Resistance is futile


 

Energy systems in the modern state can be compared with the circulatory system of a living creature. On how to make it more "ongoing", we decided to talk to the deputy scientific director of JSC "FGC UES SEC" Doctor of Technical Sciences, an expert in the field of superconducting materials iustroystv Victor E. Sytnikova

 

Small cable, but the roads

 

— Superconductivity was discovered in 1911 by Dutch scientist Heike Kamerlingh Onnes. Prior to the 1960s. it was purely academic phenomenon that just studied and tried to understand its nature. Only in the 1960s. There are the materials from which it was possible to do something practical superconducting, but they had to be very cool. As refrigerant used liquid helium boiling point at atmospheric pressure — 4.2 Kelvin. This direction has been quite rapidly. Were created by the huge plant. Known to you the Large Hadron Collider is working on superconducting magnets. Now in France built a fusion reactor ITER, created a series of smaller-scale superconducting systems. The first was our domestic superconducting tokamak T-7, created at the Kurchatov Institute, the last units were built in Korea and China. This is a huge machine. But due to the complexity of it all was far from a real industry and energy, is only suitable for laboratories, where plants have worked very qualified people. And the work itself in plants was not constant, and the series was conducted. Zaholodili installation, run, worked three or four months, and then process the results of a few months, then the next series. In 1986, she was the discovery of high-temperature superconductivity, for which Karl Mueller and Georg Bednorz won the Nobel Prize. Generally for superconductivity received several Nobel Prizes.

— Pyotr Kapitsa, too, for it was?

— Not really. Pyotr Leonidovich received it in 1978 for the discovery of svertekuchesti liquid helium. But we can say that this discovery in a related field. Here the main winners for us, Alexei Abrikosov and Vitaly Ginzburg. They, along with Anthony Leggett received the award in 2003 for "pioneering work in the theory of superconductors and superfluids." When they opened the high-temperature superconductivity, it is possible to cool superconductors with liquid nitrogen. And this is not the liquid helium. The latter, when vaporized, flies into the upper atmosphere, and it is almost impossible to get, ie there can only be closed systems. A nitrogen we are practically breathe in air, 75% by weight, it is inexpensive and the liquefaction is used very widely. Therefore, the discovery of superconductivity revived interest in the real industry, in electrical engineering. However, early enthusiasm over a decade, frustrated by the poor performance of materials that at these temperatures were superconducting. By passing a current through them or when they enter the magnetic field that is interconnected, superconductivity is destroyed. Only at the very end of the last century materials have been developed, of which something can be done. Then the concrete work had already begun in many areas.

— For what?

 

— For electrical engineering major I would call a superconducting current limiters, superconducting cables, superconducting transformers, generators and electric drives. There are some common industrial applications. Tomography for low-temperature superconductors are available now in large numbers — about 3.2 million a year. Created the first set by induction heating with superconducting magnets, has separators with superconducting magnets. Thus, slowly but surely, this technique is in the industry.

— What gives superconductivity in power?

 

— Superconductor conducts direct current without resistance. Alternating current is little resistance, but it is associated with a reversal of losses, the penetration of the magnetic field in the material. And it is a constant zero. Plus, of course, enormous current density. If we copper power cables of about 1 A per square millimeter, home wiring — 5.10 A, the high-temperature superconductors it reaches 100-200 amps per square millimeter. And in the superconducting layer are already millions of amperes per square centimeter. But they made only very thin — 2-4 microns thick.

— Cables are minimized?

— Including one. You can make a very effective and very compact device. We are now making huge trunking to take power from the generator to the power plant and bring it to the transformer, which will raise the voltage up and down the transmission line will transmit to consumers. At high power requires huge trunking section under square meter. And they can be replaced fairly compact superconducting cables. It is now the most superconducting cables are close to implementation.

— What did they give?

— The sharp decline in energy loss and increase the unit capacity. Instead of the usual dozen cable lines can be laid one to two. On average, the superconducting line can transmit three to four times more power than regular same dimensions.

— But usually not necessary to cool.

— So think people who are unfamiliar with the topic. Conventional cables are powerful too cool, sometimes oil, sometimes the air in the tunnels. Always required to provide heat, as when the current in the traditional conductor he always heated and maximum heat insulation performance is limited.

30 further

— But in order to get things matter, we must first construct an experimental demonstration cable line.

— It is already there, and not one. In the world created by a number of lines. who have already worked deadline. The first small lines at 30 m were put on trial operation in the United States and Denmark back in 2001 The very first in the state of Georgia, is working so far. Others removed from service.

— Why? Broken? Did not survive?

— Sustained, not broken. Simply, they accomplished their mission. This is not an end in itself, it was a demonstration of the capabilities and reliability. In Ohio, at the substation "Bixby" for about ten years on the order of a large line of the order of 350 m and is reliable. About the same line in the city of Albany in New York State, worked six or seven years, then was decommissioned. The tasks they are set, have been resolved.

And we have that?

— Our business is moving too, although not as fast as we would like. Back in RAO UES became interested in superconductivity. The first funding was from them, and the first industrial experiments took place under their auspices. But the real projects went with the Federal Grid Company. The first project — the creation of AC superconducting cable length of 200 m Our organization makes it the most

active participation. We have created a test bed on which to test the long cable lengths at full load. Next we have the following program is the creation of a line of constant-current. The first project, a demonstration, it will be according to the plans in about two years, installed at the substation "Dynamo" and bypassed conventional cables.

— And the second?

— The second project is 2.5 km, about the same time, must be placed in St. Petersburg. This is a real line connecting two substations.

— What is the purpose of the second project?

— All of the power system, especially in large cities, are partitioned. They can not be joined into a single multiply-connected network, because it is very greatly increased short-circuit
currents. A breaking capacity of all of the world’s switches — 61 kA at high currents very likely damage. In Moscow, there are rings 110,220 and 500 kV. In the rings 110 and 220 kV, about a hundred of crosscuts. And these rings are from the station so-called deep input. They may be very close, often within 200 m, and a short connection between them, just across the ring. But when communicating through a ring of his big problems arise. Some examples could include blackout that occurred recently in St. Petersburg. On one of the substations was an accident — she passed out. There was a rush current in a nearby substation. There’s nothing there, there’s just this operate, and it is also disconnected. And so it turns out that what we call the rolling blackouts. If these stations have been in contact with each other at low voltage, then none of this would not happen. The nearby station to energize the network de-energized, and that all would be over. But now they can not be bound by conventional AC lines because it increases short-circuit currents. But the line of the DC link can be. It’s something like an insert that we have is on the border with Finland. But there simply insert rectifier and inverter, and there is still need to connect the substation, located at a distance. In order to connect the substation need decent power. A decent power by typical cable — this is some excavation will be so many that it’s better to eliminate the accident. The joke, of course. Plus a large number of fairly expensive cable. And there is a good solution: superconducting cable and DC-DC converter with a rectifier side, on the other — inverter.

— It turns out that such a relatively small piece of superconducting cable solves many problems?

— Yes. In general, it is a dream of Power — tie in big cities such deep inlets superconducting ring. This is an order of magnitude increase the reliability of power supply. Right now we are doing this. OAO "UES FGC" raises the issue seriously enough. The task is not to make a cable and demonstrate on the test bench, that it works for a month or somewhere and then put off. It is necessary to create for him a whole set of equipment. This cryogenic plant to be cooled with liquid nitrogen and its pump by cable.

— A vendor-nitrogen does not use?

— It is possible. It is not so important. But their own nitrogen — it greater autonomy. The system must be closed, and the refrigerant pump cable should the entire length. There are a lot of its hydraulic problems. We must create a certain pressure, a certain flow to remove heat leakage. because in a cryostat heat still comes to the cold zone. Plus the need to build a rectifier and inverter stations, provide a diagnosis, communication with the grid, set the matching transformers if necessary — filter-device. It is this complex, and we are now developing. Already established cooperation, industrial enterprises engaged in the production and cable and converter, and Refrigeration.

Once the strip, two strip

 

— Do we have now an industrial enterprise which is engaged in high-temperature superconductors?

— We still do not themselves manufacture of superconducting materials, we buy them abroad. As for cryogenic technology — we have since Soviet times were the two current flagship "Cryogenmash" and "Geliymash." We are working with the Moscow "Geliymash", they make a lot of equipment for metallurgy, machinery for spaceports, producing liquid hydrogen and oxygen. As for the manufacture of the cable itself, then in principle it can be done on any cable plant. We need a skilled technologists who know how to deal with the superconducting material and designers, all of which will count.

— But there is also some of his characteristics?

— Of course. If conventional cables major problems are concentrated in isolation, the superconducting cable in the current-carrying conductor. At present, the unit has lived 100-200 A, and from them it is necessary to dial 2.5-3 thousand A. In conventional cables that question is easy to solve. You take the wire of the same length and cross-section of intertwining them — and the current is distributed evenly over them, because the resistance of the wire is almost equal. But in superconducting wires no resistance. If you wove them, then you do not know how to distribute the current. At the end of the 1990s. in America and in Japan there was a whole race for who will make the first piece of cable with the best characteristics. Then the two Japanese companies Furukawa and Sumitomo, and one American Pirelli, made the 50-foot pieces. They used about the same current-carrying ribbon and twisted them in several layers, to gain current. Everyone wanted to get somewhere 2 — kA. Furukawa made ten such layers, Pirelli — six, Sumitomo — four. They have all experienced them and got the same current regardless of the number of the superconductor. All this became clear already then physically. We have published on this topic and a series of works have shown that as much as they do (and they do wrong) they have current flowing in only two layers of tape, so everyone got the critical current of the two surfaces, and all the layers at the bottom just do not work. Now this was sorted out, there are already patents solutions. Issues in this area is not, and tapes have become better. We are now doing up to six layers with no problems, and all the layers evenly filled with shock.

— So, the scientific problems are more or less solved. And as with high-voltage?

— Liquid nitrogen — a very good insulator. If it is under pressure it acts as a better insulator than transformer oil. So there is no problem. We recently hosted the test — have prepared a series of samples of the DC cable and tried their "break". We insulation thickness of about 4 mm, and we did 0.7, 1, 1.5, 2 mm, etc. We took a set of up to 70 kV and thickness of 0.7 struck at around 47 kV. Millimeter taken — no longer breaks. Of the three samples one struck a 68 kV, and two and 70 kV is not broke. It surpasses all of our state standards. While we had liquid nitrogen at atmospheric pressure, and the cable it is pressurized. At atmospheric pressure, bubbles can be formed, and when we it is pumping pressurized cable, there is no bubble, i.e. dielectric strength there will be even higher. It turns out that the problems with living solved the problem with insulation solved, questions remain about the organization of production and gain experience. Because the energy, of course — a very conservative area.

— But it is supposed to be such because of it very much depends.

— Of course. And in order to expand the business on a large scale should be operating time. We hope that 2014 will produce the 2.5 km of cable, 2015 will prepare the infrastructure and lay him right in the center of St. Petersburg, near-channel. There’s a tunnel dug between the two substations, and if you are ready, then in 2015 we will deliver. And it will operate without the bypass conventional cables 2.5 km. The transmit power on it will be 50 MW, which is very unusual for traditional energy: at a voltage of 20 kV is usually transmitted not more than 10-15 MW. And this is not the limit. Direct current can be passed 150-250 MW.

So, this line replaces at least four?

— It replaces a lot of lines. And you have heard, perhaps, that everyone is talking about smartgridah, intelligent networks, etc. What is the normal AC line? You attach the line to two points and you just can not influence it. Where there is a current will flow, depends on the pote
ntial at these points. And when you have a line of DC, you also have converters, it has adjustable line. Thus, you can control the flow of power until forced change of direction from point A to point B and from point B to point A. Since all systems are rather multiply, if you include in it the superconducting line, it is the smallest resistance and it takes over the maximum load. Loss it is almost there. So, we get a transfer efficiency of 99% on AC. At a constant bit worse, because the energy is lost in the converters themselves. Thyristors are heated, it turns out that in them we lose about 2%. But it is still infinitely less than the losses in distribution.

— Loss of 2% — is, as they say, "the margin of error."

— In general, I believe that together with the thermal losses, with thyristors we are on 3%, and it is much better than any other system, including the high-voltage gas-insulated. Nowhere is the loss below.

Elementary highway

— I’m just about imagine how the ordinary superconductivity, but was never able to understand how the high-temperature superconductivity. In normal, as I understand it, the crystal lattice, "freezing", freezes, and electrons get very broad way, a kind of a line through which you can skip, without hindrance. But in the high-what’s happening?

— You do not have exactly the right idea. In the low-temperature superconductivity lattice is not completely "freezes". It responds to the electrons and phonons through the exchange of electrons with the lattice two electrons are bound together form the so-called Cooper pair. And here they are already moving through the lattice without resistance. If you want to know exactly the mechanism of high-temperature superconductivity, I wish you success, because it is the next Nobel Prize: to the end that is not described or understood. There is a hypothesis, it has been suggested, but there is a little bit different situation. If the low-temperature superconductors we dimensional conductivity, there must be a structure of the planar material — i.e. on the planes. Basically, copper and oxygen atoms form a plane along which there is movement, so in two ways, say, depending on the field, it is about the same as in the third direction — is across the planes, everything turns out much worse.

— So, here is my comparison to the highway close to reality. The concrete surface of the machine they ride like the wind, but through it is so easy to not break.

— High-temperature superconducting material is very sensitive to the magnetic field. Even if it is cooled down to liquid helium, he still remains very sensitive to the transverse magnetic field. In principle, this is one of the reasons why the cables have been great power: they have such a configuration, the magnetic field is always parallel to the surface. In any winding always ends have components perpendicular to the surface, and it’s hard "cuts" the current-carrying capacity. A circumferential component cables in parallel to the surface, so a high density of cables and current. respectively. capacity. Already set up cables and hundreds of megawatts under great stress. China has launched a line of constant current, transmitting 10 million and at a distance of about 800 meters from the substation to the aluminum smelter.

— That is, the Chinese have been active here, too?

— Not really. They are quite a long time, five or six years ago, made two small AC line and that’s retarded. More a thing of the current limiters. Only now they have created a good postoyannotochnuyu line. True, at first they announced that she will be 20 kA. but in the end it turned half. Honestly, Russian specialists have reached 10 kA for the first time in 2000 However, not at home, and under contract in Mexico. Everyone understands that these cables a huge advantage. When a low voltage high current can pass, removes the need to build huge increase substation, because the same power can be transferred to a lower voltage.

— And why is such a great line while building such quiet pace?

— Where to build? Infrastructure, it is already set up, and get into it with a piece of superconducting, ie, high current and relatively low voltage, it is difficult, because require a lot of matching devices. This is good for new facilities, which should be one for the transfer. But in order for it to build something, it is necessary that it is already working somewhere and showed its efficiency and cost-effectiveness, or just no one dares. And rightly so. An example of a large-scale project using low-temperature superconductivity-cable for ITER.

— How much is the production of such a cable?

— It is much cheaper than the cost of the material itself every five. Because each wire has about 8 million fiber diameter of 4.5 microns. And from end to end for miles, these fibers should not be torn. All this is done in Russia. Low-temperature superconductors, we are very good. We hope that soon there will be a good high temperature. Now "Rosatom" adopted the program and took on the task of developing these high-temperature materials.

Superconducting supertormoz

— I already told you a lot about the cable because we’re doing it. Nov believe that widespread adoption of energy in the most promising superconducting current limiters.

— Superconductor current limit current? This is something out of the field of paradoxes.

— There are no paradoxes, all elementary principle of operation is much simpler than any modern tokootklyuchayuschy machine. When somewhere along the line short circuit, we have the standard operation of relay protection is 200 milliseconds, ie, on the equipment to the first half-wave maximum amplitude (peak current), then the time to go through a few large-amplitude waves, and only a trace of fire protection. This peak current is very harmful to the equipment, as leads to increased electromagnetic and electrodynamic effects on him. By the way, one of the major causes of failure of transformers, just mechanical loads during the passage of the surge current. Superconducting current limiter is the only option. which allows you to cut the peak current, because there are no actuators, it is just a property of the material. Initially, the resistance is zero. In sharp than the critical value of the current superconductivity disappears instantly, therefore, the resistance grows to several orders of magnitude. In fact superconductor almost instantly turns into a resistor. Such a current limiter response time, depending on the rise time, two to five milliseconds maximum. And it is great to have the first wave of cuts.

And the military is the application of superconducting technology for?

— And not one. The first is a low-speed engines. that do not require a manual transmission, which means noise reduction for submarines. Furthermore, they are much easier. Already created the engine for 36 MW, it is about five times lighter than normal. But they are still working at low temperatures up to 30 ° C. There are projects with a superconducting magnetic catapult that can be used on an aircraft carrier to launch aircraft. Uninterruptible power supplies on the basis of superconducting inductive energy storage devices are used for emergency power communication centers, headquarters, launchers and other objects. Inductive energy storage devices are also used to power the pump lamp power pulsed lasers. Quite a lot of the so-called low-current superconductivity is used in space — all kinds of detection systems, bolometers, sensors … After all, what is the sensitivity? This ratio of useful signal and noise. And the noise is reduced at low temperatures. Furthermore, the use of quantum effects in superconductors allows several orders o
f magnitude greater sensitivity and accuracy of the sensor instrumentation. Therefore, low temperature superconductors are used in antennas. Superconducting antennas are very sensitive, even when not used in space and on Earth. So, if we ever establish a connection with aliens, most of all, we will help in superconductors. |

In the world of science 6.2013

Interviewed by Valery Chumakov

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