ADVERTISEMENT testing, and commissioning and to do the assessment of all the measurement protocols related to hydro generators. Hydro Leader: Please tell us about your book How to Purchase a Good Generator. Who is the audience, and what is your book’s main message? Jiří Ruml: One of the directors and cofounders of Mavel asked me to consider writing a book that would help younger colleagues at the company improve their knowledge in the field of hydro generators. The book describes the principles of operation of the synchronous generator, parameters such as efficiency and reactance, measurement methods, and generator design and includes operating diagrams and characteristics. Mavel needs such knowledge when requesting or assessing proposals from generator manufacturers and when evaluating the parameters of hydro alternators that have already been produced. Hydro Leader: You have designed more than 70 customized hydro generators. What are the main lessons you learned through that experience, and how did you approach change? Jiří Ruml: Yes, I designed about 70 hydro generators, which are still in operation in power plants in the Czech Republic and abroad. In addition to classic generators of vertical and horizontal design, I designed hydro generators for pumped storage power plants. I developed software for asynchronous startup for pump operation for both pole sheets and massive poles. These generators ranged from 50 to 100 megavoltamperes (MVA). I designed a hydro generator with a maximum power equal to 355 MVA, 22 kilovolts (kV). Two hydro alternator units of this type are still in operation at the Dlouhé Stráně pumped storage power plant in the Czech Republic. Hydro Leader: What sorts of technological changes have you seen and experienced in the hydro field during your long career? Jiří Ruml: During my career, there has been an increase in the power performance of generators. The materials have been used more efficiently. Manufacturers have used higherquality stator magnetic circuit sheets as well as higherquality winding insulation. I have always incorporated these changes or innovations in my design work.
PHOTO COURTESY OF MAVEL.
Hydro Leader: What are the most important lessons you have learned over your career? Jiří Ruml: In my opinion, the most significant task in my career was the design of a 100 MVA motor-generator for a pumped storage project. The challenge was to design asynchronous startup using the damping winding of the generator poles for pump operation. The second most important task, and the one I valued the most, was the hydroleadermagazine.com
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design of the 355 MVA hydro alternator for the Dlouhé Stráně pumped storage power plant. In this particular case, it was no longer possible to use asynchronous startup; instead, the alternator used an asynchronous motor directly on the unit shaft. This generator was also exceptional because the stator voltage was 22 kV and the winding was cooled by distilled water directly in the hollow conductors of the stator winding. The thermal expansion of the upper bracket’s arms was regulated by a computer in order to avoid any undesired pressure in the concrete structure of the power plant. Hydro Leader: What is your vision for the future of hydropower? Jiří Ruml: Unfortunately, at my age, I do not really have any significant prospects for the future of my career. However, I am thrilled that I can work with the Mavel team and share my extensive professional experience in the field of hydro generators. The development of hydro dams can be quite complicated and very much depends on terrain conditions. It tends to be most economically feasible to build power plants with higher installed power (that is, with generators of approximately 100 MVA) in mountain areas with higher heads, lower population density, and a minimum agricultural production. In countries with rather flat terrain, it is important to assess the advantages and disadvantages of developing new hydropower plants. Some argue that one of the disadvantages of building hydropower plants is their effect on the environment. On the other hand, there are also significant advantages. First, as I have already mentioned, hydropower does not produce any undesired emissions and is thus environmentally friendly. Second, dams can also provide water storage, which may be critical during droughts. Finally, dams also protect against floods. In countries with flatter terrain, we are generally speaking about power plants with lower installed power and generators in the 5–20 MVA range, suitable for small rivers. In general, I see a huge potential for hydropower today because it is an emission-free source of energy. In my opinion, hydropower plays a key role at the present moment, when the price of electricity is growing fast and global society needs to decrease the volume of undesired emissions produced by steam power plants in order to protect and maintain a healthy environment. H Jiří Ruml is a generator expert at Mavel. He can be contacted at ruml@mavel.com.
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