Giovedì 23 Nov 2017


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Study Committee “Rotating Machinery”

I joined Ansaldo organization at the beginning of 1973, as a young electrical engineer.

My cooperation with Cigré started almost immediately and my technical life in Ansaldo from that time kept on running in parallel with my activity for Cigré. I retired from Ansaldo at the beginning of 2005, but I am still active in Cigré today.

Since the beginning my reference Study Committee was the SC 11 “Rotating Machinery”, named today study Committee A1, which represented the main field of activity and my major professional interest. At the beginning of the seventies the Italian National Member was Mr. Calcia from Tecnomasio Italiano Brown Boveri but Ansaldo had decided to get more and more involved in the activity of SC 11 and the following Italian National Members came from Ansaldo.

Mr Calcia was replaced by Mr. Odaglia, then it was the turn of Mr. Barozzi who terminated his mandate in 1990. From 1991 up to 2000 it was my turn and I was followed by Mr. Macciò and Mr. Tartaglione, who is still in charge. All these guys came from the Rotating Machinery Area of the Engineering Department of Ansaldo’s.

As far as Cigré is concerned, the first task I was assigned by my Direction was reading and answering some technical questionnaires. Personal computers and electronic post were not available at that time and therefore to work on technical documents was much more difficult than it is now and it was much longer to complete an inquiry. Questionnaires’ were by themselves a way to greatly improve knowledge of a young and a curious engineer like me. Questions very often used to discover unexpected problems about machinery and they were an incentive for additional investigations and new approaches to the everyday office work. In addition, to be involved in questionnaires was an excellent chance for getting in touch with people from all over the world and improving English. To be honest I had only studied French and at the Secondary School and this activity was for me the incentive for studying English too.

With the passing of time many of the contacted technicians had become dear friends, I must say.

One of the first thing I learned was that Cigré was a community of friends instead of a real arena for competitors, as I had thought at the beginning. The first stage represented by the compilation of questionnaires was followed by the technical meetings in different countries.

I joined my first Cigré meeting in 1977, in Switzerland. That meeting was held in Losanna hosted by Prof. Chatelain of the École Polytechnique Fédérale de Losanne. That was the occasion for meeting technicians from the most prestigious manufactures all over the world like General Electric, Siemens, Brown Boveri and so on. At that time manufacturers of large electrical rotating machines and relative factories, differently from today, were very numerous and spread all over the world: I mean in Great Britain, Belgium, Sweden, Norway, Japan, China, Russia, Hungary (this list is not complete and not written in order of importance), etc. Also important Utilities were present in SC 11 like EDF from France, Ontario Hydro from Canada, ESKOM from RSA, and so on. My excitation and my concern were at the utmost but my worry suddenly disappeared when I noticed that one of the maximum experts had taken off his shoes under the table and kept on attending the meeting in his socks: that was the spirit of Cigré with no formalities but simply inspired by friendship and freedom.

My first more official meeting took place in Paris in 1978, that is the following year. Technical meetings used to be taken in the Sorbonne University premises: the Palais des Congrès were yet to come at that time. Rooms were not very comfortable and the maximum technological tool was a projector for transparencies.

In the following odd years I could visit a lot of foreign countries: United States of America, Brazil, Great Britain, Norway, Sweden, Russia, South Africa, Japan,  Switzerland, Canada, Australia, China, Romania as far as I remember. All technical meetings included touristic tours and technical visits. In Brazil (1983) I had the great pleasure to meet Prof. Paris and Mr. Manzoni for the first time. It was the beginning of a pleasant cooperation. For the occasion I was replacing for the first time my boss, Mr. Barozzi, as Italian National Member and I had the chance of visiting impressive Itaipú Hydro Power Plant, on the Paraná River( 20 units for a total capacity of 14 GW today), and the pertinent AC-DC conversion plant (6300 MW at ± 600 kV). The Itaipú HVDC transmission consists of two bipolar HVDC transmission lines bringing power generated at 50 Hz (Argentina units) to the 60 Hz network running for about 800 km.

I got really surprised in 1986 when I discovered that the location of the movie Mission performed by Robert Deniro was the area of Iguaçu falls which I had visited during the Cigré meeting in Brazil. I had been there!

Another remarkable event is related to the demolition of the Iron Curtain in Berlin. I organized a meeting of the WG Large Motors and Drives in Milan and I could host Professor Yury Vinitsky from VNIIE for his first trip outside URSS (1992). We started a good friendship which still continues and involves our families too. As I said before that was and still is the spirit of Cigré.

Some years later Professor Vinitsky and the Russian Cigré Committee organized the Study Committee meeting in Moscow (1995) and I had a new surprise: the meeting took place on a boat navigating on Volga river, for safety reasons. An additional surprise was that it was not possible to pay anything by American Express as this credit card was not accepted in Russia at that time.

Another peculiar event I will never forget was the meeting in South Africa (in 1993, two years before the meeting in Moscow). During a ceremony we were received by the Major of Cape Town and were said that South Africa at that time was a laboratory for cohabitation of different human races: Apartheid and racism were still very serious and they seemed to try to break this terrible barrier.

Each country had its own peculiarity and those technical meetings were an important chance for discovering some aspects impossible to find out for simple tourists and the role of the Cigré Members of the organizing countries was essential to this aim.

Also Italy organized some important meetings in which I got personally involved, with the WG Large Motors and Drives. The different locations were. Milan, Trieste, Florence and Genoa. But the more exciting experience were the two different meetings in Florence. The first one was held in combination with the Transformer Study Committee in 1987 and the attending persons could not only visit Volterra and San Gimignano but also some impressive Enel geothermal power plants. As known Italy has always been market leader in the field of geothermal energy.

The second event was a Colloquium, the first in Europe, jointly organized by Cigré and Epri, still in Florence (1997). The idea of this joint Colloquium was launched by the same Mr Tontini, Mr J. Stein (EPRI) and some technicians from EDF in a previous meeting in the USA.These two events were organized by Ansaldo and Enel in cooperation with the Italian National Committee.

Mr. Tontini, a good friend of mine, from Enel helped me in managing these two special events in an excellent way and the two meetings obtained a great deal of success. Frankly speaking, I think that a key of the success were Italy and Tuscany because all foreign people love our country for art and the landscape.

Coming back to myself and my Cigré history, I started with topics run by the WGs Hydrogenerators (11.02) and Large Motors and Drives (11.06). There were a lot of innovative subjects mainly related to electronics. Variable frequency was one of the field of my usual work in Ansaldo and one of the most exciting subject for SC 11 Experts. Pumped Storage Power Plants were already very popular in Italy due to the quantity of important mountains in the North of the country.

I had been involved in the design of 170 MVA hydrogenerators for the pumping storage P.P: of Chiotas-Piastra in Piedmont. The generators were manufactured by Ansaldo and Tecnomasio Brown Boveri. The units of Chiotas were started via the pony-motor placed in Rovina-Piastra P.P. when passing from generation to pumping regime. An electronic variable-frequency starting had been considered as an alternative option at the design stage. Italy was a leader in the field of high hydraulic head (1048 m in case of Chiotas) and as a consequence as far as high-speed machines were concerned.

As known, in many cases, the construction plan of many pumped storage power plants was seen in combination with the development of nuclear power plants, in order to employ energy overproduction (at low cost) during night. This opportunity stopped with the Italian moratorium on nuclear production after Chernobyl accident (1986). In any case these power plants were mainly taken into consideration by Italian National Electricity Board for peak-load regimes. In case of motors, variable speed  supply is profitable in all applications where motors have to operate at different speeds.

At the beginning Adjustable Speed Drives found application in traction but rapidly were considered for application in power plants (fans, pumps, etc.) too, in order to increase efficiency and save energy. Industrial applications were covered by Cired while energy production applications were considered by Cigré, but the border between the two associations was very thin and feeble, as I could learn by experience in conferences. Generally speaking size of motors was much larger in the field of Energy than in Industry. At that time Ansaldo was market leader in ASD applications having designed, manufactured and installed (1984) one of these equipments for the balancing a overspeed testing room of rotors of large turbines and turbogenerators in its premises in Genoa-Campi. It was the matter of a synchronous turbomotor rated 3650 kW between 2160 and 4320 rpm and working at constant torque from zero to 2160 rpm ( corresponding to the world maximum difficulty coefficient for a rotating machine at that time). The turbomotor had one single stator winding and it was fed by an LCI converter cooled by oil. Surprise: the converter has been replaced by a more modern LCI air cooled converter at the beginning of the new century while the motor is always the same and it is still working perfectly!

Coming back to Cigré, the Convenor of  WG 02 Hydrogenerators was Mr. Gamleseter from Norway while the Convenor of WG 06 Large motors and drives was my dear friend and teacher Philip Conceiçao, from Kennedy and Donkin UK, something like a guru in the field of Rotating Machinery, but not only, for the reason that he was very deep in knowledge of all components of power stations and of the whole plant.

Philip abandoned his rôle in Cigré in 1992 when he got seriously ill but he continued supporting the WG activities up to the end.

Philip was replaced, as Convenor of WG Large Motors and Drives, by Mr. Alan Mitchell from Eskom (South Africa), another dear friend of mine. In 1998 it was my turn and I become the Convenor of this Working Group and I was in charge up to the end of 2014.

For me it was an incredible emotion to run a working group of Cigré interconnecting the most important experts of the world, suggesting new topics, structuring questionnaires, revising answers from different countries, and preparing the final reports, I tried to be very active even if the task was very hard and usually not compatible with everyday office work.

It used to be necessary for me to devote evenings, Saturdays and Sundays to Cigré, but this is the story of all guys really involved in Cigré activities, independently on the Study Committee and the Working Group. The first questionnaire report on ASDs was published in Electra in April 1989 and I ran more than fifteen questionnaires, five out of them on ASDs.

In 2000, when I was replaced as Italian National Member, I obtained the Committee Technical Committee Award and I am still the only Italian awarded by this special prize. I have spoken about the WG Large Motors and Drives so far but very interesting subjects from the other SC 11 Working Groups have to be underlined too. One of the interesting points, which is a transversal technique is, represented by the topic of Partial Discharges. The experts of the Study Committee Rotating Machinery started to speak about this special subjects for rotating machinery at the beginning of the eighties, as far as I remember.

I had the chance of visiting the laboratories of Greg Stone, one of the world gurus for PDs, in 1987, thanks to Cigrè. Ontario Hydro was very advanced at that time starting from the initial application on GIS. The first machines involved were hydrogenerators but motors and turbogenerators followed. Since then a long way has been gone and today PDs measurement is a diagnostics technique universally used and appreciated for investigations on rotating electrical machines. Because of the importance of stator insulation conditions we can say the PDs are the real base for diagnostics. Italian manufacturers, Universities ( i.e. Trieste, Bologna and Genoa), and ENEL got involved in development of this technique since the beginning.

I can mention Prof. Rabach and Prof. Contin from Trieste, Prof. Montanari from Bologna and Prof. Centurioni from Genoa. For ENEL, as far as rotating machines were concerned, the guys involved were still my friend Giorgio Tontini and his team in CREL (Centro Ricerca Elettrica of Enel). Another very important area of development has been the increase of unit power. At the beginning of ’70 the maximum rate of air-cooled turbogenerators was about 100 MVA while now is reaching and overcoming 450 MVA. At the same time hydrogen-cooled turbogenerators increased their capacity up to 800 MVA, in case of indirect cooling of the stator and direct cooling of the rotor and use of HTC (High Thermal Conductivity) insulating tapes or simply in case of direct cooling of the stator. In case of direct cooling of the stator winding by water and direct cooling of the rotor winding by hydrogen 4-pole turbogenerators rated more than 2000 MVA for nuclear applications have been supplied. To the development of maximum-rate machines a workshop was dedicated by Cigré in 2008 in Paris.

While in case of maximum capacity for nuclear the contribution of Italian manufacturers has been necessarily limited after the referendum in Italy, the contribution to the increase of the other classes of turbogenerators has been important. Development in industry run always in parallel with Cigré investigations.

The keys of improvement were:

         - More powerful calculation tools

         - Better management of ventilation/cooling system

         - Rotordynamics deep study

         - Better knowledge of local/concentrated stresses (mechanic, magnetic, electric and thermal)

         - New insulating systems/materials.

 The last item deserves further comments.

The last two decades of previous century were distinguished by the extension of global VPI (Vacuum Pressure Impregnation) from motors to air cooled turbogenerators. This experience involved Ansaldo too since the shift from GE license to the ABB one and lasted for about twenty years.

 More recently service indications promoted an additional shift from global VPI to single-bar VPI. After termination of license from ABB ((2005) Ansaldo came back to its own property insulation system, the “resin-rich” one. The two insulation systems are both present on the market and give a precise identification of the technology of each single manufacturer. Ansaldo could always give an important contribution to Cigré questionnaires on this topic thanks to its own long experience in both technologies.

Another item about the same topic is represented by development of high thermal conductivity (HTC) mica-tapes. They started to study this kind of tapes in Switzerland at the beginning of ’80, but the initial tape was too difficult to handle: being too brittle and fragile. At the beginning of the new century a new version of the high conductivity tape was set up for the application in VPI systems. A similar high- performance tape is now available for resin-rich insulation systems. too. We can say that the new tapes turned to be a real breakthrough for turbogenerators and a milestone in the history of rotating machines. Now has started the era of nanotechnologies also for insulating materials and the first industrial results seem very promising.

Other important topics have to be mentioned even if they do not succeed. An outstanding example is given by SC (Super Conductive) turbogenerators. All manufacturers had been working on this subject up to the end of ’90 but stopped their activities after the Chernobyl accident, when, for a long time, the request for very large unit power stopped. Siemens was the last manufacturer in Europe to stop experiments while the Japanese kept on activities up to the end of the last century. I mean Cold Superconductivity obviously (cooling by cryogenic liquid with temperature almost at the absolute zero degrees).

In more recent years application of Warm Superconductivity took place in motors, hydrogenerators and generators for wind units. Naturally we speak about ratings very different from the previous ones when the goal was represented by record rates.

The WG 05 of SC 11 devoted to Super Conductivity changed scope and moved to new technologies and wind, at the end.

Another interesting new product presented by ABB in Cigré meetings was the POWERFORMER™. It was the matter of a large size hydrogenerator with high voltage cables directly located in the stator slots, There was no necessity for a step-up transformer between the generator and the network. After a testing period on some prototypes in real scale the solution was extended to turbogenerators too. The birth (1998) and the death (2006) of the idea were stated by ABB directly during Cigré meetings. The main problems they tackled with were related to availability and protection systems. By the time other points covered were the impact on generators of interconnection to HVDC, grid codes, dispersed generation, efficiency, etc.

We can conclude that the work and the support of rotating machines manufacturers and the continuous action of survey and promotion performed by SC 11 of Cigré have an important place in the Electrotechnics history. It would be essential to continue this combined effort but some limits exist: mainly concentration of technologies and lack of young engineers interested in rotating machines unfortunately!


Genoa the 13th of May 2015                                                                    Enzo Tortello


  SCRM Stator of a 3 phase fig1 piccola SC RM Pietrafitta fig2 piccola

Reproduction by the courtesy of Fondazione Ansaldo


  SC RM Staking of stator fig4 piccolaSC RM Facility fig5 piccolaSC RM View of a complete fig6 piccolaSC RM Stator of 350 MVA fig7 piccola  SC RM Rotor with the winding fig8 piccola  SC RM Balancing and overspeed fig9 piccola  Turbogenerator fig10 piccola  SC RM Turbine rotor fig11 piccola

 Reproduction by the courtesy of Ansaldo Energia s.p.a.