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Voltage in the contact network rzhd. History of railway electrification
2. Electric power supply systems railways, enterprises of railway transport and modes of their work.
2.1 Brief history and current state of railway electrification.
2.1.1 History of electric traction.
The first EZhD was demonstrated in 1879 by Siemens in Berlin at an industrial exhibition. An electric locomotive with a power of 2.2 kW carried three cars with 18 passengers. In St. Petersburg in 1880, experimental trips were made for a 40-seat carriage with an electric motor of 3 kW. In 1881 the first tram line began to operate in Berlin. In Russia, the first tram was put into operation in 1892. The first section of the railway with electric locomotive traffic was opened in the USA in 1895.
2.1.2 The main stages of the electrification of railways in Russia. electrification plans.
The electrification of Russian railways was planned by the State Plan for Electrification (GOELRO) in 1920. The first direct current electric railway with a voltage of 3 kV Baku - Sabunchi was launched in 1926. In 1932, the first electric locomotives went through the Suram pass in the Caucasus. By 1941, 1865 km were electrified. During the years of the Great Patriotic War of 1941 - 1945, the electrification of railways continued: the sections Chelyabinsk - Zlatoust, Perm - Chusovskaya, etc. The electrified section Murmansk - Kandalaksha worked steadily in the front zone.
The master plan for the electrification of railways in the USSR was adopted in 1956. Since this year, the rate of introduction of electric traction has significantly increased.
The rates of electrification in the USSR were:
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Kilometers |
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At the beginning of 1991, 55.2 thousand km were electrified. Of the 147,500 km of railways in the USSR, this amounted to 37.4%. The volume of transportation on electric railways was 65%. Thus, 1/3 of the railways are electrified, and 2/3 of the goods are transported on them. As a rule, the busiest directions were electrified. Such a ratio of railway electrification and transported goods indicates a significant efficiency of railway electrification.
The length of electrified railways by years:
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Total, thousand km |
On alternating current, thousand km |
length, in % of total length |
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In Russia | |||
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Electrification plans | |||
The following railway lines operate on electric traction:
Vyborg - St. Petersburg - Moscow - Rostov-on-Don - Tbilisi - Yerevan, Baku - 3642 km.
Moscow - Kyiv - Lvov - Chop - 1765 km.
Moscow - Samara - Ufa - Tselinograd - Chu - 3855 km.
Brest - Minsk - Moscow - Sverdlovsk - Omsk - Irkutsk - Chita - Khabarovsk - Vladivostok - 10,000 km. In 2002, the electrification of the Trans-Siberian Railway was completed.
Ufa - Chelyabinsk - Omsk - Irtysh - Altai - Abakan - Taishet - Severobaikalsk - Taksimo
Until 1956, the electrification of railways was carried out exclusively on direct current, first at a voltage of 1.5 kV, then at 3 kV. In 1956, the first section was electrified on alternating current with a voltage of 25 kV (Ozherelye - Pavelets section of the Moscow road).
The stage of transferring electric traction from direct current with a voltage of 3 kV to alternating current with a voltage of 25 kV has begun.
In November 1995, for the first time in the world practice, the main section of the Zima-Slyudyanka railway, 434 km long, was switched from 3 kV DC to 25 kV AC. At the same time, two docking stations were eliminated. This made it possible to increase the weight of freight trains. A single continuous highway Mariinsk - Khabarovsk was created with a length of 4812 km and 2002 to Vladivostok, electrified through the power supply system alternating current 25 kV. In October 2000, the section Loukhi - Murmansk with branches (490) km of the Oktyabrskaya railway was transferred to alternating current.
Statistical information on the electrification of Russian railways:
by length: diesel traction - 53.2%, electric traction - 46.8%;
in terms of transportation volumes: diesel traction - 22.3%, electric traction - 77.7%;
by types of current: direct current with a voltage of 3 kV - 46.7%, alternating current with a voltage of 25 kV - 53.35%;
The share of electrified railways in Russia in the world:
by length from the total railway network of the world: Russia - 9%, other countries of the world - 91%;
by the length of electrified railways: Russia - 16.9%, other countries of the world - 83.1%.
The program for the electrification of railways and the switching of freight traffic from diesel to electrified runs provides for the electrification of 7640 km and the transfer of approximately 1000 km of railway lines from direct current to alternating current in the period from 2001 to 2010. At the same time, 90% of the new electrification is carried out on alternating current and only a few branches on direct current. By 2010 Russia will have 49.1 thousand km of electrified lines. This will amount to 56.7% of the total length of the railway network, while performing 81.2% of the total volume of traffic on it. Russia will fall into the area of the most optimal use of electric traction
The introduction of electric traction has the following stages:
1. Electrification of suburban areas at a direct current voltage of 1.5 kV;
2. Electrification of the main sections of the railway with a voltage of 3 kV and transfer to a voltage of 3 kV of suburban sections.
3.Introduction of alternating current with a voltage of 25 kV along with the expansion of the polygon of direct current with a voltage of 3 kV. A reliable system for joining two types of current by sectioning the contact network has been developed.
4. Implementation of a three-wire autotransformer power supply system of increased voltage 2x25 kV and reduction of electrification at direct current 3 kV.
5. Transfer of sections of direct current to alternating current.
In the last quarter of the XIX century. the contours of new areas of locomotive building were outlined - electric locomotive and diesel locomotive building.
The possibility of using electric traction on railways was indicated back in 1874 in an application for a privilege by the Russian specialist F. A. Pirotsky. In 1875-1876. he conducted experiments on the Sestroretsk railway on the transmission of electricity along rails isolated from the ground. The transmission was carried out over a distance of about 1 km. The second rail was used as the return wire. Electricity was transferred to a small engine. In August 1876, F. A. Pirotsky published an article in the Engineering Journal with the results of his work. These experiments led him to the idea of using electricity for trolleys moving on metal rails.
The practical implementation of the idea of using electric energy in transport belongs to Werner Siemens (Germany), who built the first electric railway, which was exhibited at the Berlin Industrial Exhibition in 1879. It was a small narrow-gauge road intended for walking exhibition visitors. A short train of open trailers was driven by an electric locomotive with two motors, which received D.C. voltage of 150 V from an iron strip laid between the rails. One of the running rails served as a return wire.
In 1881, W. Siemens built a trial section of an electric road in the Berlin suburb of Lichterfelde, using a motor car for the first time. A current of 180 V was supplied to one of the running rails, and the other rail served as a return wire.
In order to avoid large losses of electricity, which arose due to the poor insulating ability of wooden sleepers, V. Siemens decided to change the electric power supply circuit of the electric motor. For this, an overhead working wire was used on an electric road built in the same 1881 at the Paris World Exhibition. He represented an iron tube suspended above the rails. The lower part of the tube was provided with a longitudinal slot. A shuttle ran inside the tube, connected through a slot to a flexible wire, which was attached to the roof of the locomotive and transmitted electric current to the electric motor. The same tube, suspended next to the first, served as a return wire. A similar system was applied to those built in 1883-1884. suburban trams Mödling - Vorderbrühl in Austria and Frankfurt - Offenbach in Germany, operating at a voltage of 350 V.
Around the same time, in Kinresh (Ireland), a third rail was used on a tram line, which was installed on insulators next to the running rails. However, this system turned out to be completely unacceptable in the conditions of the city, interfering with the movement of carriages and pedestrians.
It is interesting to note that the technical doom of such a system for supplying electric current to the motor was foreseen earlier by F. A. Pirotsky, who wrote in 1880 in the newspaper S. Petersburg Vedomosti: “The electric railway built by me is the simplest and cheapest. It does not require the cost of the middle rail line, needlessly increasing the cost of the road by 5% and stopping carriage traffic in the city. It does not require the cost of cast-iron poles, which are prohibitively expensive.
This letter was published by Pirotsky in connection with reports that appeared in the press about the results of tests of an electric tram carried out by him on September 3, 1880 in St. Petersburg. At this time, F. A. Pirotsky was intensively engaged in the implementation of his projects related to the creation of reliable urban electric transport. He understood that the development of the main railway electric transport is impossible without solving the fundamental problem of electrical engineering - the transmission of electricity over long distances. Taking this into account, F. A. Pirotsky concentrated his attention on the experiments on the electric movement of the car, adopted on urban horse-drawn railways. As a result, in 1880 he managed for the first time to carry out the movement along the rails of a real two-tier motor car. F. A. Pirotsky presented the results of his work in 1881 at the International Electrical Exhibition in Paris, where he exhibited his scheme of an electric railway.
In 1884, in Brighton (England), an electric railway was built according to Pirotsky's scheme, powered by one of the rails, 7 versts long. The operation of only one wagon gave a net profit, compared with 420 francs a day horse-drawn.
Since the mid 80s of the XIX century. The development of electric traction on railways is beginning to be intensively engaged in by American engineers and entrepreneurs, who energetically set about improving electric locomotives, as well as methods of supplying current.
T. A. Edison worked on the problem of electric railway transport in the USA, who built three small experimental lines during the period from 1880 to 1884. In 1880, he created an electric locomotive, which in its appearance resembled a steam locomotive. The electric locomotive was powered by electric current from the track rails, one of which was connected to the positive and the other to the negative pole of the generator. In 1883, T. A. Edison, together with S. D. Field, built a more advanced electric locomotive ("The Judge"), exhibited at an exhibition in Chicago and later in Louisville.
By 1883, the work of the American engineer L. Daft, who created the first mainline electric locomotive ("Atreg") for standard gauge, designed for the Saratoga-McGregor railway, belongs. In 1885, Daft built an improved electric locomotive for the New York Trestle Railroad. The locomotive, named "Benjamin Franklin", weighed 10 tons, had a length of more than 4 m and was equipped with four driving wheels. An electric current of 250 V was supplied along the third rail to a 125 hp motor. s, which could pull an eight-car train at a speed of 10 miles per hour (16 km / h).
In 1884, the Swiss engineer R. Tory built an experimental gear railway, connecting the hotel located on a mountain slope with the town of Terry (near Montreux on Lake Geneva). The locomotive had four driving wheels and moved along a very steep slope (1:33). Its capacity was small and allowed to transport four passengers at the same time. On the descent, during braking, the motor worked as a generator, returning electrical energy to the network.
For a number of years, engineering thought has worked tirelessly to improve the technique of supplying current to an electric locomotive.
In 1884, in Cleveland, Bentley and Knight built a streetcar with an underground wire. A similar system was introduced in 1889 in Budapest. This method of power supply turned out to be inconvenient to use, as the chute quickly became dirty.
At the end of 1884, in Kansas City (USA), Henry tested a system with copper overhead wires, one of which was direct, the other was reverse.
By 1885, the Belgian specialist Van Depoule built the first tram with one overhead working wire in Toronto (Canada). In his scheme, the running rails served as a return wire. Poles with consoles were built along the line, to which insulators with a working wire were attached. Contact with the working wire was carried out with the help of a metal roller mounted on a tram rod, which “rolled” along the wire during movement.
This suspension system proved to be very rational, after further improvement it was adopted in many other countries and soon became widespread. By 1890, about 2,500 km of tram-type electric roads were in operation in the USA, and by 1897, 25,000 km. The electric tram began to replace the old types of urban transport.
In 1890, an overhead wire appeared for the first time in Europe on a tram line in Halle (Prussia). Since 1893, electric railways in Europe have been developing at an accelerated pace, as a result of which by 1900 their length had reached 10 thousand km.
In 1890, electric traction was applied to the built underground London road. An electric current of 500 V was supplied to the electric motor using the third rail. This system proved to be very successful for self-tracking roads and began to spread rapidly in other countries. One of its advantages is the possibility of electrifying roads with a very high consumption of electricity, which included subways and mainline railways.
In 1896, electric traction using a current-carrying third rail was first introduced on the Baltimore-Ojai section of the railroad. Electrification affected a 7 km long section of the road on the approach to Baltimore. A 2.5-kilometer tunnel was laid on this section of the track, prompting the builders to electrify it. Electric locomotives operating in this section received electrical energy from the third rail at a voltage of 600 V.
The first electrified railways were short in length. The construction of long-distance railways ran into difficulties associated with the large energy losses that are caused by the transmission of direct current over long distances. With the advent of AC transformers in the 1980s, which made it possible to transmit current over long distances, they were introduced into the power supply circuits of railway lines.
With the introduction of transformers in the power supply system, the so-called "three-phase-direct current system", or, in other words, "three-phase power transmission direct current system", was formed. The central electric station produced a three-phase current. It was transformed into high voltage (from 5 to 15 thousand V, and in the 20s - up to 120 thousand V), which was supplied to the corresponding sections of the line. Each of them had its own step-down substation, from which the alternating current was directed to an alternating current electric motor mounted on one shaft with a direct current generator. The working wire was powered by electricity from it. In 1898, a railway of considerable length with an independent track and a three-phase current system was built in Switzerland and connected Freiburg-Murten-Ins. It was followed by the electrification of a number of other sections of railways and subways.
By 1905, electric traction completely replaced steam on underground roads.
Shukhardin S. "Technology in its historical development"
With the development of industry and Agriculture countries, the amount of goods that needs to be transported from one region of the country to another increases, and this imposes requirements on railway transport to increase the carrying and throughput capacity of railways. In our country, more than half of the total cargo turnover is mastered by electric traction.
There were no electric railways in Tsarist Russia. The electrification of the main highways was planned in the first years of Soviet power during the organization of the country's planned economy.
In the GOELRO plan developed in 1920, attention was paid to increasing the carrying and throughput capacity of railways by transferring them to electric traction. In 1926, the Baku-Surakhani line was electrified with a length of 19 km at a voltage in the contact network of 1200 V DC. In 1929, the suburban section Moscow - Mytishchi, 17.7 km long, with a voltage of 1500 V in the contact network, was switched to electric traction. current. After that, the electrification of some of the most severe in terms of climatic conditions, the most traffic-intensive sections and lines with a heavy profile, began.
By the beginning of World War II, the most difficult sections in the Caucasus, the Urals, Ukraine, Siberia, the Arctic and the suburbs of Moscow with a total length of about 1900 km were transferred. During the war, lines were electrified in the Urals, in the suburbs of Moscow and Kuibyshev with a total length of about 500 km.
After the war, sections of electrified railways in the western part of the country, located on the territory temporarily occupied by the enemy, had to be restored. In addition, it was necessary to transfer new heavy sections of railways to electric traction. Suburban sections, previously electrified at a voltage of 1500 V in the contact wire, were transferred to a voltage of 3000 V. Starting from 1950, from the electrification of individual sections, they switched to transferring entire freight-intensive directions to electric traction and work began on the lines Moscow-Irkutsk, Moscow -Kharkov, etc.
The increase in the flow of national economic goods and the growth of passenger traffic require more powerful locomotives and an increase in the number of trains. At a voltage in the contact network of 3000 V, the currents consumed by powerful electric locomotives, with a significant amount of them in the power supply zone from traction substations, caused large energy losses. To reduce losses, it is necessary to put traction substations closer to one another and increase the cross section of the wires of the contact network, but this increases the cost of the power supply system. It is possible to reduce energy losses by reducing the currents passing through the wires of the contact network, and in order for the power to remain the same, it is necessary to increase the voltage. This principle is used in the electric traction system of alternating single-phase current of industrial frequency of 50 Hz at a voltage in the contact network of 25 kV.
The currents consumed by the electric rolling stock (electric locomotives and electric trains) are much less than with a direct current system, which makes it possible to reduce the cross section of the wires of the contact network and increase the distances between traction substations. This system in our country began to be explored even before the Great Patriotic War. Then, during the war, research had to be stopped. In 1955-1956. according to the results of post-war developments, the experimental section of the Necklace-Pavelets of the Moscow road was electrified using this system. In the future, this system began to be widely introduced on the railways of our country, along with a direct current electric traction system. By the beginning of 1977, electrified lines in the USSR stretched for a distance of about 40 thousand km, which is 28% of the length of all railways in the country. Of these, about 25 thousand km are on direct current and 15 thousand km are on alternating current.
Railways from Moscow to Karymskaya with a length of over 6300 km, from Leningrad to Yerevan - about 3.5 thousand km, Moscow-Sverdlovsk - over 2 thousand km, Moscow-Voronezh-Rostov, Moscow-Kyiv-Chop, lines connecting the Donbass with the Volga region and with the western part of Ukraine, etc. In addition, the suburban traffic of all large industrial and cultural centers has been switched to electric traction.
In terms of the rate of electrification, the length of lines, the volume of traffic and cargo turnover, our country has left far behind all the countries of the world.
intensive railway electrification due to its great technical and economic advantages. Compared to a steam locomotive or with the same weight and dimensions, it can have significantly more power, since it does not have a primary engine (steam engine or diesel engine). Therefore, the electric locomotive provides work with trains at much higher speeds and, consequently, increases the throughput and carrying capacity of railways. Using the control of several electric locomotives from one post (a system of many units) allows you to increase these figures to an even greater extent. Higher travel speeds provide faster delivery of goods and passengers to their destination and bring additional economic benefits to the national economy.
Electric traction has a higher efficiency than diesel traction and especially steam traction. The average operational efficiency of steam traction is 3-4%, diesel locomotive - about 21% (with 30% use of diesel power), and electric traction - about 24%.
When an electric locomotive is powered by old thermal power plants, the efficiency of electric traction is 16-19% (with the efficiency of the electric locomotive itself being about 85%). Such a low efficiency of the system with a high efficiency of an electric locomotive is due to large energy losses in furnaces, boilers and turbines of power plants, the efficiency of which is 25-26%.
Modern power plants with powerful and economical units operate with an efficiency of up to 40%, and an efficiency of up to 40%. electric traction when receiving energy from them is 25-30%. The most economical operation of electric locomotives and electric trains is when the line is powered by a hydroelectric power station. At the same time, the efficiency of electric traction is 60-62%.
It should be noted that steam locomotives and diesel locomotives operate on expensive and high-calorie fuel. Thermal power plants can operate on lower grades of fuel - brown coal, peat, shale, and also use natural gas. The efficiency of electric traction also increases when the sections are powered by nuclear power plants.
Electric locomotives are more reliable in operation, require lower costs for equipment inspections and repairs, and allow increasing labor productivity by 16-17% compared to diesel traction.
Only electric traction has the properties to process the mechanical energy stored in the train into electrical energy and transfer it during regenerative braking to the contact network for use by other electric locomotives or motor cars operating in the traction mode during this period. In the absence of consumers, energy can be transferred to the power system. Due to energy recovery, it is possible to obtain a large economic effect. Thus, in 1976, about 1.7 billion kWh of electricity was returned to the grid due to recuperation. Regenerative braking makes it possible to increase the level of train traffic safety, reduce the wear of brake pads and wheel rims.
All this makes it possible to reduce the cost of transportation and make the process of transporting goods more efficient.
Due to the technical reconstruction of traction in railway transport, approximately 1.7 billion tons of fuel were saved, and operating costs decreased by 28 billion rubles. If we assume that until now steam locomotives would work on our highways, then, for example, in 1974 it would be necessary to use up one third of the coal mined in the country in their furnaces.
Electrification of Russian Railways contributes to the progress of the national economy of the surrounding areas, since industrial enterprises, collective farms, state farms receive power from traction substations and inefficient, uneconomical local diesel power stations are closed. Every year, over 17 billion kWh of energy goes through traction substations to supply non-traction consumers.
With electric traction, labor productivity increases. If with diesel traction labor productivity increases by 2.5 times compared with steam, then with electric traction it increases by 3 times. The cost of transportation on electrified lines is 10-15% lower than with diesel traction.
The power supply system of an electrified railway consists of the external part of the power supply system, which includes devices for the generation, distribution and transmission of electrical energy to traction substations (exclusively);
The traction part of the power supply system, consisting of traction substations of linear devices and a traction network. The traction network, in turn, consists of a contact network, a rail track, supply and suction lines (feeders), as well as other wires and devices connected along the length of the line and contact suspension directly or through special autotransformers.
The main consumer of electrical energy in the traction network is the locomotive. Due to the random location of trains, random combinations of loads are inevitable (for example, the passage of trains with a minimum interval between trains), which can significantly affect the operating modes of the traction power supply system.
Along with this, trains moving away from the traction substation are powered by electric energy at a lower voltage, which affects the speed of the train and, as a result, the throughput of the section.
In addition to the traction motors that drive the train, locomotives have auxiliary machines that perform various functions. The performance of these machines is also related to the voltage level on their clamps. It follows that in traction power supply systems it is very important to maintain a given voltage level at any point of the traction network.
The power supply of the electrified section of the railway is carried out from the power system of a particular region. A schematic diagram of the power supply of an electrified railway is shown in fig. 1.3.
The external power supply system (I) includes an electrical station 1, a transformer substation 2, a power line 3. The traction power supply system (II) contains a traction substation 4, supply feeders 5, a suction feeder 6, a contact network 7 and a traction rail 9 (see Fig. Fig. 1.3), as well as linear devices.
Railways are supplied with electricity via lines 35, 110, 220 kV, 50 Hz. The traction power supply system can be either direct or alternating current.
Rice. 1.3. Schematic diagram of the power supply of the electrified railway: 1 - district power station; 2 - boost transformer substation; 3 - three-phase power line; 4 - traction substation; 5 - supply line (feeder); 6 - suction line (feeder); 7 - contact network; 8 - electric locomotive; 9 - rails
On the railways of Russia, a direct current power supply system with a voltage in the contact network of 3 kV and an alternating current power supply system with a voltage in the contact network of 25 kV and 2 × 25 kV, with a frequency of 50 Hz, have become widespread.
As of January 1, 2005, the length of electrified railways in Russia amounted to 42.6 thousand km.
3 kV direct current traction power supply system
The power supply circuit of the electrified section of the DC railway is shown in fig. 1.4.
In most cases, the traction network is powered from 110 (220) kV buses through a step-down transformer, which provides voltage reduction to 10 kV. A converter is connected to the 10 kV buses, which consists of a traction transformer and a rectifier. The latter provides the conversion of alternating current into constant voltage on tires 3.3 kV. The contact network is connected to the "plus bus", and the rails - to the "minus bus".
Rice. 1.4. Schematic diagram of the power supply of an electrified section of a DC railway with a voltage in the contact network of 3 kV
The fundamental feature of the DC traction power supply system is the electrical connection of the traction motor with the contact network, i.e. there is a contact current collection system. Traction motors for DC electric locomotives and electric trains are designed for a rated voltage of 1.5 kV. The pair-wise series connection of such motors makes it possible to have a voltage of 3 kV in the traction network.
The advantage of a DC system is determined by the quality of a serial DC motor, the characteristic of which to a greater extent meets the requirements for traction motors.
The disadvantages of the DC traction power supply system are as follows:
Due to the low voltage in the traction network, current loads and large losses of electricity (the total coefficient of performance (COP) of the DC electric traction system is estimated at 22%);
At high current loads, the distance between traction substations is 20 km or less, which determines the high cost of the power supply system and high operating costs;
Large current loads determine the need to have a contact suspension of a larger cross section, which causes a significant overrun of scarce non-ferrous metals, as well as an increase in mechanical loads on the contact network supports;
The DC electric traction system is characterized by large losses of electrical energy in the starting rheostats of electric locomotives during acceleration (for suburban traffic, they amount to approximately 12% of the total electrical energy consumption for train traction);
With direct current electric traction, there is intense corrosion of underground metal structures, including contact network supports;
The six-pulse rectifiers used until recently at traction substations had a low power factor (0.88 ÷ 0.92) and, due to the non-sinusoidal curve of the consumed current, caused a deterioration in the quality of electrical energy (especially on 10 kV buses).
On DC roads, a distinction is made between centralized and distributed power supply schemes. The main difference between these schemes lies in the number of rectifier units in substations and the methods of power reservation. With a centralized power supply scheme for units at a substation, there must be at least two. In the case of distributed power, all substations are single-unit, and the distance between traction substations is reduced.
There is a requirement that in cases of failure of one unit, normal movement sizes are provided. In the first scheme, additional (reserve) units are used for redundancy, and in the second, a deliberate rejection of substation equipment redundancy by nodes and a transition to the entire substation redundancy.
As of January 1, 2005, the length of electric railways electrified by a direct current system with a voltage in the traction network of 3 kV amounted to 18.6 thousand km.
Traction power supply system of single-phase alternating current with a voltage of 25 kV, a frequency of 50 Hz
On railways electrified on alternating current, the most widespread power supply system is 25 kV, 50 Hz. The schematic diagram of the power supply of the electrified section is shown in fig. 1.5.
Rice. 1.5. Schematic diagram of the power supply of an electrified section of an alternating current railway with a voltage in the contact network of 25 kV, a frequency of 50 Hz
The traction network is powered from 110 (220) kV buses through a step-down (traction) transformer.
It has three windings:
I - high voltage winding 110 (220) kV;
II - winding of low (medium) voltage 27.5 kV for powering the contact network;
III - medium (low) voltage winding 35, 10 kV for supplying non-traction consumers.
Contact network feeders are connected to the 27.5 kV buses. In this case, phases A and B feed different arms of the traction substation. To separate the phases on the contact network, a neutral insert is arranged. Phase C is connected to the rails.
The fundamental feature of the AC traction power supply system - the electromagnetic connection of the traction motor with the contact network - is provided by means of an electric locomotive transformer.
System advantages:
Independent voltage modes are established in the contact network and on the traction motor while maintaining the DC traction motor;
The voltage in the contact network has been increased to 25 kV AC. As a result, the load current decreases at the same transmitted power; voltage and power losses are reduced;
The distance between traction substations has been increased and their number has been reduced (two to three times);
Reduced construction time and increased the rate of electrification;
Reduced consumption of non-ferrous metals.
Disadvantages of AC traction power supply system:
Asymmetric operation of three-phase transformers (for a two-arm load) and, as a result, deterioration in the quality of electrical energy and a significant decrease in their available power. Note that the available power of a transformer operating in an unbalanced mode is understood as the power corresponding to the positive sequence current at such a load when the current in one of the phases of the transformer takes on the nominal value;
The non-sinusoidality of the system of consumed currents and also the deterioration of the quality of electrical energy in the supply system of the power supply (the curve of the current consumed by electric locomotives with a two-pulse rectifier installed on them contains negative higher harmonics 3, 5, 7 with a large numerical value);
Low power factor of AC electric locomotives. The efficiency of the electric traction system as a whole is estimated at 26%;
AC traction network is a source of electromagnetic influence on adjacent devices, including communication lines, which determines the need for special measures aimed at reducing electromagnetic influence;
The presence of circulating currents with a two-way power supply circuit of an alternating current traction network, and, consequently, additional large losses of electrical energy.
As of January 1, 2005, the length of electric railways electrified by an alternating current system with a voltage in the traction network of 25 kV, a frequency of 50 Hz, amounted to 24.0 thousand km as of January 1, 2005.
Scheme of external power supply of traction substations for direct and alternating current electric traction systems
Power schemes for electrified railways from the power system are very diverse. They depend to a greater extent on the applied electric traction system, as well as on the configuration of the power system itself.
Consider the power supply circuits for electric traction systems of direct (Fig. 1.6) and alternating (Fig. 1.7) current.
Typically, a 50 Hz transmission line is powered by the power grid and is located along the railroad.
The voltage of the electric traction system is understood as the nominal voltage for which the electric rolling stock (EPS) is manufactured. It is also the nominal voltage in the contact network, the voltage on the substation buses is usually taken 10% higher than this value.
On fig. 1.6 and 1.7 are marked: 1 - power system; 2 - power line; 3 - traction substations (with rectifiers, DC substations and transformer substations - AC); 4 - contact network; 5 - rails; 6 - electric locomotive.
Rice. 1.6. Schematic diagram of a DC railroad power supply
Rice. 1.7. AC railroad power circuit diagram
Electrified railways belong to the consumers of the first category. For such consumers, power supply is provided from two independent sources of electricity. These are considered separate district substations, different bus sections of the same substation - district or traction. Therefore, the power supply scheme of traction substations from the power system should be such that the failure of one of the district substations or transmission lines could not cause the failure of more than one traction substation. This can be achieved by choosing a rational power supply scheme for traction substations from the power system.
Schemes for connecting traction substations to linespower transmission
The power supply circuit of traction substations from power lines is shown in fig. 1.8.
Fig 1.8. Scheme of two-way power supply of traction substations from a double-circuit power line
In the general case, the power supply circuit of traction substations depends on the configuration of the district network, the power reserve of power plants and substations, the possibility of their expansion, etc. In all cases, for greater reliability, they tend to have a two-way power supply circuit for traction substations (see Fig. 1.8). On fig. 1.8. marked: 1 - reference traction substation (at least three inputs of high-voltage lines). It is equipped with a complex of high-voltage switching devices and automatic damage protection devices; 2 - intermediate soldering substation. High-voltage switches are not installed, thereby reducing the cost of the power supply system; 3 - intermediate transit substation, sectioning of high-voltage lines for repair or shutdown in case of damage is provided.
Ensuring the reliability of the power supply system is achieved by using a double-circuit high voltage line, providing two-way power supply to each power transmission line network, sectioning power lines at transit substations, and having high-speed automatic protection at basic, transit traction and district substations.
Ensuring the efficiency of the power supply system is achieved by reducing high-voltage equipment (switches) at the expense of intermediate substations that do not have such switches. In case of damage at these substations, the high-speed protection switches off the lines at the reference substations, and during a dead time - at the intermediate ones. Intact substations are switched on by the automatic reclosing system.
When powered from a single-circuit transmission line, the connection of substations on branch lines is not allowed. All substations are included in the section of the line, and at each substation the intermediate transmission lines are sectioned off by a switch.
Features of single-phase current traction network power supply circuitsindustrial frequency
On single-phase alternating current roads, the traction network is powered from a three-phase electric power transmission line through transformers, the windings of which are connected in one or another circuit.
On domestic railways, three-phase three-winding transformers are mainly used, switched on according to the “star-star-triangle” scheme, of the TDTNGE type (three-phase, oil, with forced cooling - blast, three-winding, with voltage regulation under load, lightning-resistant, for electric traction) power 20, 31.5 and 40.5 MV?A. Primary voltage - 110 or 220 kV, secondary for traction - 27.5 kV, for regional consumers - 38.5 and 11 kV.
To power only the traction load, three-phase two-winding transformers of the TDG and TDNG types are used with a star-delta winding connection scheme (-11). The power of these transformers is the same as that of three-winding ones. The connection of the traction winding with a "triangle" allows you to get a flatter external characteristic. One vertex of the "triangle" is attached to the rails, and the other two - to different sections of the contact network.
The power supply circuit of a single-phase alternating current traction network from a three-phase transformer with a star-delta winding connection is shown in fig. 1.9.
When powering the traction load from three phases, the sections of the traction network to the left and right of the substation must be powered from different phases. Therefore, they have voltages out of phase with each other.
Rice. 1.9. Scheme of power supply of a single-phase alternating current traction network from a three-phase transformer with a star-delta winding connection
The currents in the phases can be obtained directly from the Kirchhoff equations. If at the considered moment of time the load is l to the left of the substation and n to the right (see Fig. 1.9), then we can write:
Ac \u003d ba + l; (1.1)
Ba = cb + n; (1.2)
Cb \u003d ac - l - p; (1.3)
Ac + ba + cb = 0. (1.4)
Equation (1.4) implies:
Ba = - ac - cb. (1.5)
We substitute expression (1.5) into equation (1.1):
Ac \u003d - ac - cb + l. (1.6)
Substituting formula (1.3) into expression (1.6), we obtain:
Ac \u003d - ac - ac + l + p + l;
3ac \u003d 2 l + n;
Ac = l + n. (1.7)
Substituting formula (1.7) into expression (1.3), we obtain:
Cb \u003d l + p - l - p;
Cb = - l - p. (1.8)
Substituting formula (1.8) into expression (1.2) we get:
Cb \u003d - l - n + n;
Ba = - l + n. (1.9)
The current in the phases of the secondary "triangle" and, accordingly, in the phases of the primary winding can also be found by building a vector diagram.
To construct a vector diagram, it is assumed that the currents of the feeder zones l and n, which mean the total currents of the feeders, departing from the substation to the left and right, respectively, are distributed between the secondary windings of the transformer. In other words, you need to determine the share of participation secondary winding transformer in the supply of both feeder zones.
When the transformer windings are connected according to the scheme and there are no zero-sequence currents in the closed “triangle” circuit, each phase can be considered independently of the other, i.e., as a single-phase transformer. In this case, the distribution of loads on the secondary side between the phases is determined only by the ratio of the winding resistance values. The left feeder zone with current l is powered by voltage U ac . This voltage is generated both in the “ah” windings and in the “bu” and “cz” windings. The resistance of the "ah" windings is half the resistance of the other two windings connected in series. Therefore, the current l is divided between these voltage-generating windings ac in a ratio of 2:1. The current is divided in the same way.
Let's build a vector diagram to determine the phase currents of a three-phase transformer (Fig. 1.10).
Rice. 1.10. Vector diagram for determining the phase currents of a three-phase transformer
Let us depict the voltage and current vectors I l, I p on the diagram. The current in the “ah” windings, based on the foregoing, should be equal to the sum of l and p. Putting on the vector I l a value equal to its length, on the vector I p of its length, we find ac as the sum of these parts. The current in phase A of the "star" of the primary winding (if we take the transformation ratio equal to one, and the no-load current equal to zero) will be equal to the current a.
Similarly, the current in the "cz" winding is composed of n and - l. Adding them, we get the current c. Accordingly c = C .
The load in the “by” winding is made up of the sum - l and n. By adding the vectors, we get the load of the third least loaded phase b = B. Note that the least loaded phase is the “triangle” phase that is not directly connected to the rails.
On the diagram in fig. 1.10 shows the phase shift angles A, B, C between current I A, I B, I C and voltage U A, U B, U C. Note that A\u003e L, and C< П, т. е. углы сдвига А и С для двух наиболее загруженных фаз оказываются разными (даже для Л = П). У «опережающей» (по ходу вращения векторов) С угол меньше, чем у «отстающей» фазы А. Это существенно влияет на потери напряжения в трансформаторе.
To ensure uniform loading of the phases of power transmission lines, they are alternated when connected to traction substations.
Schemes for connecting a group of traction substations to a power line
The requirements for the connection scheme are as follows:
Ensuring the possibility of parallel operation on the contact network of adjacent traction substations;
Creation of a uniform loading of the power line.
If the power transmission line is powered by one-way, then a cycle of three substations with different phase sequence ensures their uniform load in the area between the source of electrical energy and the first substation (Fig. 1.11). The power plant generators will operate in normal symmetrical load mode. Loss of voltage power transmission lines are reduced due to a decrease in uneven load.
Consider the schemes for connecting traction substations to power lines (see Fig. 1.11).
Substation No. 1. In this case, the terminal of the transformer " A t"Connects to phase A, and the other two -" Vt "and" C t "- to phases B and C, respectively. With this connection, the substation is designated type I. Let's build a vector diagram for this substation (Fig. 1.12).
Lagging phase ac > a. Therefore, the current I ac is shifted by the current I b of the neighboring arm in the direction of lagging. The reactive power consumption increases (in the lagging phase), which leads to a decrease in the voltage in it.
advance phase cb< b . Следовательно, ток I a сдвигает вектор тока I cb в сторону опережения. Потребление реактивной мощности снижается, напряжение увеличивается.
It follows from the foregoing that of the three phases, one is less loaded - the middle one - B.
Substation No. 2. The terminal of the transformer "Vt" will not be connected to the phase of the same name, but to phase C, which will be the actual phase. All feeder zones will receive power from points "a" and "b", but we are no longer free to choose the phase for power after we have chosen the power scheme from the first traction substation.
Let's build a vector diagram (Fig. 1.13). At the second substation, the phase sequence has changed. If at the first substation it was ABC (type I substation), then at the second it became DIA (type II substation). Now the less loaded phase will be phase C.
Substation No. 3. Power supply of the third zone from substation No. 2 is possible only from point "b" (see Fig. 1.11). From substation No. 3, this zone must also be powered from point “b”. Therefore, all odd zones will receive power from points "b" and all even ones - from points "a".
Let's build a vector diagram (Fig. 1.14). The voltage between the contact wires and the rails will be positive in even sections, and negative in odd sections, that is, either in phase with the voltage of one of the phases of the power transmission line, or opposite to it. For substation No. 3, phase A turns out to be the least loaded phase. The sequence of phases will be CAB (type III substation).
Rice. 1.12. Vector diagram of voltages and currents for substation No. 1
Rice. 1.13. Vector diagram of voltages and currents for substation No. 2
Rice. 1.14. Vector diagram of voltages and currents for substation No. 3
The order of alternation of the least loaded phases of the power transmission line will be determined by the number of substations on the site and the power supply scheme of the traction network.
With two-way power transmission lines, cycles that are multiples of three are used (Fig. 1.15).
Rice. 1.15. Connection to power lines of traction substations different types with two-way supply
Unfortunately, connecting a group of traction substations to a power line using phase sequence does not solve the whole problem of current and voltage asymmetry. These issues will be considered separately.
Three-wire traction power supply systemalternating current
This system is a kind of power frequency alternating current system, since the locomotive in this case remains the same. As an example, consider a 2 × 25 kV 50 Hz AC traction power supply system.
The power supply scheme of the electrified section of the railway using the 2 × 25 kV AC traction power supply system is shown in fig. 1.16.
Fig.1.16. The power supply scheme of the electrified section of the railway according to the traction power supply system of alternating current 2 × 25 kV:
1 - step-down transformers of substation No. 1 and 2 (single-phase) 220/25 kV; 2 - linear autotransformers 50/25 kV with a power of 16 mV? A, installed between substations after 10 - 20 km; 3 - connection of rails at the midpoint of a step-down transformer and a linear autotransformer (LAT); 4 - power flow at U = 50 kV; 5 - at U = 25 kV; 6 - electric locomotive
The distance between substations is 60 - 80 km.
The advantages of the system are as follows:
By transferring power to the LAT at more than high voltage(50 kV) power and voltage losses are reduced in the traction network;
The shielding action of the 50 kV supply wire makes it possible to reduce the influence of the contact network on adjacent lines.
The named advantages of the system under consideration determine its application on railways with high cargo density and high-speed passenger traffic.
The disadvantages of the system include:
Rise in the cost of electrification due to the installed capacity of LAT;
Complication of maintenance of the contact network;
Difficulty in voltage regulation.
For the first time, a three-wire AC traction power supply system was used in Japan in 1971. In the Commonwealth countries in 1979, the first section of the Vyazma - Orsha of the Belarusian Railway was installed.
At present, more than 2,000 km have been electrified using this system on the Moscow, Gorky and former Baikal-Amur railways.
The provided power supply system is considered in more detail in the works.
Contact network power supply schemes
Depending on the number of supply paths, the power supply circuits of the contact network can be single- and multi-path. In this case, it is possible to use both one-sided and two-sided power supply.
On single-track sections, schemes of one-way separate, console and counter-console power supply have become widespread. It is also used for two-way power supply.
On double-track sections - schemes of separate, nodal, counter-console, counter-ring and parallel supply.
The choice of the method of supplying the contact network is associated with specific indicators of its operation - reliability and efficiency. Ensuring reliability is achieved by sectioning the contact network and automating the assembly of circuits, efficiency - by reducing the loss of electrical energy and uniform load of the contact network of individual sections and tracks.
The power supply circuits of the contact network are shown in Fig. 1.17 and 1.18.
Single track section(see fig. 1.17). The contact network is divided into two sections (by an insulating interface or a neutral insert), and each section is fed from the substation through its own feeder. If any section is damaged, only this section is disabled (Fig. 1.17, a). With a cantilever scheme (Fig. 1.17, b), the site is powered by one substation on one side. In case of damage, power is removed from the entire area. With the counter-console scheme (Fig. 1.17, c), the site is powered by one substation on one side. Each section has its own feeder. If one of the substations is switched off, the site is without power.
Fig.1.17. Power supply circuits of the contact network of a single-track section
double track section(see fig. 1.18). A separate power supply circuit (Fig. 1.18, a) provides power to each path independently of each other. In this regard, the total cross section of the contact suspension decreases, which leads to an increase in the loss of electrical energy. At the same time, the reliability of this power supply scheme is higher compared to other schemes. The nodal power scheme (Fig. 1.18, b) is performed using sectioning posts. In this case, the loss of electrical energy is reduced due to the possible increase in the cross section of the catenary. If the contact network is damaged, not the entire inter-substation zone is excluded from operation, but only the damaged area between the substation and the sectioning post.
Fig.1.18. Power supply circuits for the contact network of a double-track section
The console circuit (Fig. 1.18, c) provides power to each path separately from different substations. The disadvantages here are the same as in a similar scheme of a single-track section. The counter-console scheme (Fig. 1.18, d) makes it possible to divide the inter-substation zone into sections that are not electrically connected to each other. Each path is fed by its feeder. When the feeder is disconnected, the section is without voltage. The loss of electrical energy is increasing.
The counter-ring scheme (Fig. 1.18, e) allows you to feed the sections along the ring from two substations, which reduces the loss of electrical energy and increases reliability. The parallel circuit (Fig. 1.18, e) of power supply is most widespread. With this scheme, the contact network is powered by two substations on both sides. Since the contact suspension of both paths is electrically interconnected, its cross section increases, which leads to a decrease in electrical energy losses. At the same time, the parallel power supply circuit is highly reliable compared to other circuits.
On domestic railways, the parallel power supply scheme is adopted as the main one.
The first possibilities of equipping the railway with electric traction were discussed in 1874. Russian specialist F.A. Pirotsky in the indicated period of time carried out the first practical experiments on the railway tracks near Sestroretsk on the possibility of transmitting electrical energy through the use of rails isolated from the ground.
The first attempts to equip electric traction
The work was carried out at a distance of one kilometer. The second rail served as a return wire. The resulting electrical energy was supplied to a small engine. Two years later, after the start of the ongoing work, specialist F.A. Pirotsky publishes an article on the results obtained in one of the technical engineering journals. The end result was that he tested the start-up of trolleys moving with the help of the received electricity along the iron tracks.
First practical application
Werner Siemens, who lives in Germany, has implemented the practical application of electricity on the railway. The Berlin Industrial Exhibition of 1879 exhibited this achievement on its premises in the form of a narrow gauge railway, on which the guests of the exhibition had the honor to pass. The train set consisted of several open-type cars pulled by an electric locomotive. The movement was provided by two motors powered by direct current, the voltage of one hundred and fifty volts was given by an iron strip located in the inter-rail space. One of the running rails served as a return wire.
trial plot
Two years later, in the Berlin suburban part of Lichterfeld, the inventor W. Siemens completed the construction of test railways provided with electric power, and a car equipped with a motor moved along them. The voltage was one hundred and eighty volts and was fed to one running rail - this was, as it were, a return wire.
To eliminate the possible large loss of electrical energy with poor insulation due to the use of wood sleepers in this capacity, engineer Werner Siemens had to change circuit diagram power supply for the electric motor.
First experience of suspended electrification system
The World Exhibition in Paris became the platform where people saw the electric road with the use of an outboard working drive. Such power supply was in the form of an iron tube suspended above the railroad tracks. A longitudinal cut was made in the lower part of the tube. A shuttle moved in the inside of the pipe, which was connected by means of a flexible wire through the existing slot and attached directly to the locomotive surface of the roof, thus transferring current to the electric motor.
A similar tube was suspended side by side, parallel to the first tube, and served as a reverse drive. A similar system was used on the trams created in 1884, which appeared on the German and Austrian territories in the cities of Offenbach, Frankfurt, Vorderbrühl and Mödling. To ensure the tram traffic, a voltage of three hundred and fifty volts was supplied.
The Irish city of Kinresh in the same years became a kind of platform for innovators who used the third rail as a current conductor on tram lines. It was installed using insulators that were parallel to the running rails. Unfortunately, this new scheme did not have a long practical application, since in urban conditions, it was a clear hindrance to pedestrians and horse teams.
The work of a Russian engineer
The most interesting thing is that Fyodor Apollonovich Pirotsky warned about all these circumstances of technical doom for supplying power to an electric motor in one of his works, published in the newspaper edition of St. Petersburg Vedomosti. They directly stated that his offspring in the form of an electric railway is the simplest and cheapest construction. There is no need to incur additional costs for laying the middle rail line, which increases the cost of the project by five percent at once and hinders carriage traffic on city streets. The implementation of his project will not require the purchase of cast-iron poles, which cost a lot of money. Subsequently, foreign inventors heeded such a reasonable warning from a Russian engineer and put everything into practice.
Inventor F.A. Pirotsky was actively engaged in the implementation of his project, realizing that urban and railway transport had no future without electricity. Based on the results of his new research and testing, there will be a two-tier motor car that appeared on the streets of St. Petersburg, moving along the rails. In 1881, this car was exhibited at the Paris exhibition.
The English city of Brighton became a pioneer in the practical implementation of the Russian engineer's project in 1884. The length of the electric railway, where only one rail was powered, was seven miles. As a result, the net profit of one electric car, compared with a horse-drawn carriage, during the working day amounted to four hundred and twenty francs.
Developments of American engineers
On the American continent, too, they did not sit idly by, but were actively engaged in improving the method of current supply on an already created electric locomobile.
American researcher T.A. Edison conducted search work on the improvement of a railway locomotive that consumes electricity as fuel. Over a four-year period of time, until 1884, T.A. Edison managed to create three short track lines. The version of the locomotive created, running on electric current, was more like a locomotive locomotive model. Power was provided by generators. One of the track rails was powered from the negative, the other rail was connected to the positive generator pole. Already in 1883, at the Chicago exhibition, a modern locomotive for that time appeared on one of the sites, consuming electric current, named as “The Judge”. The creation of this electric locomotive version was carried out in close collaboration with another inventor, S.D. Field.
At the same time, the American engineer L. Daft managed to build the first model of the main electric locomotive, named as "Atreg". The locomotive used standard gauge on the railroad tracks from McGregor to Saratoga. Subsequently, L. Daft manages to improve the technical qualities of his own locomotive version, but now it is called “Benjamin Franklin”, its mass is ten tons, its length is four meters. There were four drive wheels. The supply of electric current, whose voltage was two hundred and fifty volts, was carried out through the third rail, which ensured the operation of the motor, whose power reached the level of one hundred and twenty-five horsepower. They were enough for the train to have eight cars, and they followed, driven by an electric locomotive at a speed equal to sixteen kilometers per hour.
Swiss cog road
The Swiss engineer Mr. R. Thorn, in the same 1884, built an experimental railway with gearing. As a result, the village of Tori and the mountain hotel received a transport artery with a steep slope, along which a small electric locomotive with four driving wheels followed. The power parameters were insignificant and allowed only four people to carry passengers. Going down the slope, the braking mode was turned on, and the electric motor became a generator, giving the generated electrical energy to the network.
Electrification in Russia
Project
Designers of all countries worked to improve the existing electric locomotive versions, as well as on the technique of supplying electricity to the locomotive.
Electrification went its own way in the Russian Empire. The project on how to electrify the first domestic railway appeared at the very end of the nineteenth century, in 1898. But to start building the Oranienbaum electrical line from St. Petersburg to Krasnye Gorki was possible only in 1913. It was not possible to implement the existing plans in full due to the outbreak of the First World War. As a result, limited sections of the road became the city tram route. In Strelna, trams still follow the tracks.
In the post-revolutionary period, the young government of the RSFSR initiated the development of the well-known GOELRO plan and approved it in 1921. The electrification of the tracks was to be completed in ten to fifteen years. The length of the new tracks under the project was three thousand five hundred kilometers, covering only a small part of the most important areas.
Beginning of work
The first railways with electric traction appeared in 1926 on the route from Surakhani to Sabunchi and further to the capital of Azerbaijan - Baku. Three years later, electric trains master the suburban route from Moscow-Passenger to Mytishchi along the Northern Railway.
A little more time passed, and in 1932 the Suramsky pass section received electricity. Now on this road the main traffic was provided by electric locomotives. The electric traction system used direct current, the voltage of which reached a value of three thousand volts. In subsequent years, it was widely used on the railways of the Soviet Union. The first days of electric locomotive operation clearly showed their advantage in comparison with locomotive traction. These indicators were productivity and energy efficiency.
By 1941, the length of all routes provided with electrical energy was one thousand eight hundred and sixty-five kilometers.
post-war period
In the first post-war year, electrified lines reached their total length of two thousand twenty-nine kilometers. It should be noted that six hundred and sixty-three kilometers of the road were restored, and in fact, practically rebuilt.
There was an active restoration of the production capacities of the destroyed factories during the war. A new enterprise appears in the city of Novocherkassk, which specializes in the production of electric locomotives. Two years after the war, the Riga enterprise for the production of electric trains began to operate.
We must not forget that in that difficult post-war period, the electrification of railways required significant infusions of monetary allocations. Therefore, the volume of growth of tracks with electricity lagged far behind the planned plans and amounted to only thirteen percent. There were many reasons for this, starting with scarce funding for the work, and ending with the high cost of materials needed to conduct such construction.
50s
In the fifties of the twentieth century, the level of earned value in relation to planned loads was seventy percent.
At the 20th Party Congress, the First Secretary of the Central Committee of the CPSU N.S. Khrushchev severely criticized the entire leadership of the Ministry of Railways. Some officials were removed from their positions.
One of the tasks of the fifth five-year plan was the construction of new power plant facilities that could meet the needs of an electrified railway.
Subsequent master plans being created required forty thousand kilometers of railway lines to be electrified by 1970.
Building up the pace
And again, industrialization helps to achieve an annual development for the construction of railways equipped with electricity in the amount of two thousand kilometers.
By March 1962, victorious reports appeared about the fulfillment of planned loads by one hundred and five percent, which in physical terms was eight thousand four hundred and seventy-three kilometers. All this clearly testified to the previous lag behind the level of desired results.
In the seventies of the twentieth century, mass replacement with semiconductor rectifiers began to replace mercury rectifiers standing at substations. Each new substation being built was equipped with only semiconductor equipment. All this meant that the most powerful and reliable inverter units appeared in the Soviet Union. They made it possible to return excess energy, which was generated by rolling stock during the period of electric braking, to the primary external network.
Safe and quick disconnection of current in a contact wire network has always been difficult and painful, especially during a short circuit.
Finally, powerful switches appeared at the railway substations.
They were installed in pairs in a sequential pattern.
Russian period
With the onset of the twenty-first century, there is a noticeable decrease in the pace of construction of electrified lines of communication in Russian Railways, a year - this is four hundred and fifty kilometers. Sometimes this value dropped to one hundred and fifty kilometers, and sometimes rose to seven hundred kilometers. A significant part of the electrified tracks was transferred to the use of alternating current. Similar modernization was carried out on the Caucasian, October roads and in the Siberian directions.
Sochi 2014
On the eve of the 2014 Winter Olympics, a new electrified railway was built immediately along the route from Adler to Krasnaya Polyana. Today, the Republic of Belarus continues to work on the electrification of railways on its territory.
