportunity to present your work for that group and then you published in the Transactions.

Pedersen:

We have published many papers in the Transactions on electrical insulation throughout the years. All the major papers we have published on SF₆, and also on partial discharges. It is all in that society.

Nebeker:

Have you had any or much connection yourself with the IEEE Denmark Section?

Pedersen:

Very little. Perhaps I shouldn't say this, but when I became a Fellow of IEEE, my idea was that it was the Power Group that gave me the fellowship, and the idea was that I would go to one of their meetings and receive the diploma. But I was very ill and was in the hospital at the time, so I couldn't go. So they sent the diploma to the Denmark Section. They were not very pleased because of this problem with my namesake. So instead of handing it over to me at one of their meetings, they saw my secretary and found out which day I was in, and which day I was not in, because my health was such that I was only in one or two days a week. So it was officially handed over to my secretary. I have heard nothing from the Denmark Section about my fellowship. I have heard nothing from the Denmark Section about this. It has been silenced to death here in Denmark.

Differences in Today's Engineers

Pedersen

One thing which I have noticed in the past decade or so is the decline of knowledge about the theoretical, physical background for insulation research. For example, if I attend conferences in America, there would be many interesting papers on breakdown in solids, but they all attack the problem from a molecular point of view. They talk about charge being ejected, and Fermi levels, and all these things. They seem to have forgotten that if you have a piece of dielectric of such a size that it is used in power engineering; it is macroscopic. According to one of the fundamental principles of quantum physics, the correspondence principle, they should know that when you have a large system you shouldn't attack it from a molecular way, but should use macroscopic physics because if you could do it in a molecular way, if you knew all the boundary conditions, you would end up with precisely the result of macroscopic physics.

Nebeker:

Right.

Pedersen:

But they don't do it. So a problem like charge accumulation in the dielectric is very important because of the interest in high-voltage D.C. for long-distance transmission. In a D.C. cable there will be a temperature gradient, and that means that you have a variation in conductivity, which leads to charge accumulation. But they're not aware of that. They think if there are charges, they must be injected from the outside. This is because they don't know classical physics. They have probably never heard about this book. [Holds up a book]

Nebeker:

Ernst Weber's Electromagnetic Theory.

Pedersen:

Yes, and if you try to tell them that you can approach it from a classical point of view, they just laugh. I think the reason is the availability of personal computers and easy availability of programs, so that you replace a time spent reading books with looking up a catalogue, "Which program can I buy?" Then you buy a program. So we have tried at the last International Symposium on Electrical Insulation in June 1994 to show via classical physics that you can work out precisely how these charges are distributed in the dialectric. We presented a paper on charge accumulation in DC cables. My time is running out. I am seventy-three and in frail health, but I would wish that in universities where they are teaching electrical engineering, they would introduce courses in classical physics. I don't think it should be called mathematical physics, as I think Weber has once called it, but one could use the words Theoretical Electrical Engineering. There is no good textbook in English, but there are two good books in German. But this theoretical background just isn't there.

Another aspect when I was young: you could always discuss things with other workers in this field. You could use the language of mathematics. But this language could then be used because you knew that those who you were communicating with knew the language of mathematics. They considered it a language. They could read mathematics. They could probably not solve complicated problems, but if they saw an equation, they could read it and get the meaning out of it. That is not so today. Young researchers in this field are very badly off.

Nebeker:

I see. And part of this is the great use of computers in electrical engineering?

Pedersen:

Yes, I think so. It's my own personal view, of course, but it is evident when I go to conferences that the lack of fundamental knowledge, background, is there even with persons with a PhD.

Nebeker:

On the other hand the computer must have meant a lot. I noticed, I think, your first paper was on calculation of voltage breakdowns.

Pedersen:

Yes. It is a very useful tool which we cannot do without. We have used it here to our own benefit and are very happy with it. But you have to know how to use it.

Nebeker:

Yes.

Pedersen:

If we do a field calculation, we can immediately see if the result we get from the computer has meaning because we know a little bit from this book.

Nebeker:

Yes.

Pedersen:

That's it.

Nebeker:

Thank you very much.