Summary: Production, transmission and use of electricity. Production, transmission and consumption of electrical energy

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

I Introduction

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

II. Production and use of electricity

1. Power 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 electric machine in which mechanical work converted into electrical energy.
Solar battery or photocell - an electronic device that converts energy electromagnetic radiation, mainly in the light range, into electrical energy.
Chemical current sources - the conversion of part of 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 the coolant or convert it into electricity.
Electricity is generated at power plants: thermal, hydraulic, nuclear, solar, geothermal, wind and others.
Practically at all power plants of industrial importance, the following scheme is used: the energy of the primary energy carrier with the help of a special device is first converted into mechanical energy of rotational motion, which is transferred to a special electrical machine - a generator, where it is generated electricity.
The main three types of power plants: thermal power plants, hydroelectric power plants, nuclear power plants
The leading role in the electric power industry of many countries is played by thermal power plants (TPPs).
Thermal power plants require a huge amount of fossil fuel, while its reserves are declining, and the cost is constantly increasing due to increasingly difficult conditions for extraction and transportation distances. The fuel utilization factor in them is quite low (no more than 40%), and the volume of waste polluting environment, are great.
Economic, techno-economic and environmental factors do not allow considering thermal power plants as a promising way to generate electricity.
Hydropower plants (HPP) are the most economical. Their efficiency reaches 93%, and the cost of one kWh is 5 times cheaper than with other methods of generating electricity. They use an inexhaustible source of energy, are serviced by a minimum number of workers, and are well regulated. Our country occupies a leading position in the world in terms of the size and capacity of individual hydroelectric stations and units.
But the pace of development is constrained by significant costs and construction time, due to the remoteness of HPP construction sites from major cities, lack of roads, difficult construction conditions, affected by the seasonality of the river regime, reservoirs are flooded large areas valuable riverine lands, large reservoirs adversely affect ecological situation, powerful HPPs can only be built in places where the 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 a 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 with 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 stop or turn them on), and technologies for processing radioactive waste have not been developed.
Nuclear power has grown into one of the leading industries National economy and continues to develop rapidly, ensuring safety and environmental friendliness.

1.1 Generator

An electric generator is a device in which non-electrical forms of energy (mechanical, chemical, thermal) are converted into electrical energy.
The principle of operation of the generator is based on the phenomenon electromagnetic induction when in a conductor moving in a magnetic field and crossing its magnetic lines of force, an EMF is induced. Therefore, such a conductor can be considered by us as a source electrical energy.
The method of obtaining an induced emf, in which the conductor moves in a magnetic field, moving up or down, is very inconvenient in its practical use. Therefore, generators use not rectilinear, 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.
Generator alternating current- an electrical machine that converts mechanical energy into electrical energy of alternating current. Most alternators use a rotating magnetic field.

When you rotate the frame, it changes magnetic flux through it, so an EMF is induced in it. Since the frame is connected to an external electrical circuit with the help of 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 EMF of induction that occurs in the frame is:

where is the amplitude of the EMF of induction.
Another value that characterizes the generator is the current strength, expressed by the formula:

where i is the current strength at any given time, I m- the amplitude of the current strength (the maximum value of the current strength in absolute value), φc- phase shift between fluctuations in current and voltage.
The electrical voltage at the generator terminals varies according to a sinusoidal or cosine law:

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

2. Electricity use

Power supply industrial enterprises. Industrial enterprises consume 30-70% of the electricity generated as part of the electric power system. A significant spread of industrial consumption is determined by industrial development and climatic conditions various countries.
Power supply of electrified transport. Rectifier substations for electric transport DC(urban, industrial, intercity) and step-down substations of intercity electric transport on alternating current are powered by electricity from electrical networks EES.
Power supply of household consumers. This group of PE includes a wide range of buildings located in residential areas of cities and towns. This - residential buildings, buildings for administrative and managerial purposes, educational and scientific institutions, shops, buildings for healthcare, cultural and mass purposes, Catering etc.

III. transformers

Transformer - static electromagnetic device, which has two or more inductively coupled windings and designed to convert one (primary) alternating current system into another (secondary) alternating current system by means of electromagnetic induction.

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, the Hungarian scientists M. Deri, O. Blaty, K. Zipernovsky developed single-phase industrial transformers with a closed magnetic circuit. In 1889-1891. M.O. Dolivo-Dobrovolsky proposed a three-phase transformer.

1. Appointment

Transformers are widely used in various fields:
For transmission and distribution of electrical energy
Typically, at power plants, alternating current generators generate 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, at each power plant, transformers are installed that increase the voltage.
Distribution of electrical energy between industrial enterprises, settlements, in cities and rural areas, as well as inside industrial enterprises, it is produced via overhead and cable lines, at a voltage of 220, 110, 35, 20, 10 and 6 kV. Therefore, transformers must be installed in all distribution nodes that reduce the voltage to 220, 380 and 660 V.
To provide the desired circuit for switching on valves in converter devices and to match 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, 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. (measuring transformers)

2. Classification

Transformer classification:

• By appointment: general power (used in power transmission and distribution lines) and special application(furnace, rectifier, 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.
• By the number of windings per phase: two-winding, three-winding, multi-winding (more than three windings).
• According to the design of the windings: with concentric and alternating (disk) windings.

3. Device

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

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

Symbol of the transformer:
a) - a transformer with a steel core, b) - a transformer with a ferrite core

4. Characteristics of the transformer

• The rated power of a transformer is the power for which it is designed.
• Rated primary voltage - the voltage for which the primary winding of the transformer is designed.
• Rated secondary voltage - the voltage at the terminals of the secondary winding, obtained when the transformer is idling and the rated voltage at the terminals of the primary winding.
• Rated currents, determined by the respective nominal values power and voltage.
• The highest rated voltage of the 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 - rated voltage, which is intermediate between the highest and lowest rated voltage of the transformer windings.

5. Modes

5.1 Idling

Idle mode - the mode of operation 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, as a result of which an alternating magnetic flux appears in the core Φ penetrating both windings. Since Φ is the same in both windings of the transformer, the change Φ leads to the appearance of the same induction EMF in each turn of the primary and secondary windings. Instantaneous value of induction 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 induction 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 across a resistor, is very small compared to ε 1, and therefore for effective values voltage in the primary U 1 and secondary U 2 windings, the following expression will be true:

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

5.2 Short circuit mode

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

A short circuit of the 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 nominal one. Therefore, in circuits with transformers, protection is provided that, in the event of a short circuit, automatically turns off the transformer.

Two modes of short circuit must be distinguished:

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

An 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.

Under laboratory conditions, a test short circuit of the transformer can be carried out. In this case, expressed as a percentage, the voltage U K, at I 1 \u003d I 1nom designate u K and is called the short circuit voltage of the transformer:

where U 1nom- rated primary voltage.

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

5.3 Load mode

The load mode of the transformer is the mode of operation of the transformer in the presence of currents in at least two of its main windings, each of which is closed to an external circuit, while currents flowing in two or more windings in idle mode are not taken into account:

If a 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 Φ2 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 decrease. 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 flux Φ2. Equilibrium is restored again at practically the same value of the total flow.

IV. Electricity transmission

The transmission of electricity from the power plant to consumers is one of the most important tasks of the energy industry.
Electricity is transmitted predominantly via AC overhead transmission lines (TL), although there is a trend towards an increasing use of cable lines 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 power consumers distributed over a large area. The trend towards the concentration of generating capacities is explained by the fact that with their growth, the relative costs for the construction of 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 possibilities, natural conditions, the ability to work as part of a single energy system, etc. Often, such power plants turn out to be significantly remote from the main centers of electricity consumption. The operation of unified electric power systems covering vast territories depends on the efficiency of electric power transmission over a distance.
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 the time t in the conductor by resistance R during the passage of current I, equals:

It follows from the formula that in order to reduce the heating of the wires, it is necessary to reduce the current strength 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 action of gravity, especially during snowfall. In addition, with an increase in the thickness of the wires, their cost increases, and they are made of a relatively expensive metal - copper. Therefore, a more effective way to minimize energy losses in the transmission of electricity is to reduce the current strength 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 product of the current strength and voltage:

Therefore, in order to save power transmitted over long distances, it is necessary to increase the voltage by the same amount as the current strength in the wires was reduced:

From the formula it follows that at constant values ​​of the transmitted power of the current and the resistance of the wires, the heating losses in the wires are inversely proportional to the square of the voltage in the network. Therefore, to transmit electricity over distances of several hundred kilometers, high-voltage power lines (TL) 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 the power system. The Unified Energy System of Russia includes a huge number of power plants controlled from a single center and provides uninterrupted power supply to consumers.

V. GOELRO

1. History

GOELRO (State Commission for the 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.

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

By the end of 1920, the commission had done an enormous amount of work and prepared the Plan for the Electrification of the RSFSR, a volume of 650 pages of text with maps and schemes for the electrification of regions.
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 electric power economy, 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. It was planned to equip the power plants with large boilers and turbines for that time.
One of the main ideas of the plan was the widespread use of the country's vast hydropower resources. Provision was made for a radical reconstruction on the basis of the electrification of all branches of the national economy of the country, and primarily for the growth of heavy industry, and the rational distribution of industry throughout the country.
The implementation of the GOELRO plan began in the difficult conditions of the Civil War and economic devastation.

Since 1947, the USSR has been ranked first in Europe and second in the world in terms of electricity generation.

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 drafting and implementation of the GOELRO plan became possible and 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 of all economic and political power, its strength and will, and also 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 under conditions of rigidly centralized power and predetermined the development of this system for many decades to come.

2. Results

By the end of 1935, the electrical construction program had been overfulfilled by 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, there were 13 power plants of 100,000 kW among the regional power plants.

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 had reached almost 700,000 kW.
The world's largest at that time, the Dnieper hydroelectric power station, Svirskaya 3rd, Volkhovskaya, and others were built. At the highest point of its development, the Unified Energy System of the USSR in many respects surpassed the energy systems of the developed countries of Europe and America.

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

Electricity began to be used in agriculture: in mills, fodder 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 kv. 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 methodical complex. /AND. M. Kogol, G. P. Dubovitsky, V. N. Borodianko, V. S. Gun, N. V. Klinachev, V. V. Krymsky, A. Ya. Ergard, V. A. Yakovlev; Edited by N.V. Klinacheva. - Chelyabinsk, 2006-2008.
Electrical systems, v. 3 - Power transmission by alternating and direct current of high voltage, M., 1972.

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Types of power plants Thermal (TPP) - 50% Thermal (TPP) - 50% Hydroelectric power plants (HPP) % Hydroelectric power plants (HPP) % Nuclear (NPP) - 15% Nuclear (NPP) - 15% Alternative sources Alternative energy sources - 2 - 5% (solar energy, fusion energy, tidal energy, wind energy) energy - 2 - 5% (solar energy, fusion energy, tidal energy, wind energy)

Electric current generator Generator converts mechanical energy into electrical energy Generator converts mechanical energy into electrical energy The action of the generator is based on the phenomenon of electromagnetic induction The action of the generator is based on the phenomenon of electromagnetic induction

The frame with current is the main element of the generator. The rotating part is called the ROTOR (magnet). The rotating part is called the ROTOR (magnet). The fixed part is called the STATOR (frame) The fixed part is called the STATOR (frame) When the frame is rotated, penetrating the frame, the magnetic flux changes with time, as a result of which an induction current appears in the frame

Electricity transmission Power transmission lines (TL) are used to transmit electricity to consumers. When transmitting electricity over a distance, it is lost due to heating of the wires (the Joule-Lenz law). Ways to reduce heat loss: 1) Reducing the resistance of the wires, but increasing their diameter (heavy - difficult to hang, and expensive - copper). 2) Reducing the current strength by increasing the voltage.

The impact of thermal power plants on the environment Thermal power plants - lead to thermal air pollution by products of fuel combustion. Hydroelectric power stations - lead to flooding of vast territories that are being withdrawn from land use. Nuclear power plant - can lead to the release of radioactive substances.

The main stages of production, transmission and consumption of electricity 1. Mechanical energy is converted into electrical energy using generators at power plants. 1. Mechanical energy is converted into electrical energy using generators at power plants. 2. Electric voltage is increased to transmit electricity over long distances. 2. Electric voltage is increased to transmit electricity over long distances. 3. Electricity is transmitted at high voltage through high-voltage power lines. 3. Electricity is transmitted at high voltage through high-voltage power lines. 4. When distributing electricity to consumers, the voltage is reduced. 4. When distributing electricity to consumers, the voltage is reduced. 5. When electricity is consumed, it is converted into other types of energy - mechanical, light or internal. 5. When electricity is consumed, it is converted into other types of energy - mechanical, light or internal.

Video lesson 2: Tasks for alternating current

Lecture: Alternating current. Production, transmission and consumption of electrical energy

Alternating current

Alternating current- these are oscillations that can occur in the circuit as a result of connecting it to an alternating voltage source.

It is alternating current that surrounds us all - it is present in all circuits in apartments, it is the alternating current that is transmitted through the wires. However, almost all electrical appliances run on permanent electricity. That is why at the output from the outlet the current is rectified and in the form of a constant goes to household appliances.

It is alternating current that is easiest to receive and transmit over any distance.

In the study of alternating current, we will use a circuit in which we will connect a resistor, a coil and a capacitor. In this circuit, the voltage is determined according to law:

As we know, the sine can be negative and positive. That is why the voltage value can take a different direction. With a positive direction of current flow (counterclockwise), the voltage is greater than zero, with a negative direction, it is less than zero.

Resistor in the circuit

So let's consider the case where only a resistor is connected to the AC circuit. The resistance of the resistor is called active. We will consider the current that flows counterclockwise in the circuit. In this case, both current and voltage will be positive.

To determine the current strength in the circuit, use the following formula from Ohm's law:

In these formulas I 0 And U 0 - maximum values ​​of current and voltage. From this we can conclude that the maximum current value is equal to the ratio of the maximum voltage to the active resistance:

These two quantities change in the same phase, so the graphs of the quantities have the same form, but different amplitudes.

Capacitor in the circuit

Remember! It is impossible to get direct current in the circuit where there is a capacitor. It is a place for breaking the flow of current and changing its amplitude. In this case, alternating current flows perfectly through such a circuit, changing the polarity of the capacitor.

When considering such a circuit, we will assume that it contains only a capacitor. The current flows counterclockwise, that is, it is positive.

As we already know, the voltage across a capacitor is related to its ability to store charge, that is, its size and capacity.

Since the current is the first derivative of the charge, it is possible to determine by what formula it can be calculated by finding the derivative from the last formula:

As you can see, in this case, the current strength is described by the cosine law, while the value of voltage and charge can be described by the sine law. This means that the functions are in the opposite phase and have a similar appearance on the graph.

We all know that the cosine and sine functions of the same argument differ by 90 degrees from each other, so we can get the following expressions:

From here, the maximum value of the current strength can be determined by the formula:

The value in the denominator is the resistance across the capacitor. This resistance is called capacitive. It is located and marked as follows:

With an increase in capacitance, the amplitude value of the current drops.

Please note that in this circuit, the use of Ohm's law is appropriate only when it is necessary to determine the maximum value of the current; it is impossible to determine the current at any time according to this law due to the phase difference between the voltage and current strength.

Coil in a chain

Consider a circuit in which there is a coil. Imagine that it has no active resistance. In this case, it would seem that nothing should impede the movement of current. However, it is not. The thing is that when the current passes through the coil, a vortex field begins to arise, which prevents the passage of current as a result of the formation of a self-induction current.

The current strength takes the following value:

Again, you can see that the current changes according to the cosine law, so the phase shift is valid for this circuit, which can also be seen on the graph:

Hence the maximum current value:

In the denominator we can see the formula by which the inductive reactance of the circuit is determined.

The greater the inductive reactance, the less important is the amplitude of the current.

Coil, resistance and capacitor in a circuit.

If all types of resistance are simultaneously present in the circuit, then the value of the current can be determined as follows, by converting Ohm's law:

The denominator is called impedance. It consists of the sum of the squares of active (R) and reactance, consisting of capacitive and inductive. The total resistance is called "Impedance".

Electricity

It is impossible to imagine modern life without the use of electrical appliances that operate on the energy generated by an electric current. All technological progress is based on electricity.

Getting energy from electric current has a huge number of advantages:

1. Electricity is relatively easy to produce, as there are billions of power plants, generators and other devices for generating electricity around the world.

2. It is possible to transmit electricity over long distances in a short time and without significant losses.

3. It is possible to convert electrical energy into mechanical, light, internal and other forms.

Electricity transmission is a process that consists in the supply of electricity to consumers. Electricity is produced at remote sources of production (power plants) by huge generators using coal, natural gas, water, nuclear fission or wind.

The current is transmitted through transformers, which increase its voltage. It is high voltage that is economically beneficial when transmitting energy over long distances. High-voltage power lines stretch throughout the country. Through them, electric current reaches substations near large cities, where its voltage is lowered and sent to small (distribution) power lines. Electric current travels through distribution lines in every district of the city and enters transformer boxes. Transformers reduce the voltage to a certain standard value, which is safe and necessary for the operation of household appliances. Current enters the house through wires and passes through a meter that shows the amount of energy consumed.

A transformer is a static device that converts alternating current of one voltage into alternating current of another voltage without changing its frequency. It can only work on AC.

The main structural parts of the transformer

The device consists of three main parts:

1. primary winding of the transformer. The number of turns N 1.
2. The core of the closed form from magnetically soft material (for example, steel).
3. secondary winding. Number of turns N 2 .

In the diagrams, the transformer is depicted as follows:

Principle of operation

The operation of a power transformer is based on Faraday's law of electromagnetic induction.

Between two separate windings (primary and secondary), which are connected by a common magnetic flux, mutual induction appears. Mutual induction is the process by which a primary winding induces a voltage in a secondary winding located in its immediate vicinity.

The primary winding receives an alternating current, which produces a magnetic flux when connected to a power source. The magnetic flux passes through the core and, since it changes over time, it excites induction EMF in the secondary winding. The voltage on the second winding may be lower than on the first, then the transformer is called step-down. The step-up transformer has a higher voltage on the secondary winding. The current frequency remains unchanged. Effective stepping down or stepping up the voltage cannot increase the electrical power, so the current output of the transformer increases or decreases proportionally accordingly.

For the amplitude values ​​of the voltage on the windings, the following expression can be written:

k - transformation ratio.

For step-up transformer k>1, and for step-down - k<1.

During the operation of a real device, there are always energy losses:

• windings are heated.
• work is expended on the magnetization of the core;
• Foucault currents arise in the core (they have a thermal effect on the massive core).

To reduce losses during heating, transformer cores are made not from a single piece of metal, but from thin plates, between which a dielectric is located.

Electrical energy is produced at various scales of power stations, mainly with the help of induction electromechanical generators.

Power generation

There are two main types of power plants:

1. Thermal.

2. Hydraulic.

This division is caused by the type of motor that turns the generator rotor. IN thermal power plants use fuel as an energy source: coal, gas, oil, oil shale, fuel oil. The rotor is driven by steam gas turbines.

The most economical are thermal steam turbine power plants (TPPs). Their maximum efficiency reaches 70%. This is taking into account the fact that the exhaust steam is used in industrial enterprises.

On the hydroelectric power plants the potential energy of water is used to rotate the rotor. The rotor is driven by hydraulic turbines. The power of the station will depend on the pressure and mass of water passing through the turbine.

Electricity use

Electrical energy is used almost everywhere. Of course, most of the electricity produced comes from industry. In addition, transport will be a major consumer.

Many railway lines have long switched to electric traction. Lighting of dwellings, city streets, industrial and domestic needs of villages and villages - all this is also a large consumer of electricity.

A huge part of the electricity received is converted into mechanical energy. All mechanisms used in industry are driven by electric motors. There are enough consumers of electricity, and they are everywhere.

And electricity is produced only in a few places. The question arises about the transmission of electricity, and over long distances. When transmitting over long distances, there is a lot of power loss. Mainly, these are losses due to heating of electrical wires.

According to the Joule-Lenz law, the energy spent on heating is calculated by the formula:

Since it is almost impossible to reduce the resistance to an acceptable level, it is necessary to reduce the current strength. To do this, increase the voltage. Usually there are step-up generators at the stations, and step-down transformers at the end of the transmission lines. And already from them energy disperses to consumers.

The need for electrical energy is constantly increasing. There are two ways to meet demand for increased consumption:

1. Construction of new power plants

2. Use of advanced technology.

Efficient use of electricity

The first method requires the expenditure of a large number of construction and financial resources. It takes several years to build one power plant. In addition, for example, thermal power plants consume a lot of non-renewable natural resources and harm the natural environment.