Electrical substation is electrical equipment intended for reception, transformation and distribution of electrical energy, consisting of transformers or other converters of electrical energy, control devices, distribution and auxiliary devices.
In the implementation of modern technological progress has an important role of electrification. The application of electric power in any industry can increase productivity, to achieve a high level of mechanization and automation. Powerful development of the electricity base provides a solid background for further development of industries, agriculture, and transport. But all this is impossible without high-quality and uninterrupted supply of electric energy consumers, whether industrial plant, agriculture or population. Especially now in our difficult economic situation it is necessary not to lose and even try to raise the level at which we have is the power supply. And this cannot be done without having competent, well-trained professionals.
The main prerequisite for the development of the first electric DC networks was the discovery of the electric arc by Professor Vladimir Petrov in 1802. In the process of their experiments of the Russian scientist drew attention to the brightness of the light effects in the event of an arc, and indicated the possibility of using it for lighting. However, several decades passed before the electric arc received practical use as a light source. The practical electric light source first decided Yablochkov in 1876 invention of his “electric candles”. At the same time, another Russian electrician Alexander Nikolayevich Lodygin created the incandescent light bulb, subsequently superseded “Yablochkov candle”. The emergence of such practical light sources like incandescent largely contributed to the development of electrical networks. Since the network was originally designed for street lighting, but due to the fact that the load of these networks was not uniform, because the lights only worked in the dark, to the networks began to connect the various production facilities, where at that time was used or installed electrical equipment, operating at a constant current (motors, galvanic baths). Together with the increasing number of electricity consumers have increased power stations, and more clearly the trend of centralization of power.
The famous American inventor, and industrial worker Thomas Edison (received over a thousand patents in the U. S. and about 3,000 in other countries) in 1878 founded the Edison electric light» (the now famous group General Electric). By 1879, over lapping invented light bulbs — one bulb has served more than 12 hours. In 1880, Edison patented the whole system of production and distribution of electricity at a constant current, which included three wires — zero and ±110 volts (this reduced the consumption for the same energy loss). At the same time was demonstrated unprecedented lifetime of the bulb is 1,200 hours. That's when Edison said, «We will make electric light so cheap that only the rich will burn candles». In January 1882 Edison launches the first power station in London, and a few months later — in Manhattan. By 1887, in the U. S. there were more than hundreds of DC power is working on a three-wire Edison system.
Unlike Edison, who proved himself a tireless experimenter and a skilled businessman, but not a theoretician, supporters of AC thoroughly knew mathematics and physics.
Knowing all the advantages of alternating current over constant, after reviewing the patent Edison George Westinghouse (American industrialist, engineer and entrepreneur, the founder of the company «Westinghouse electric») found a weak link in his system — large power loss in the wires during the transmission of electricity over large distances with low voltage. This is due to the fact that, with increasing distance, increasing the electrical resistance of the wires and increasing the loss on heating. In the construction of electric lines, designed for transmission of a certain power, significantly reduce loss is possible only by reducing the resistance (making the wire thicker) or increasing the voltage (reducing, thereby, the strength of the current). To four times to reduce losses, we have a fourfold to reduce the resistance by increasing the same cross-section wires or twice to raise the voltage in the same section. Thus, the transmission of power over long distances is only possible when using high voltage.
Because effective ways to change the DC voltage at that time did not exist, in power plants Edison used DC voltage close to the consumer — from 100 to 200 volts. Such plants are not allowed to transfer to the consumer considerable power over long distances. As a result, effective use of the generated electrical energy can consumers located at a distance not exceeding about 1–2 km from the power plant. To overcome this limitation could have been complex and expensive measures: the use of heavy wire or the construction of a network of local power plants. In other words, the approach of Edison was not allowed to build a powerful power plant, supplying the whole region, as well as to build a hydropower station in the proper position.
The only solution to the problem of transferring power over long distances without significant losses was the transition from DC to AC. However, at this point there was no motor running on alternating current. Even in the early 80-ies of the electricity consumed mainly for power needs. DC electric motors for driving various machines were used more and more often. To create a motor that could run on alternating current has become the main task of electrical engineering. It was during this period and began the search for a solution to this problem Nicola Tesla. Nicola Tesla proposed a radical solution to the above problems, immediately appeared acceptable for practical purposes. Tesla imagined that if any way to supply the windings of the magnetic poles of the motor by two different alternating currents differing from each other only by a phase shift, the alternation of these alternating currents will cause the formation of the North and South poles or the rotation of the magnetic field. The rotating magnetic field must captivate and the rotor winding of the machine. Having built a special two-phase source current (two-phase oscillator) and the same two-phase motor, Tesla carried out his idea. And although it constructively machines were very imperfect, the principle of the rotating magnetic field applied in the first models of Tesla, was correct. Having considered all possible cases of phase shift, Tesla has focused on the shift of 90°, i.e. two-phase current, creating a two-phase generators and motors, and only briefly mentioned in their patent applications of multi-phase currents and their application. Because of these developments, Tesla introduced the possibility of transmission of electrical energy over long distances, and therefore the construction of the power plant centralized power supply. So, for example, 1883 at Niagara Falls was laid a large hydroelectric power plant capable of producing two-phase alternating current capacity of 75 megawatts, which is enough to light the city of Buffalo.
And at the same time in Berlin of the brilliant Russian engineer Mikhail Dolivo-Dobrovolsky was studying three-phase alternating current. At the time of construction of the Niagara power plant Dolivo-Dobrovolsky were created, three-phase motors and generators, developed drawings of three-phase transformers. Tests created by Dolivo-Dobrovolsky equipment operating on three-phase alternating current, showed that this type of current has significant advantages. It turned out that with a substantial improvement of the magnetic properties of the generator and the engine was significantly decreased and the consumption of copper in transmission lines. Connected three-phase system required only three wires in contrast to the decoupled three-phase system proposed by Tesla, which required six wires.
The simplicity of construction and reliability in operation three-phase motor with squirrel-cage rotor, designed Dolivo-Dobrovolsky has ensured that the engine since the invention up to the present time the most widespread in the world compared with other known types of engines.
In the middle of 1891 was completed the construction of a transmission line over a distance of 175 kilometers, equipped with a hydroelectric power plant in Laufen, which set three phase generator with a capacity of about 190 kilowatt step-up substation and step-down substation in Frankfurt. On 25 August 1891 at the exhibition for the first time on fire, about 1,000 electric light bulbs, and on September 12 was included and asynchronous three-phase AC motor, causing the pump to supply water to decorative waterfall.
The test transmission line and the whole system were initiated by the international Commission in October 1891, and showed that when the voltage in the transmission line 15 thousand volts efficiency reached 75.2 per cent. Particularly tested at high voltage, comprising 28 thousand volts, at which the efficiency was 78.9 percent.
This was a huge achievement in electrical engineering demonstrated the practical feasibility and economic feasibility of applying the developed mo Dolivo-Dobrovolsky systems and electrical machines three-phase alternating current.
And as we know, the AC voltage is easily adjusted up or down using transformers (efficiency of modern power transformers up to 99 %). This gives the possibility of using step-up transformers are installed in the transformer substation near the power generators, to pass current through main lines of very high voltage over long distances (hundreds to thousands of kilometers). With the help of step-down transformers, AC electric power is also easily transformed into a network of high voltage lines less voltage to supply power to other transformer substation, and then to the final consumers of low voltage current (in our country — 220/380 V).
Due to its properties of an alternating sinusoidal current is more versatile and is adapted to solve other than lighting, industrial and domestic tasks. For example, the vast majority of electric motors (total power) used in all branches of industry, transport, construction, agriculture and household appliances are three-phase or single-phase asynchronous motors. This is due to the simple design of these engines and, consequently, their efficiency and the highest reliability and durability compared to other types of engines at a sufficiently high energy performance. It would seem that all options for optimal power transmission over long distances in our time exhausted, and the question arises: are there any prospects for a more favorable energy transfer? Of course, they have, since humanity is not static, and new materials with new properties, new properties of already known materials under various impact and in this case we are interested in superconductors. Actually, superconductors as a special material do not exist. It's the usual materials of the elements of the periodic table, in which in certain conditions appear unusual properties. Aluminum, for example, is considered a good conductor; good heat skips and in their thickness slightly increases the magnetic field (paramagnetic). When cooled below 1.2 K, the electrical conductivity of aluminum increases infinitely (superconductor), the thermal conductivity is as much worse (insulator), and the magnetic field it can't get (diamagnetic). It would seem that the attainment of such useful qualities needs to pay too expensive — the achievement of low temperatures is not cheap.
After the discovery of the phenomenon beyond thermal conductivity at the temperature of liquid nitrogen and the creation of superconducting materials to implement the idea of power transmission without losses began Russia, USA, Japan and several other countries. They began to design and build a pilot line using superconducting underground cables. The first of such lines was made and tested in the USA. Now there are in experimental mode, the cable length of 100 meters on the Island of Log Island. The next phase of the U. S. program in the framework of the project «Hydra» paves superconducting transmission lines in Manhattan and associates them with the power systems on the mainland of New York. An example of the application of superconducting cables in Moscow may be the supply of a tall building complex «Moscow-city». Physicists Kurchatov Institute managed to solve the problem of the cable manufacturer with almost an ideal material structure and quality of production. While their length is limited to a few kilometers, but in the future it is possible to manufacture cables of a superconductor with a length of tens of kilometers. Then superconducting electrical networks, you can associate the individual objects and entire regions.
References:
1. V. V. Krasnik operation of electric power substations and switchgears, 2012
2. L. Drokova, L. K. Karneyeva, Chirkova T. V. an electrical power stations and substations tutorial, 2013
3. https://ru.wikipedia.org/wiki/ %dd %eb %e5 %ea %f2 %f0 %e8 %f7 %e5 %f1 %ea %e0 %ff_ %ef %ee %e4 %f1 %f2 %e0 %ed %f6 %e8 %ff
4. I. G. Fence, PhD. Tech. Sciences, associate Professor, technical articles. — electric networks. The history, current state and prospects of development.2011
