How is electricity transmitted and distributed? Production and use of electrical energy.

K category: Electric installation work

Electrical energy production

Electrical energy (electricity) is the most advanced type of energy and is used in all areas and branches of material production. Its advantages include the possibility of transmission over long distances and conversion into other types of energy (mechanical, thermal, chemical, light, etc.).

Electrical energy is generated at special enterprises - power stations that convert other types of energy into electrical energy: chemical, fuel, water, wind, solar, nuclear energy.

The ability to transmit electricity over long distances makes it possible to build power plants near fuel locations or on high-water rivers, which is more economical than transporting large quantities of fuel to power plants located near electricity consumers.

Depending on the type of energy used, power plants are divided into thermal, hydraulic, and nuclear. Power plants using wind energy and solar heat are still low-power sources of electricity that have no industrial significance.

Used in thermal power plants thermal energy, obtained by burning solid fuel (coal, peat, oil shale), liquid (fuel oil) and gaseous ( natural gas, and at metallurgical plants - blast furnace and coke oven gas).

Thermal energy is converted into mechanical energy by the rotation of the turbine, which is converted into electrical energy in a generator connected to the turbine. The generator becomes a source of electricity. Thermal power plants are distinguished by the type of primary engine: steam turbine, steam engine, internal combustion engine, locomobile, gas turbine. In addition, steam turbine power plants are divided into condensing and heating plants. Condensing stations supply consumers only with electrical energy. The exhaust steam goes through a cooling cycle and, turning into condensate, is again supplied to the boiler.

The supply of heat and electricity to consumers is carried out by heating stations called combined heat and power plants (CHP). At these stations, thermal energy is only partially converted into electrical energy, and is mainly spent on supplying industrial enterprises and other consumers located in close proximity to power plants with steam and hot water.

Hydroelectric power plants (HPPs) are built on rivers, which are an inexhaustible source of energy for power plants. They flow from highlands to lowlands and are therefore capable of mechanical work. On mountain rivers construct a hydroelectric power station using natural water pressure. On lowland rivers, pressure is created artificially by the construction of dams, due to the difference in water levels on both sides of the dam. The primary engines in hydroelectric power plants are hydraulic turbines, in which the energy of the water flow is converted into mechanical energy.

Water rotates the impeller of the hydraulic turbine and the generator, while the mechanical energy of the hydraulic turbine is converted into electrical energy generated by the generator. The construction of a hydroelectric power station solves, in addition to the problem of generating electricity, also a complex of other problems of national economic importance - improving the navigation of rivers, irrigation and watering of arid lands, improving water supply to cities and industrial enterprises.

Nuclear power plants(NPP) are classified as thermal steam turbine stations that do not operate on organic fuel, but use as an energy source the heat obtained during the fission of the nuclei of nuclear fuel (fuel) atoms - uranium or plutonium. At nuclear power plants, the role of boiler units is performed by nuclear reactors and steam generators.

Electricity supply to consumers is carried out primarily from electrical networks connecting a number of power plants. Parallel operation of power plants on a common electrical network ensures rational distribution of the load between power plants, the most economical generation of electricity, better use of the installed capacity of the stations, increased reliability of power supply to consumers and the supply of electricity to them with normal quality indicators in frequency and voltage.

The need for unification is caused by the unequal load of power plants. Consumer demand for electricity changes sharply not only during the day, but also during different times of the year. In winter, electricity consumption for lighting increases. In agriculture, electricity is needed in large quantities in the summer for field work and irrigation.

The difference in the degree of load of stations is especially noticeable when the areas of electricity consumption are significantly distant from each other in the direction from east to west, which is explained by the different timing of the hours of morning and evening maximum load. To ensure reliable power supply to consumers and to make fuller use of the power of power plants operating in different modes, they are combined into energy or electrical systems using high-voltage electrical networks.

The set of power plants, power transmission lines and heating networks, as well as receivers of electrical and thermal energy, connected into one by the commonality of the regime and the continuity of the process of production and consumption of electrical and thermal energy, is called an energy system (energy system). An electrical system consisting of substations and power lines of various voltages is part of the power grid.

The power systems of individual areas, in turn, are interconnected for parallel operation and form large systems, for example, the unified energy system (UES) of the European part of the USSR, the integrated systems of Siberia, Kazakhstan, Central Asia and etc.

Combined heat and power plants and factory power plants are usually connected to the electrical network of the nearest power system via generator voltage lines of 6 and 10 kV or higher voltage lines (35 kV and above) through transformer substations. The energy generated by powerful regional power plants is transferred to the power grid to supply consumers via high voltage lines (110 kV and above).

It's no secret that electricity comes into our home from power plants, which are the main sources of electricity. However, there may be hundreds of kilometers between us (consumers) and the station, and through all this long distance the current must somehow be transmitted with maximum efficiency. In this article, we will actually look at how electricity is transmitted at a distance to consumers.

Electricity transportation route

So, as we have already said, the starting point is the power station, which, in fact, generates electricity. Today, the main types of power plants are hydro (hydroelectric power plants), thermal power plants (thermal power plants) and nuclear power plants (nuclear power plants). In addition, there are solar, wind and geothermal electricity. stations.

Next, electricity is transmitted from the source to consumers, who may be located over long distances. To transmit electricity, you need to increase the voltage using step-up transformers (the voltage can be increased up to 1150 kV, depending on the distance).

Why is electricity transmitted at increased voltage? Everything is very simple. Let's remember the formula for electrical power - P=UI, then if you transfer energy to the consumer, then the higher the voltage on the power line, the less current in the wires, with the same power consumption. Thanks to this, it is possible to build power lines with high voltage, reducing the cross-section of the wires, compared to power lines with lower voltage. This means that construction costs will be reduced - the thinner the wires, the cheaper they are.

Accordingly, electricity is transferred from the station to a step-up transformer (if necessary), and after that, with the help of power lines, electricity is transferred to the central distribution substations (central distribution substations). The latter, in turn, are located in cities or close to them. At the central distribution point, the voltage is reduced to 220 or 110 kV, from where the electricity is transmitted to substations.

Next, the voltage is reduced again (to 6-10 kV) and the electrical energy is distributed among transformer points, also called transformer substations. Electricity can be transmitted to transformer points not via power lines, but by an underground cable line, because in urban environments this will be more appropriate. The fact is that the cost of rights-of-way in cities is quite high and it will be more profitable to dig a trench and lay a cable in it than to take up space on the surface.

Electricity is transmitted from transformer points to multi-storey buildings, private sector buildings, garage cooperatives, etc. We draw your attention to the fact that at the transformer substation the voltage is reduced once again, to the usual 0.4 kV (380 volt network).

If we briefly consider the route for transmitting electricity from the source to consumers, it looks like this: power plant (for example, 10 kV) - step-up transformer substation (from 110 to 1150 kV) - power lines - step-down transformer substation - transformer substation (10-0.4 kV) – residential buildings.

This is how electricity is transmitted through wires to our home. As you can see, the scheme for transmitting and distributing electricity to consumers is not too complicated, it all depends on how long the distance is.

You can clearly see how electrical energy enters cities and reaches the residential sector in the picture below:

Experts talk about this issue in more detail:

How electricity moves from source to consumer

What else is important to know?

I would also like to say a few words about the points that intersect with this issue. Firstly, research has been carried out for quite some time on how to transmit electricity wirelessly. There are many ideas, but the most promising solution today is the use of Wi-Fi wireless technology. Scientists from the University of Washington found that this method is quite feasible and began to study the issue in more detail.

Secondly, today AC power lines transmit alternating current, not direct current. This is due to the fact that converting devices, which first rectify the current at the input and then make it variable again at the output, have a fairly high cost, which is not economically feasible. However, still throughput power lines direct current 2 times higher, which also makes us think about how to implement it more profitably.

Generation, transmission and distribution of electricity.

The problem of energy supply in the very near future will become one of the most acute among global problems humanity. More than 60% of energy is generated at thermal power plants (TPPs) using organic fuels (coal, oil products, gas, peat), approximately 18% - at nuclear (NPP) and hydroelectric power plants (HPP), and the remaining 2% - at solar, wind, geothermal and other power plants.

The production of electrical energy in Russia is concentrated mainly at large power plants. Consumers of electrical energy – industry, construction, electrified transport, Agriculture, consumer services are located in cities and rural areas. Electricity consumption centers, as a rule, are located at distances of hundreds and even thousands of kilometers from its sources and are distributed over a large area. In this regard, the problem arises of transporting electricity from stations to consumers. This task is performed Electricity of the net, consisting of power transmission lines (PTL) and substations.

Transfer of electrical energy from power plants to big cities or industrial centers at distances of thousands of kilometers is a complex scientific and technical problem.

To reduce losses due to heating of wires, it is necessary to reduce the current in the transmission line (PTL), and, consequently, increase the voltage. Typically, power transmission lines are built for a voltage of 400–500 kV, and the lines use three-phase current with an alternating frequency of 50 Hz. The figure shows a diagram of the electricity transmission line from the power plant to the consumer. The diagram gives an idea of ​​the use of transformers in the transmission of electricity.

It should be noted that as the voltage in transmission lines increases, energy leakage through the air increases. In wet weather, near the line wires, the so-called corona discharge , which can be detected by a characteristic crackling sound. Coefficient useful action transmission line does not exceed 90%.

Schematic diagram of a high-voltage transmission line. Transformers change voltage at several points along a line. The diagram shows only one of the three wires of the high-voltage line.

Among the AC devices found wide application in technology, occupy a significant place transformers.

Transformer –a device for converting voltage and power of alternating current at a constant frequency.

It was invented by P. N. Yablochkov in 1876. In 1882, the transformer was improved by I.F. Usagin.

Operating principle of transformers, used to increase or decrease AC voltage, based on the phenomenon of electromagnetic induction.

The simplest transformer consists of a closed-shaped core made of soft magnetic material, on which two windings are wound: primary and secondary.

The primary winding is connected to an alternating current source with emf e 1 (t), so a current arises in it J 1 (t), creating an alternating magnetic flux Φ in the transformer core, which circulates through a closed magnetic core practically without dissipation and, therefore, penetrates all turns of the primary and secondary windings.

In mode idle move , that is with the secondary winding circuit open, the current in the primary winding is very small due to the large inductive reactance of the winding. In this mode, the transformer consumes little power.

In mode loads V secondary circuit load resistance R n is turned on, and an alternating current appears in it J 2 (t). Now the total magnetic flux Φ in the core is created by both currents. But according to Lenz’s rule, the magnetic flux Φ 2 created by the current induced in the secondary winding J 2, directed towards the flow Φ 1, generated by current J 1 in the primary winding: Φ = Φ 1 – Φ 2. It follows that the currents J 1 and J 2 change in antiphase, that is, they have phase shift, equal to 180°.

Coefficient k =n 1 /n 2 There is transformation ratio.

At k>1 transformer is called increasing, at k<1 – downward.

The relations written above, strictly speaking, apply only to ideal transformer, in which there is no magnetic flux dissipation and no energy loss due to Joule heat. These losses may be associated with the presence of active resistance of the windings themselves and the occurrence of induced currents ( Foucault's currents) in the core. To reduce Foucault currents Transformer cores are usually made of thin steel sheets insulated from each other. There is another mechanism of energy loss associated with hysteresis phenomena in the core. During cyclic magnetization reversal of ferromagnetic materials, electromagnetic energy losses occur that are directly proportional to the area of ​​the hysteresis loop.

In good modern transformers, energy losses at loads close to the rated ones do not exceed 1–2%, therefore the theory of an ideal transformer is approximately applicable to them.

If we neglect energy losses, then the power P 1 consumed by an ideal transformer from an alternating current source is equal to the power P 2 transmitted to the load.

Ministry of Education and Science of Ukraine

Dokuchaevsky Mining College

Essay

in physics on the topic:

"Receipt, transmission and distribution of energy"

Completed by a student of the ERGO group 23 1/9 Narizhny S.G.

Teacher: Ushkalo I.G.

Dokuchaevsk - 2004

When developing coal shale alluvial, ore and non-metallic deposits, the main type of energy is electrical energy, which enterprises receive from the country's power systems, and in remote areas - from local power plants.

An energy system is a set of power plants, electrical and thermal networks associated with a common mode in the continuous process of production, transformation and distribution of electrical and thermal energy under the general control of this mode. The electrical part of the power system includes the totality of electrical installations of power stations and electrical networks.

Power supply is the provision of electrical energy to consumers, and the power supply system is a set of electrical installations designed for this purpose. Power supply can be external or internal.

TO external power supply include overhead and cable power transmission lines (PTLs) from the outputs of regional substations or branches from power systems to the inputs to the buses of the main step-down substations (MSS) of enterprises.

TO internal power supply include surface and underground substations (stationary and mobile), distribution points of high and low voltage, overhead and cable power lines and power receivers of mining enterprises.

Currently, when designing power supplies for new mining areas and reconstructing old ones, deep input systems with a voltage of 35–220 kV are provided, i.e. High voltage electricity is supplied to consumers, minimizing the number of network links and intermediate transformation stages.

The specific value of the supplied voltage is determined on the basis of technical and economic calculations, which compare the initial construction costs, operating costs, indicators regarding the quality of electricity, and prospects for the further development of the power supply system.

Power supply to mining enterprises must be carried out through at least two power transmission lines, regardless of the voltage value. In normal mode, all supply power lines must be under load and operate separately. It is also possible to use double-circuit overhead power lines on supports designed for increased wind and ice loads (one step higher than the standards established for the given area).

In the external power supply system of mining enterprises, the following voltage values ​​are used: 220, 110, 35, 10 and 6 kV. In the internal power supply system for various needs of the enterprise, the following voltages are used: 6 kV (10 kV) - for stationary electrical energy receivers, mobile transformer substations, machines and mechanisms used in shaft sinking, as well as for high-performance mobile power installations in open-pit mines. A voltage of 10 kV may be used in some cases for stationary installations of coal and shale mines and stationary underground substations of ore and non-metallic mines only with the permission of industry ministries;

· 1140V– for high-performance face machines and mechanisms in underground mine workings;

· 660V– for networks feeding power electrical receivers in underground mines and open-pit mines;

· 330V– for powering networks specified for voltage 660V;

· 380/220V– for networks that supply power and lighting electrical receivers on the surface of mining enterprises with a three- or four-wire system from common transformers;

· 220 or 127V– for powering hand tools and lighting networks in underground mine workings.

To create rational power supply systems, it is necessary to use complete transformer substations, transformers with automatic voltage regulation, separate power supply to consumers in underground mine workings from transformers with split secondary windings or isolation transformers with a transformation ratio equal to unity.

Classification of electrical stations, substations and electrical networks

Electric station is an industrial enterprise (electrical installation) that serves to produce electrical energy, and sometimes simultaneously to generate thermal energy. Electric stations differ from each other in their purpose, the type of current generated, the type of fuel or energy used and the type of primary machines.

Depending on the type of fuel or energy used, thermal power plants (thermal power plants and state district power plants), hydroelectric power plants (hydroelectric power plants), and nuclear power plants (nuclear power plants) are distinguished. Based on the type of primary machines, power plants are divided into stations with steam, hydraulic, gas turbines, nuclear reactors, and internal combustion engines. Stations with steam turbines can be condensing (CPS) and heating (CHP).

Substation – This is an electrical installation used for the transformation and distribution of electricity and consisting of power transformers or other energy converters, high and low voltage switchgear, battery, control devices, protection and auxiliary structures.

Surface substations of mining enterprises can be classified according to two criteria: purpose and design. According to their purpose, they have the following abbreviated names: GPP - the main step-down substation, which receives electricity from the power system or directly from the power plant and distributes this energy to the enterprise's power receivers; The central distribution point is a central distribution point that receives power similar to the GPP and distributes the received energy to electrical receivers of the entire enterprise or a separate part of it. CRP is mainly used in open-pit mining. KTP - complete transformer substations, consisting of one or more transformers, high and low voltage switchgear with protective switching equipment. When installing them outdoors, the letter H (outdoor installation) is added to the designation.

Electrical network call a set of electrical installations for the transmission and distribution of electricity, consisting of substations, switchgears, conductors, overhead and cable power lines operating in a certain territory.

By air line(VL) power transmission is a device for transmitting and distributing electricity through wires located in the open air and attached using insulators and fittings to various types of supports or brackets and racks on engineering structures (bridges, overpasses, etc.). The linear portals of distribution devices are taken as the beginning and end of the overhead line.

Cable line(CL) is a line for transmitting electricity, consisting of one or more cables with connecting, locking and end couplings (terminals) and fasteners.

Independent power supply consumers of electrical energy are called a power source on which the voltage is maintained within the established limits after an emergency mode, when it disappears on other power sources of these consumers.

Electrical networks are carried out by overhead or cable power lines. The main elements of overhead lines are: bare wires, supports, insulators, linear fittings and lightning protection cables. Currently, aluminum and steel-aluminum wires are used. By design, the wires can be single-wire, stranded from one metal, or stranded from two metals, such as aluminum and steel.

The arrangement of wires on supports can be different: on single-circuit lines - in a triangle (Fig. a) or horizontally (Fig. b); on two chain lines - a reverse Christmas tree (Fig. c) or a hexagon in the form of a barrel (Fig. d). Lightning protection cables are installed at the top points of the supports.

With any option, the wires are placed asymmetrically, which leads to unequal values ​​of reactance and conductivity. In order to obtain the same capacitances and inductances of all three phases of power lines in different sections of long power lines, the relative position of the wires relative to each other on the supports is sequentially changed, i.e., the so-called transposition of the wires is used.

The supports are made of wood, steel and reinforced concrete. The main types of supports: anchor and intermediate. The first ones are installed to rigidly fasten wires at the ends of a line or its straight sections, at the intersections of particularly important engineering structures and large bodies of water. The anchor supports must be able to withstand one-sided tension of two wires. Intermediate supports serve to support the wire on straight sections of power lines between adjacent anchor supports. With such supports, the tension of the wires is not transferred to these supports. Wooden supports made from pine and larch are easy to manufacture and cheap. The disadvantage of wooden supports is their short service life. Steel is used for metal supports. They require a lot of metal and need regular painting to protect against corrosion. Reinforced concrete supports are made from unstressed reinforcement, covered with vibro- or centrifuged concrete. Such supports require less metal, are not subject to corrosion, are more durable than wooden ones, and therefore have become widespread in the construction of power lines with voltages up to 750 kV

Overhead line insulators are made of porcelain or tempered glass. These materials have high mechanical and electrical strength and resistance to atmospheric influences. Porcelain insulators are heavier than glass insulators and are less resistant to shock loads. With various damages, porcelain cracks, which is difficult to detect visually, and tempered glass crumbles. There are two types of insulators used on overhead power lines: pin and pendant. The former are used for power lines with voltages up to 35 kV, the latter – for power lines of any voltage. Suspended insulators are assembled into garlands, which are called supporting on intermediate supports, and tension on anchor supports. The number of insulators in a garland depends on the operating voltage of the power transmission line, the degree of atmospheric pollution, the material of the supports and the type of insulators used. For example, on a power line-35 the number of insulators in a garland is three, on a power line-110 - from six to eight, and on a power line-220, 10-14 insulators with a cup diameter from 255 to 350 mm are installed in the supporting garland.

I Introduction
II Electricity production and use
1. Electricity generation
1.1 Generator
2. Electricity use
III Transformers
1. Purpose
2. Classification
3. Device
4. Characteristics
5. Modes
5.1 Idling
5.2 Short circuit mode
5.3 Load mode
IV Electricity transmission
V GOELRO
1. History
2. Results
VI List of references

I. Introduction

Electricity, one of the most important types of energy, plays a huge role in the modern world. It is the core of the economies of states, determining their position in the international arena and level of development. Huge sums of money are invested annually in the development of scientific industries related to electricity.
Electricity is an integral part of everyday life, so it is important to have information about the features of its production and use.

II. Electricity production and use

1. Electricity generation

Electricity generation is the production of electricity by converting it from other types of energy using special technical devices.
To generate electricity use:
An electric generator is an electrical machine in which mechanical work is converted into electrical energy.
A solar battery or photocell is an electronic device that converts the energy of electromagnetic radiation, mainly in the light range, into electrical energy.
Chemical current sources - the conversion of part of the chemical energy into electrical energy through a chemical reaction.
Radioisotope sources of electricity are devices that use the energy released during radioactive decay to heat a coolant or convert it into electricity.
Electricity is generated at power plants: thermal, hydraulic, nuclear, solar, geothermal, wind and others.
Almost all power plants of industrial importance use the following scheme: the energy of the primary energy carrier, using a special device, is first converted into mechanical energy of rotational motion, which is transferred to a special electrical machine - a generator, where electric current is generated.
The main three types of power plants: TPP, HPP, NPP
Thermal power plants (TPPs) play a leading role in the electric power industry of many countries.
Thermal power plants require huge amounts of organic fuel, but its reserves are decreasing, and the cost is constantly increasing due to increasingly complex production conditions and transportation distances. Their fuel utilization rate is quite low (no more than 40%), and the volume of waste that pollutes the environment is large.
Economic, technical, economic and environmental factors do not allow thermal power plants to be considered a promising way to generate electricity.
Hydroelectric power plants (HPP) are the most economical. Their efficiency reaches 93%, and the cost of one kWh is 5 times cheaper than other methods of generating electricity. They use an inexhaustible source of energy, are serviced by a minimum number of workers, and are well regulated. In terms of the size and power of individual hydroelectric power stations and units, our country occupies a leading position in the world.
But the pace of development is hampered by significant costs and construction time due to the remoteness of hydroelectric power station construction sites from large cities, lack of roads, difficult construction conditions, subject to the influence of seasonality of river regimes, large areas of valuable riverine lands are flooded by reservoirs, large reservoirs negatively impact the environmental situation, powerful hydroelectric power stations can only be built in places where appropriate resources are available.
Nuclear power plants (NPPs) operate on the same principle as thermal power plants, i.e., the thermal energy of steam is converted into mechanical energy of rotation of the turbine shaft, which drives the generator, where mechanical energy is converted into electrical energy.
The main advantage of nuclear power plants is the small amount of fuel used (1 kg of enriched uranium replaces 2.5 thousand tons of coal), as a result of which nuclear power plants can be built in any energy-deficient areas. In addition, the reserves of uranium on Earth exceed the reserves of traditional mineral fuel, and during trouble-free operation of nuclear power plants they have little impact on the environment.
The main disadvantage of nuclear power plants is the possibility of accidents with catastrophic consequences, the prevention of which requires serious safety measures. In addition, nuclear power plants are poorly regulated (it takes several weeks to completely shut them down or start them up), and technologies for processing radioactive waste have not been developed.
Nuclear energy has grown into one of the leading sectors of the national economy and continues to develop rapidly, ensuring safety and environmental cleanliness.

1.1 Generator

An electric generator is a device in which non-electrical types of energy (mechanical, chemical, thermal) are converted into electrical energy.
The principle of operation of the generator is based on the phenomenon of electromagnetic induction, when an EMF is induced in a conductor moving in a magnetic field and crossing its magnetic lines of force. Therefore, such a conductor can be considered by us as a source of electrical energy.
The method of obtaining induced EMF, in which the conductor moves in a magnetic field, moving up or down, is very inconvenient for practical use. Therefore, generators use not linear, but rotational movement of the conductor.
The main parts of any generator are: a system of magnets or, most often, electromagnets that create a magnetic field, and a system of conductors that cross this magnetic field.
An alternator is an electrical machine that converts mechanical energy into alternating current electrical energy. Most alternators use a rotating magnetic field.

When the frame rotates, the magnetic flux through it changes, so an emf is induced in it. Since the frame is connected to an external electrical circuit using a current collector (rings and brushes), an electric current arises in the frame and the external circuit.
With uniform rotation of the frame, the angle of rotation changes according to the law:

The magnetic flux through the frame also changes over time, its dependence is determined by the function:

Where S− frame area.
According to Faraday's law of electromagnetic induction, the induced emf arising in the frame is equal to:

where is the amplitude of the induced emf.
Another quantity that characterizes the generator is the current strength, expressed by the formula:

Where i- current strength at any time, I m- current amplitude (maximum modulus current value), φ c- phase shift between current and voltage fluctuations.
The electrical voltage at the generator terminals changes according to a sinusoidal or cosine law:

Almost all generators installed in our power plants are three-phase current generators. Essentially, each such generator is a connection in one electric machine of three alternating current generators, designed in such a way that the emfs induced in them are shifted relative to each other by one third of the period:

2. Electricity use

Power supply for industrial enterprises. Industrial enterprises consume 30-70% of the electricity generated as part of the electrical power system. The significant variation in industrial consumption is determined by the industrial development and climatic conditions of different countries.
Power supply for electrified transport. Rectifier substations of electric transport on direct current (urban, industrial, intercity) and step-down substations of intercity electric transport on alternating current are powered by electricity from the electrical networks of the EPS.
Electricity supply for municipal and household consumers. This group of buildings includes a wide range of buildings located in residential areas of cities and towns. These are residential buildings, administrative buildings, educational and scientific institutions, shops, healthcare buildings, cultural buildings, public catering, etc.

III. Transformers

Transformer - a static electromagnetic device having two or more inductively coupled windings and designed to transform, through electromagnetic induction, one (primary) alternating current system into another (secondary) alternating current system.

Transformer device diagram

1 - primary winding of the transformer
2 - magnetic circuit
3 - secondary winding of the transformer
F- direction of magnetic flux
U 1- voltage on the primary winding
U 2- voltage on the secondary winding

The first transformers with an open magnetic circuit were proposed in 1876 by P.N. Yablochkov, who used them to power an electric “candle”. In 1885, Hungarian scientists M. Dery, O. Blati, K. Tsipernovsky developed single-phase industrial transformers with a closed magnetic circuit. In 1889-1891. M.O. Dolivo-Dobrovolsky proposed a three-phase transformer.

1. Purpose

Transformers are widely used in various fields:
For transmission and distribution of electrical energy
Typically, in power plants, alternating current generators produce electrical energy at a voltage of 6-24 kV, and it is profitable to transmit electricity over long distances at much higher voltages (110, 220, 330, 400, 500, and 750 kV). Therefore, transformers are installed at each power plant to increase the voltage.
The distribution of electrical energy between industrial enterprises, populated areas, in cities and rural areas, as well as within industrial enterprises, is carried out via overhead and cable lines, at voltages of 220, 110, 35, 20, 10 and 6 kV. Consequently, transformers must be installed in all distribution nodes, reducing the voltage to 220, 380 and 660 V.
To provide the required circuit for switching on valves in converter devices and matching the voltage at the output and input of the converter (converter transformers).
For various technological purposes: welding (welding transformers), power supply of electrothermal installations (electric furnace transformers), etc.
For powering various circuits of radio equipment, electronic equipment, communication and automation devices, electrical household appliances, for separating electrical circuits of various elements of these devices, for matching voltage, etc.
To include electrical measuring instruments and some devices (relays, etc.) in high-voltage electrical circuits or in circuits through which large currents pass, in order to expand the measurement limits and ensure electrical safety. (instrument transformers)

2. Classification

Transformer classification:

• By purpose: general power (used in power transmission and distribution lines) and special applications (furnaces, rectifiers, welding, radio transformers).
• By type of cooling: with air (dry transformers) and oil (oil transformers) cooling.
• According to the number of phases on the primary side: single-phase and three-phase.
• According to the shape of the magnetic circuit: rod, armored, toroidal.
• According to the number of windings per phase: two-winding, three-winding, multi-winding (more than three windings).
• According to the winding design: with concentric and alternating (disc) windings.

3. Device

The simplest transformer (single-phase transformer) is a device consisting of a steel core and two windings.

The principle of a single-phase two-winding transformer
The magnetic core is the magnetic system of the transformer, through which the main magnetic flux is closed.
When an alternating voltage is supplied to the primary winding, an emf of the same frequency is induced in the secondary winding. If you connect some electrical receiver to the secondary winding, then an electric current arises in it and a voltage is established at the secondary terminals of the transformer, which is somewhat less than the EMF and depends to some relatively small extent on the load.

Transformer symbol:
a) - transformer with a steel core, b) - transformer with a ferrite core

4. Transformer characteristics

• The rated power of a transformer is the power for which it is designed.
• Rated primary voltage is the voltage for which the primary winding of the transformer is designed.
• Rated secondary voltage - the voltage at the terminals of the secondary winding, resulting from the no-load condition of the transformer and the rated voltage at the terminals of the primary winding.
• Rated currents are determined by the corresponding rated power and voltage values.
• The highest rated voltage of a transformer is the highest of the rated voltages of the transformer windings.
• The lowest rated voltage is the smallest of the rated voltages of the transformer windings.
• Average rated voltage is a rated voltage that is intermediate between the highest and lowest rated voltage of the transformer windings.

5. Modes

5.1 Idling

No-load mode is the operating mode of the transformer in which the secondary winding of the transformer is open and alternating voltage is applied to the terminals of the primary winding.

A current flows in the primary winding of a transformer connected to an alternating current source, resulting in an alternating magnetic flux appearing in the core. Φ , penetrating both windings. Since Φ is the same in both windings of the transformer, then the change Φ leads to the appearance of the same induced emf in each turn of the primary and secondary windings. Instantaneous value of induced emf e in any turn of the windings is the same and is determined by the formula:

where is the amplitude of the EMF in one turn.
The amplitude of the induced emf in the primary and secondary windings will be proportional to the number of turns in the corresponding winding:

Where N 1 And N 2- the number of turns in them.
The voltage drop across the primary winding, like a resistor, is very small compared to ε 1, and therefore for effective voltage values ​​in the primary U 1 and secondary U 2 windings the following expression will be valid:

K- transformation coefficient. At K>1 step-down transformer, and when K<1 - повышающий.

5.2 Short circuit mode

Short circuit mode - a mode when the terminals of the secondary winding are closed by a current conductor with a resistance equal to zero ( Z=0).

A short circuit of a transformer under operating conditions creates an emergency mode, since the secondary current, and therefore the primary one, increases several tens of times compared to the rated one. Therefore, in circuits with transformers, protection is provided that, in the event of a short circuit, automatically turns off the transformer.

It is necessary to distinguish between two short circuit modes:

Emergency mode - when the secondary winding is closed at the rated primary voltage. With such a short circuit, the currents increase by 15¸ 20 times. The winding is deformed and the insulation becomes charred. Iron also burns. This is hard mode. Maximum and gas protection disconnects the transformer from the network in the event of an emergency short circuit.

The experimental short circuit mode is a mode when the secondary winding is short-circuited, and such a reduced voltage is supplied to the primary winding when the rated current flows through the windings - this is U K- short circuit voltage.

In laboratory conditions, a test short circuit of the transformer can be carried out. In this case, the voltage expressed as a percentage U K, at I 1 =I 1nom denote u K and is called the transformer short circuit voltage:

Where U 1nom- rated primary voltage.

This is a characteristic of the transformer indicated in the passport.

5.3 Load mode

Load mode of a transformer - operating mode of a transformer in the presence of currents in at least two of its main windings, each of which is closed to an external circuit, and currents flowing in two or more windings in no-load mode are not taken into account:

If voltage is connected to the primary winding of the transformer U 1, and connect the secondary winding to the load, currents will appear in the windings I 1 And I 2. These currents will create magnetic fluxes Φ 1 And Φ 2, directed towards each other. The total magnetic flux in the magnetic circuit decreases. As a result, the EMF induced by the total flow ε 1 And ε 2 are decreasing. RMS voltage U 1 remains unchanged. Decrease ε 1 causes an increase in current I 1:

With increasing current I 1 flow Φ 1 increases just enough to compensate for the demagnetizing effect of the flow Φ 2. Equilibrium is restored again at almost the same value of the total flow.

IV. Electricity transmission

Transferring electricity from power plants to consumers is one of the most important tasks in the energy sector.
Electricity is transmitted primarily through overhead AC power lines (OLTs), although there is a trend towards increasing use of cable and DC lines.

The need to transmit electricity over a distance is due to the fact that electricity is generated by large power plants with powerful units, and is consumed by relatively low-power electrical receivers distributed over a large area. The trend towards concentration of generating capacity is explained by the fact that with their growth, the relative costs of constructing power plants decrease and the cost of generated electricity decreases.
The placement of powerful power plants is carried out taking into account a number of factors, such as the availability of energy resources, their type, reserves and transportation capabilities, natural conditions, the ability to operate as part of a unified energy system, etc. Often such power plants turn out to be significantly remote from the main centers of electricity consumption. The operation of unified electrical power systems covering vast territories depends on the efficiency of transmitting electricity over distances.
It is necessary to transfer electricity from the places of its production to consumers with minimal losses. The main reason for these losses is the conversion of part of the electricity into the internal energy of the wires, their heating.

According to the Joule-Lenz law, the amount of heat Q, released during time t in the conductor by resistance R when current passes I, equals:

From the formula it follows that to reduce the heating of the wires it is necessary to reduce the current in them and their resistance. To reduce the resistance of the wires, increase their diameter; however, very thick wires hanging between power line supports can break under the influence of gravity, especially during snowfall. In addition, as the thickness of the wires increases, their cost increases, and they are made of a relatively expensive metal - copper. Therefore, a more effective way to minimize energy losses during electricity transmission is to reduce the current in the wires.
Thus, in order to reduce the heating of wires when transmitting electricity over long distances, it is necessary to make the current in them as small as possible.
The current power is equal to the current multiplied by the voltage:

Consequently, to maintain the power transmitted over long distances, it is necessary to increase the voltage by the same amount as the current in the wires was reduced:

It follows from the formula that at constant values ​​of transmitted current power and wire resistance, heating losses in the wires are inversely proportional to the square of the network voltage. Therefore, to transmit electricity over distances of several hundred kilometers, high-voltage power lines (power lines) are used, the voltage between the wires of which is tens and sometimes hundreds of thousands of volts.
With the help of power lines, neighboring power plants are combined into a single network called a power grid. The Unified Energy System of Russia includes a huge number of power plants controlled from a single center and ensures an uninterrupted supply of electricity to consumers.

V. GOELRO

1. History

GOELRO (State Commission for Electrification of Russia) is a body created on February 21, 1920 to develop a project for the electrification of Russia after the October Revolution of 1917.

Over 200 scientists and technicians were involved in the work of the commission. The commission was headed by G.M. Krzhizhanovsky. The Central Committee of the Communist Party and V.I. Lenin personally daily directed the work of the GOELRO commission and determined the main fundamental provisions of the country’s electrification plan.

By the end of 1920, the commission had done a lot of work and prepared the “Electrification Plan of the RSFSR” - a volume of 650 pages of text with maps and diagrams of electrification of areas.
The GOELRO plan, designed for 10-15 years, implemented Lenin’s ideas of electrifying the entire country and creating a large industry.
In the field of the electric power industry, the plan consisted of a program designed for the restoration and reconstruction of the pre-war electric power industry, the construction of 30 regional power stations, and the construction of powerful regional thermal power plants. The power plants were planned to be equipped with boilers and turbines that were large for that time.
One of the main ideas of the plan was the widespread use of the country's enormous hydropower resources. A radical reconstruction based on the electrification of all sectors of the country's national economy and mainly the growth of heavy industry and the rational distribution of industry throughout the country were envisaged.
The implementation of the GOELRO plan began in difficult conditions of the Civil War and economic ruin.

Since 1947, the USSR has ranked 1st in Europe and 2nd in the world in electricity production.

The GOELRO plan played a huge role in the life of our country: without it, it would not have been possible to bring the USSR into the ranks of the most industrially developed countries in the world in such a short time. The implementation of this plan shaped the entire domestic economy and still largely determines it.

The drawing up and implementation of the GOELRO plan became possible solely due to a combination of many objective and subjective factors: the considerable industrial and economic potential of pre-revolutionary Russia, the high level of the Russian scientific and technical school, the concentration in one hand of all economic and political power, its strength and will, as well as the traditional conciliar-communal mentality of the people and their obedient and trusting attitude towards the supreme rulers.
The GOELRO plan and its implementation proved the high efficiency of the state planning system in conditions of strictly centralized government and predetermined the development of this system for many decades.

2. Results

By the end of 1935, the electrical construction program was exceeded several times.

Instead of 30, 40 regional power plants were built, at which, together with other large industrial stations, 6,914 thousand kW of capacity were commissioned (of which 4,540 thousand kW were regional - almost three times more than according to the GOELRO plan).
In 1935, among the regional power plants there were 13 power plants with 100 thousand kW each.

Before the revolution, the capacity of the largest power plant in Russia (1st Moscow) was only 75 thousand kW; there was not a single large hydroelectric power station. By the beginning of 1935, the total installed capacity of hydroelectric power stations reached almost 700 thousand kW.
The largest hydroelectric power station in the world at that time, the Dnieper hydroelectric station, Svirskaya 3rd, Volkhovskaya, etc., were built. At the highest point of its development, the Unified Energy System of the USSR was superior in many respects to the energy systems of developed countries in Europe and America.

Electricity was virtually unknown in villages before the revolution. Large landowners installed small power plants, but their numbers were few.

Electricity began to be used in agriculture: in mills, feed cutters, grain cleaning machines, and sawmills; in industry, and later in everyday life.

List of used literature

Venikov V.A., Long-distance power transmission, M.-L., 1960;
Sovalov S. A., Power transmission modes 400-500 sq. EES, M., 1967;
Bessonov, L.A. Theoretical foundations of electrical engineering. Electric circuits: textbook / L.A. Bessonov. — 10th ed. - M.: Gardariki, 2002.
Electrical engineering: Educational and methodological complex. /AND. M. Kogol, G. P. Dubovitsky, V. N. Borodyanko, V. S. Gun, N. V. Klinachev, V. V. Krymsky, A. Ya. Ergard, V. A. Yakovlev; Edited by N.V. Klinachev. - Chelyabinsk, 2006-2008.
Electrical systems, vol. 3 - Energy transmission by alternating and direct current of high voltage, M., 1972.

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