Routing lesson.
Lesson 15. Production, transformation, distribution, accumulation and transmission of energy as technology
Lesson objectives:
Formation of concepts: production, transformation, distribution, accumulation and transmission of energy;
Updating information from personal experience;
Development logical thinking;
Formation of skills in working with information;
Ability to work in groups and individually.
1Children take their seats and check for supplies
Personal UUD:
- formation of self-organization skills
Verification homework
Oral survey:
What is technology?
What is the importance of technology for production?
Why do new technologies emerge?
Communication UUD:
Personal UUD:
Formulating lesson objectives
The topic of our lesson today“Production, transformation, distribution, accumulation and transmission of energy as technology”
Regulatory UUD:
Ability to set a learning task
Explanation of the lesson topic
All technological processes of any production are associated with energy consumption.
The most important role plays at an industrial plant Electric Energy- most universal look energy, which is the main source of mechanical energy.
Conversion energy various types the electrical happens onpower plants.
Power plants are enterprises or installations designed to produce electricity. The fuel for power plants is natural resources - coal, peat, water, wind, sun, nuclear energy, etc.
Depending on the type of energy being converted, power plants can be divided into the following main types: thermal, nuclear, hydroelectric power plants, wind, solar, etc.
The bulk of electricity (up to 80%) is generated at thermal power plants (TPPs). The process of obtaining electrical energy at thermal power plants consists of sequential conversion of the energy of burned fuel into thermal energy water steam driving the turbine unit (steam turbine connected to a generator). The mechanical energy of rotation is converted by the generator into electrical energy. The fuel for power plants is coal, peat, oil shale, natural gas, oil, fuel oil, wood waste.
Nuclear power plants (NPPs) differ from a conventional steam turbine station in that a nuclear power plant uses the process of fission of uranium, plutonium, thorium, etc. nuclei as an energy source. As a result of the splitting of these materials in special devices - reactors, a huge amount of thermal energy is released.
Compared to thermal power plants, nuclear power plants consume a small amount of fuel. Such stations can be built anywhere, because they are not related to the location of natural fuel reserves. In addition, the environment is not polluted by smoke, ash, dust and sulfur dioxide.
In hydroelectric power plants (HPPs), water energy is converted into electrical energy using hydraulic turbines and generators connected to them.
The advantages of hydroelectric power plants are their high efficiency and low cost of generated electricity. However, one should take into account the high cost of capital costs in the construction of hydroelectric power plants and the significant time required for their construction, which determines their long payback period.
A peculiarity of the operation of power plants is that they must generate as much energy as is currently required to cover the load of consumers, the stations’ own needs and losses in the networks. Therefore, station equipment must always be ready for periodic changes in consumer load throughout the day or year.
Electrical energy generated at power plants must behand over to places of its consumption, primarily to large industrial centers of the country, which are many hundreds and sometimes thousands of kilometers away from powerful power plants. But transmitting electricity is not enough. It must be distributed among many different consumers - industrial enterprises, transport, residential buildings, etc. Transmission occurs through transformer substations and electrical networks.
Interruptions in the power supply to enterprises, even short-term ones, lead to disruptions technological process, product damage, equipment damage and irreparable losses. In some cases, a power outage can create an explosion and fire hazard in enterprises.
Distribution Electricity is produced using electrical wiring - a collection of wires and cables with associated fastenings, supporting and protective structures.
Personal UUD:
- consolidation of the knowledge component
Speech development
Ability to briefly formulate ideas
Ability to give examples from personal experience
Reading Skill Development
Consolidation educational material
Answer the test questions:
What are thermal power plants, nuclear power plants, hydroelectric power plants?
Where does the conversion of various types of energy into electrical energy take place?
What is the advantage of a nuclear power plant over a thermal power plant?
How does electricity transfer occur?
Why are interruptions in the power supply to enterprises dangerous?
Communication UUD:
Ability to listen and correct the mistakes of othersPersonal UUD:
Formation of writing skills
Development of logical thinking
Lesson summary
Test checking, grading.
Personal UUD:
- development of self-esteem
Electricity is produced at power plants, often using electromechanical induction generators. There are 2 main types of power plants − thermal power plants(TPP) and hydroelectric power plants (HPP) - differing in the nature of the engines that rotate the rotors of the generators.
The source of energy at thermal power plants is fuel: fuel oil, oil shale, oil, coal dust. The rotors of electric generators are driven into rotation using steam and gas turbines or engines internal combustion(ICE).
As is known, the efficiency of heat engines increases with increasing initial temperature of the working fluid. Therefore, the steam that enters the turbine is brought to about 550 °C at a pressure of about 25 MPa. The efficiency of thermal power plants reaches 40%.
At thermal power plants (CHP), most of the energy from waste steam is used in industrial enterprises and for domestic needs. The efficiency of thermal power plants can reach 60-70%.
At hydroelectric power stations, the potential energy of water is used to rotate the rotors of generators. The rotors are driven by hydraulic turbines.
The power of the station depends on the difference in water levels that are created by the dam (pressure), and on the mass of water that passes through the turbine in 1 second (water flow).
Part of the electricity consumed in Russia (approximately 10%) is produced at nuclear power plants (NPP).
Electricity transmission.
Basically, this process is accompanied by significant losses that are associated with the heating of power line wires by current. According to the Joule-Lenz law, the energy that is spent on heating the wires is proportional to the square of the current strength and the resistance of the line, so if the line is long, transmitting electricity can become economically unprofitable. Therefore, it is necessary to reduce the current, which, for a given transmitted power, leads to the need to increase the voltage. The longer the power line, the more profitable it is to use higher voltages (on some, the voltage reaches 500 kV). Generators alternating current produce voltages that cannot exceed 20 kV (which is due to the properties of the insulating materials used).
Therefore, step-up transformers are installed at power plants, which increase the voltage and reduce the current by the same amount. To supply electricity consumers with the required (low) voltage, step-down transformers are installed at the ends of the power transmission line. Voltage reduction is usually done in stages.
Electricity use.
Main consumers of electricity:
- industry - 70%;
- transport (electric traction);
- household consumers (home lighting, electrical appliances).
Almost all electrical energy used is converted into mechanical energy. Almost all mechanisms in industry are driven by electric motors.
About a third of the electricity consumed by industry is used for technological purposes (electric welding, electric heating and melting of metals, electrolysis, and so on).
in physics
on the topic “Production, transmission and use of electricity”
11th grade A students
Municipal educational institution No. 85
Catherine.
Abstract plan.
Introduction.
1. Electricity production.
1. types of power plants.
2. alternative energy sources.
2. Electricity transmission.
- transformers.
3. Electricity use.
Introduction.
The birth of energy occurred several million years ago, when people learned to use fire. Fire gave them warmth and light, was a source of inspiration and optimism, a weapon against enemies and wild animals, a remedy, an assistant in agriculture, a food preservative, technological means etc.
The wonderful myth about Prometheus, who gave people fire, appeared in Ancient Greece much later than in many parts of the world, quite sophisticated methods of handling fire, its production and extinguishing, preserving fire and rational use of fuel were mastered.
For many years, fire was maintained by burning plant energy sources (wood, shrubs, reeds, grass, dry algae, etc.), and then it was discovered that it was possible to use fossil substances to maintain fire: coal, oil, shale, peat.
Today, energy remains the main component of human life. It makes it possible to create various materials, is one of the main factors in the development of new technologies. Simply put, without mastering various types of energy, a person is not able to fully exist.
Power generation.
Types of power plants.
Thermal power plant (TPP), a power plant that generates electrical energy as a result of the conversion of thermal energy released during the combustion of fossil fuels. The first thermal power plants appeared at the end of the 19th century and became widespread. In the mid-70s of the 20th century, thermal power plants were the main type of power plants.
In thermal power plants, the chemical energy of the fuel is converted first into mechanical energy and then into electrical energy. The fuel for such a power plant can be coal, peat, gas, oil shale, and fuel oil.
Thermal power plants are divided into condensation(IES), designed to generate only electrical energy, and combined heat and power plants(CHP), producing, in addition to electrical energy, thermal energy in the form hot water and a couple. Large CPPs of regional significance are called state district power plants (SDPPs).
The simplest circuit diagram A coal-fired IES is shown in the figure. Coal is fed into the fuel bunker 1, and from it into the crushing unit 2, where it turns into dust. Coal dust enters the furnace of a steam generator (steam boiler) 3, which has a system of tubes in which chemically purified water, called feedwater, circulates. In the boiler, the water is heated, evaporated, and the resulting saturated steam is brought to a temperature of 400-650 °C and, under a pressure of 3-24 MPa, enters steam turbine 4 through a steam line. Steam parameters depend on the power of the units.
Thermal condensing power plants have low efficiency (30-40%), since most of the energy is lost with flue gases and condenser cooling water. It is advantageous to build CPPs in close proximity to fuel production sites. In this case, electricity consumers may be located at a considerable distance from the station.
Combined heat and power plant differs from a condensing station by having a special heating turbine installed on it with steam extraction. At a thermal power plant, one part of the steam is completely used in the turbine to generate electricity in the generator 5 and then enters the condenser 6, and the other, having a higher temperature and pressure, is taken from the intermediate stage of the turbine and is used for heat supply. The condensate is supplied by pump 7 through the deaerator 8 and then by the feed pump 9 to the steam generator. The amount of steam taken depends on the thermal energy needs of enterprises.
Coefficient useful action CHP reaches 60-70%. Such stations are usually built near consumers - industrial enterprises or residential areas. Most often they run on imported fuel.
Thermal stations with gas turbine(GTPP), steam-gas(PHPP) and diesel plants.
Gas or liquid fuel is burned in the combustion chamber of a gas turbine power plant; combustion products with a temperature of 750-900 ºС enter a gas turbine that rotates an electric generator. The efficiency of such thermal power plants is usually 26-28%, power - up to several hundred MW . GTPPs are usually used to cover electrical load peaks. The efficiency of PGES can reach 42 - 43%.
The most economical are large thermal steam turbine power plants (abbreviated TPP). Most thermal power plants in our country use coal dust as fuel. To generate 1 kWh of electricity, several hundred grams of coal are consumed. In a steam boiler, over 90% of the energy released by the fuel is transferred to steam. In the turbine, the kinetic energy of the steam jets is transferred to the rotor. The turbine shaft is rigidly connected to the generator shaft.
Modern steam turbines for thermal power plants are very advanced, high-speed, highly economical machines with a long service life. Their power in a single-shaft version reaches 1 million 200 thousand kW, and this is not the limit. Such machines are always multi-stage, that is, they usually have several dozen disks with working blades and the same number, in front of each disk, of groups of nozzles through which a stream of steam flows. The pressure and temperature of the steam gradually decrease.
It is known from a physics course that the efficiency of heat engines increases with increasing initial temperature of the working fluid. Therefore, the steam entering the turbine is brought to high parameters: temperature - almost 550 ° C and pressure - up to 25 MPa. The efficiency of thermal power plants reaches 40%. Most of the energy is lost along with the hot exhaust steam.
Hydroelectric station (hydroelectric power station), a complex of structures and equipment through which the energy of water flow is converted into electrical energy. A hydroelectric power station consists of a series circuit hydraulic structures, providing the necessary concentration of water flow and creating pressure, and power equipment that converts the energy of water moving under pressure into mechanical rotational energy, which, in turn, is converted into electrical energy.
The pressure of a hydroelectric power station is created by the concentration of the fall of the river in the area used by the dam, or derivation, or a dam and diversion together. The main power equipment of the hydroelectric power station is located in the hydroelectric power station building: in the turbine room of the power plant - hydraulic units, auxiliary equipment, devices automatic control and control; in the central control post - operator-dispatcher console or auto operator of a hydroelectric power station. Increasing transformer substation It is located both inside the hydroelectric power station building and in separate buildings or in open areas. Switchgears often located in an open area. The hydroelectric power station building can be divided into sections with one or more units and auxiliary equipment, separated from adjacent parts of the building. An installation site is created at or inside the hydroelectric power station building for the assembly and repair of various equipment and for auxiliary operations for the maintenance of the hydroelectric power station.
According to installed capacity (in MW) distinguish between hydroelectric power stations powerful(over 250), average(up to 25) and small(up to 5). The power of a hydroelectric power station depends on the pressure (the difference between the levels of the upstream and downstream ), water flow used in hydraulic turbines and the efficiency of the hydraulic unit. For a number of reasons (due to, for example, seasonal changes in the water level in reservoirs, fluctuations in the load of the power system, repairs of hydraulic units or hydraulic structures, etc.), the pressure and flow of water continuously change, and, in addition, the flow changes when regulating the power of a hydroelectric power station. There are annual, weekly and daily cycles of hydroelectric power station operation.
Based on the maximum used pressure, hydroelectric power stations are divided into high-pressure(more than 60 m), medium pressure(from 25 to 60 m) And low-pressure(from 3 to 25 m). On lowland rivers pressures rarely exceed 100 m, in mountainous conditions, a dam can create pressures of up to 300 m and more, and with the help of derivation - up to 1500 m. The division of hydroelectric power stations according to the pressure used is of an approximate, conditional nature.
According to the pattern of water resource use and pressure concentration, hydroelectric power stations are usually divided into channel , dam , diversion with pressure and non-pressure diversion, mixed, pumped storage And tidal .
In run-of-river and dam-based hydroelectric power plants, the water pressure is created by a dam that blocks the river and raises the water level in the upper pool. At the same time, some flooding of the river valley is inevitable. Run-of-river and dam-side hydroelectric power stations are built both on lowland high-water rivers and on mountain rivers, in narrow compressed valleys. Run-of-river hydroelectric power stations are characterized by pressures up to 30-40 m.
At higher pressures, it turns out to be inappropriate to transfer hydrostatic water pressure to the hydroelectric power station building. In this case the type is used dam A hydroelectric power station, in which the pressure front is blocked along its entire length by a dam, and the hydroelectric power station building is located behind the dam, is adjacent to the tailwater.
Another type of layout dammed The hydroelectric power station corresponds to mountain conditions with relatively low river flows.
IN derivational Hydroelectric power station concentration of the river fall is created through diversion; water at the beginning of the used section of the river is diverted from the river bed by a conduit with a slope significantly less than the average slope of the river in this section and with straightening the bends and turns of the channel. The end of the diversion is brought to the location of the hydroelectric power station building. Waste water is either returned to the river or supplied to the next diversion hydroelectric power station. Diversion is beneficial when the river slope is high.
A special place among hydroelectric power stations is occupied by pumped storage power plants(PSPP) and tidal power plants(PES). The construction of pumped storage power plants is due to the growing demand for peak power in large energy systems, which determines the generating power required to cover peak loads. The ability of pumped storage power plants to accumulate energy is based on the fact that free electrical energy in the power system for a certain period of time is used by pumped storage power plant units, which, operating in pump mode, pump water from the reservoir into the upper storage pool. During peak load periods, the accumulated energy is returned to the power system (water from the upper pool enters the pressure pipeline and rotates hydraulic units operating as a current generator).
PES convert the energy of sea tides into electricity. The electricity of tidal hydroelectric power stations, due to some features associated with the periodic nature of the ebb and flow of tides, can be used in energy systems only in conjunction with the energy of regulating power plants, which make up for the power failures of tidal power stations within days or months.
The most important feature of hydropower resources compared to fuel and energy resources is their continuous renewability. The absence of fuel requirement for hydroelectric power plants determines the low cost of electricity generated by hydroelectric power plants. Therefore, the construction of hydroelectric power stations, despite significant specific capital investments by 1 kW installed capacity and long construction periods were and are given great importance, especially when this is associated with the placement of electricity-intensive industries.
Nuclear power plant (NPP), a power plant in which atomic (nuclear) energy is converted into electrical energy. The energy generator at a nuclear power plant is a nuclear reactor. The heat that is released in the reactor as a result of the fission chain reaction of some nuclei heavy elements, then, just like in conventional thermal power plants (TPP), is converted into electricity. Unlike thermal power plants that run on fossil fuels, nuclear power plants run on nuclear fuel(based on 233 U, 235 U, 239 Pu). It has been established that the world's energy resources of nuclear fuel (uranium, plutonium, etc.) significantly exceed the energy resources of natural reserves of organic fuel (oil, coal, natural gas, etc.). This opens up broad prospects for meeting rapidly growing fuel demands. In addition, it is necessary to take into account the ever-increasing volume of coal and oil consumption for technological purposes in the global chemical industry, which is becoming a serious competitor to thermal power plants. Despite the discovery of new deposits of organic fuel and the improvement of methods for its production, there is a tendency in the world towards a relative increase in its cost. This creates the most difficult conditions for countries with limited reserves of fossil fuels. There is an obvious need for the rapid development of nuclear energy, which already occupies a prominent place in the energy balance of a number of industrial countries around the world.
A schematic diagram of a nuclear power plant with a water-cooled nuclear reactor is shown in Fig. 2. Heat released in core reactor coolant, is taken in by water from the 1st circuit, which is pumped through the reactor by a circulation pump. Heated water from the reactor enters the heat exchanger (steam generator) 3, where it transfers the heat received in the reactor to the water of the 2nd circuit. The water of the 2nd circuit evaporates in the steam generator, and steam is formed, which then enters the turbine 4.
Most often, 4 types of thermal neutron reactors are used at nuclear power plants:
1) water-water with ordinary water as a moderator and coolant;
2) graphite-water with water coolant and graphite moderator;
3) heavy water with water coolant and heavy water as a moderator;
4) graffito - gas with gas coolant and graphite moderator.
The choice of the predominantly used type of reactor is determined mainly by the accumulated experience in the carrier reactor, as well as the availability of the necessary industrial equipment, raw material reserves, etc.
The reactor and its servicing systems include: the reactor itself with biological protection , heat exchangers, pumps or gas-blowing units that circulate the coolant, pipelines and fittings for the circulation circuit, devices for reloading nuclear fuel, special ventilation systems, emergency cooling systems, etc.
To protect nuclear power plant personnel from radiation exposure, the reactor is surrounded by biological shielding, the main materials for which are concrete, water, and serpentine sand. The reactor circuit equipment must be completely sealed. A system is provided to monitor places of possible coolant leaks; measures are taken to ensure that leaks and breaks in the circuit do not lead to radioactive emissions and contamination of the nuclear power plant premises and the surrounding area. Radioactive air and a small amount of coolant vapor, due to the presence of leaks from the circuit, are removed from unattended rooms of the nuclear power plant special system ventilation, in which cleaning filters and holding gas tanks are provided to eliminate the possibility of air pollution. The compliance with radiation safety rules by NPP personnel is monitored by the dosimetry control service.
Availability biological protection, special ventilation and emergency cooling systems and dosimetric monitoring services make it possible to completely protect NPP operating personnel from the harmful effects of radioactive radiation.
Nuclear power plants, which are the most modern look power plants have a number of significant advantages over other types of power plants: when normal conditions functioning they do not pollute at all environment, do not require connection to a source of raw materials and, accordingly, can be placed almost anywhere. New power units have a capacity almost equal to that of an average hydroelectric power station, but the installed capacity utilization factor at a nuclear power plant (80%) significantly exceeds this figure for a hydroelectric power station or thermal power plant.
NPPs have practically no significant disadvantages under normal operating conditions. However, one cannot fail to notice the danger of nuclear power plants under possible force majeure circumstances: earthquakes, hurricanes, etc. - here old models of power units pose a potential danger of radiation contamination of territories due to uncontrolled overheating of the reactor.
Alternative energy sources.
Energy of sun.
IN Lately interest in the problem of using solar energy has increased sharply, because the potential of energy based on the use of direct solar radiation, are extremely large.
The simplest solar radiation collector is a blackened metal (usually aluminum) sheet, inside of which there are pipes with a liquid circulating in it. Heated by solar energy absorbed by the collector, the liquid is supplied for direct use.
Solar energy is one of the most material-intensive types of energy production. Large-scale use of solar energy entails a gigantic increase in the need for materials, and, consequently, in labor resources for the extraction of raw materials, their enrichment, obtaining materials, manufacturing heliostats, collectors, other equipment, and their transportation.
Electrical energy generated by solar rays is still much more expensive than that obtained traditional ways. Scientists hope that the experiments they will conduct at pilot installations and stations will help solve not only technical, but also economic problems.
Wind energy.
Enormous energy of moving air masses. The reserves of wind energy are more than a hundred times greater than the hydropower reserves of all the rivers on the planet. Winds blow constantly and everywhere on earth. Climatic conditions allow the development of wind energy over a vast territory.
But today, wind engines supply just one thousandth of the world's energy needs. Therefore, aircraft specialists who know how to select the most appropriate blade profile and study it in a wind tunnel are involved in creating the designs of the wind wheel, the heart of any wind power plant. Through the efforts of scientists and engineers, the most various designs modern wind turbines.
Energy of the Earth.
People have long known about the spontaneous manifestations of gigantic energy hidden in the depths of the globe. The memory of mankind preserves legends about catastrophic volcanic eruptions that killed millions human lives, which have changed the appearance of many places on Earth beyond recognition. The power of the eruption of even a relatively small volcano is colossal; it is many times greater than the power of the largest power plants created by human hands. True, there is no need to talk about the direct use of the energy of volcanic eruptions; people do not yet have the ability to curb this rebellious element.
The Earth's energy is suitable not only for heating premises, as is the case in Iceland, but also for generating electricity. Power plants using hot underground springs have been operating for a long time. The first such power plant, still very low-power, was built in 1904 in the small Italian town of Larderello. Gradually, the power of the power plant grew, more and more new units were put into operation, new sources of hot water were used, and today the power of the station has already reached an impressive value of 360 thousand kilowatts.
Electricity transmission.
Transformers.
You purchased a ZIL refrigerator. The seller warned you that the refrigerator is designed for a mains voltage of 220 V. And in your house the mains voltage is 127 V. A hopeless situation? Not at all. You just have to make an additional expense and purchase a transformer.
Transformer- a very simple device that allows you to both increase and decrease voltage. The conversion of alternating current is carried out using transformers. Transformers were first used in 1878 by the Russian scientist P. N. Yablochkov to power the “electric candles” he invented, a new light source at that time. P. N. Yablochkov’s idea was developed by Moscow University employee I. F. Usagin, who designed improved transformers.
The transformer consists of a closed iron core, on which two (sometimes more) coils with wire windings are placed (Fig. 1). One of the windings, called the primary, is connected to the source AC voltage. The second winding, to which the “load” is connected, i.e., instruments and devices that consume electricity, is called secondary.
The operation of a transformer is based on the phenomenon of electromagnetic induction. When alternating current passes through the primary winding, an alternating magnetic flux appears in the iron core, which excites induced emf in each winding. Moreover, the instantaneous value of the induced emf e V any turn of the primary or secondary winding according to Faraday’s law is determined by the formula:
e = - Δ F/ Δ t
If F= Ф 0 сosωt, then
e = ω Ф 0 sin ω t , or
e = E 0 sin ω t ,
Where E 0 = ω Ф 0 - amplitude of the EMF in one turn.
In the primary winding, which has n 1 turns, total induced emf e 1 equal to p 1 e.
In the secondary winding there is a total emf. e 2 equal to p 2 e, Where n 2- the number of turns of this winding.
It follows that
e 1 e 2 = n 1 n 2 . (1)
Sum voltage u 1 , applied to the primary winding, and EMF e 1 should be equal to the voltage drop in the primary winding:
u 1 + e 1 = i 1 R 1 , Where R 1 - active resistance of the winding, and i 1 - current strength in it. This equation follows directly from the general equation. Usually the active resistance of the winding is small and i 1 R 1 can be neglected. That's why
u 1 ≈ -e 1 . (2)
When the secondary winding of the transformer is open, no current flows in it, and the following relationship holds:
u 2 ≈ - e 2 . (3)
Since the instantaneous values of the emf e 1 And e 2 change in phase, then their ratio in formula (1) can be replaced by the ratio of effective values E 1 And E 2 of these EMFs or, taking into account equalities (2) and (3), the ratio of effective voltage values U 1 and U 2 .
U 1 /U 2 = E 1 / E 2 = n 1 / n 2 = k . (4)
Magnitude k called the transformation ratio. If k>1, then the transformer is step-down, when k <1 - increasing
When the secondary winding circuit is closed, current flows in it. Then the ratio u 2 ≈ - e 2 is no longer fulfilled exactly, and accordingly the connection between U 1 and U 2 becomes more complex than in equation (4).
According to the law of conservation of energy, the power in the primary circuit must be equal to the power in the secondary circuit:
U 1 I 1 = U 2 I 2, (5)
Where I 1 And I 2 - effective values of force in the primary and secondary windings.
It follows that
U 1 /U 2 = I 1 / I 2 . (6)
This means that by increasing the voltage several times using a transformer, we reduce the current by the same amount (and vice versa).
Due to the inevitable energy losses due to heat release in the windings and iron core, equations (5) and (6) are satisfied approximately. However, in modern powerful transformers, the total losses do not exceed 2-3%.
In everyday practice we often have to deal with transformers. In addition to those transformers that we use willy-nilly due to the fact that industrial devices are designed for one voltage, and the city network uses another, we also have to deal with car bobbins. The bobbin is a step-up transformer. To create a spark that ignites the working mixture, a high voltage is required, which we obtain from the car battery, after first converting the direct current of the battery into alternating current using a breaker. It is not difficult to understand that, up to the loss of energy used to heat the transformer, as the voltage increases, the current decreases, and vice versa.
Welding machines require step-down transformers. Welding requires very high currents, and the welding machine's transformer has only one output turn.
You probably noticed that the transformer core is made from thin sheets of steel. This is done so as not to lose energy during voltage conversion. In sheet material, eddy currents will play a smaller role than in solid material.
At home you are dealing with small transformers. As for powerful transformers, they are huge structures. In these cases, the core with windings is placed in a tank filled with cooling oil.
Electricity transmission
Electricity consumers are everywhere. It is produced in relatively few places close to sources of fuel and hydro resources. Therefore, there is a need to transmit electricity over distances sometimes reaching hundreds of kilometers.
But transmitting electricity over long distances is associated with noticeable losses. The fact is that as current flows through power lines, it heats them up. In accordance with the Joule-Lenz law, the energy spent on heating the wires of the line is determined by the formula
where R is the line resistance. With a large line length, energy transmission may become generally unprofitable. To reduce losses, you can, of course, follow the path of reducing the resistance R of the line by increasing the cross-sectional area of the wires. But to reduce R, for example, by 100 times, you need to increase the mass of the wire also by 100 times. It is clear that such a large expenditure of expensive non-ferrous metal cannot be allowed, not to mention the difficulties of fastening heavy wires on high masts, etc. Therefore, energy losses in the line are reduced in another way: by reducing the current in the line. For example, reducing the current by 10 times reduces the amount of heat released in the conductors by 100 times, i.e., the same effect is achieved as from making the wire a hundred times heavier.
Since current power is proportional to the product of current and voltage, to maintain the transmitted power, it is necessary to increase the voltage in the transmission line. Moreover, the longer the transmission line, the more profitable it is to use a higher voltage. For example, in the high-voltage transmission line Volzhskaya HPP - Moscow, a voltage of 500 kV is used. Meanwhile, alternating current generators are built for voltages not exceeding 16-20 kV, since a higher voltage would require more complex special measures to be taken to insulate the windings and other parts of the generators.
That's why step-up transformers are installed at large power plants. The transformer increases the voltage in the line by the same amount as it decreases the current. The power losses are small.
To directly use electricity in the electric drive motors of machine tools, in the lighting network and for other purposes, the voltage at the ends of the line must be reduced. This is achieved using step-down transformers. Moreover, usually a decrease in voltage and, accordingly, an increase in current occurs in several stages. At each stage, the voltage becomes less and less, and the territory covered by the electrical network becomes wider. The diagram of transmission and distribution of electricity is shown in the figure.
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Electric power stations in a number of regions of the country are connected by high-voltage transmission lines, forming a common power grid to which consumers are connected. Such an association is called a power system. The power system ensures uninterrupted supply of energy to consumers regardless of their location.
Electricity use.
The use of electrical power in various fields of science.
The twentieth century became the century when science invades all spheres of social life: economics, politics, culture, education, etc. Naturally, science directly influences the development of energy and the scope of application of electricity. On the one hand, science contributes to expanding the scope of application of electrical energy and thereby increases its consumption, but on the other hand, in an era when the unlimited use of non-renewable energy resources poses a danger to future generations, the urgent tasks of science are the development of energy-saving technologies and their implementation in life.
Let's look at these questions using specific examples. About 80% of the growth in GDP (gross domestic product) of developed countries is achieved through technical innovation, the main part of which is related to the use of electricity. Everything new in industry, agriculture and everyday life comes to us thanks to new developments in various branches of science.
Most scientific developments begin with theoretical calculations. But if in the 19th century these calculations were made using pen and paper, then in the age of the STR (scientific and technological revolution) all theoretical calculations, selection and analysis of scientific data, and even linguistic analysis of literary works are done using computers (electronic computers), which operate on electrical energy, which is most convenient for transmitting it over a distance and using it. But if initially computers were used for scientific calculations, now computers have come from science to life.
Now they are used in all areas of human activity: for recording and storing information, creating archives, preparing and editing texts, performing drawing and graphic work, automating production and agriculture. Electronicization and automation of production are the most important consequences of the “second industrial” or “microelectronic” revolution in the economies of developed countries. The development of complex automation is directly related to microelectronics, a qualitatively new stage of which began after the invention in 1971 of the microprocessor - a microelectronic logical device built into various devices to control their operation.
Microprocessors have accelerated the growth of robotics. Most of the robots currently in use belong to the so-called first generation, and are used for welding, cutting, pressing, coating, etc. The second generation robots that are replacing them are equipped with devices for recognizing the environment. And third-generation “intellectual” robots will “see,” “feel,” and “hear.” Scientists and engineers name nuclear energy, space exploration, transport, trade, warehousing, medical care, waste processing, and the development of the riches of the ocean floor among the highest priority areas for using robots. The majority of robots operate on electrical energy, but the increase in electricity consumption by robots is offset by a decrease in energy costs in many energy-intensive production processes due to the introduction of more rational methods and new energy-saving technological processes.
But let's get back to science. All new theoretical developments after computer calculations are tested experimentally. And, as a rule, at this stage, research is carried out using physical measurements, chemical analyzes, etc. Here, scientific research tools are diverse - numerous measuring instruments, accelerators, electron microscopes, magnetic resonance imaging scanners, etc. The bulk of these instruments of experimental science are powered by electrical energy.
Science in the field of communications and communications is developing very rapidly. Satellite communications are no longer used only as a means of international communication, but also in everyday life - satellite dishes are not uncommon in our city. New means of communication, such as fiber technology, can significantly reduce energy losses in the process of transmitting signals over long distances.
Science has not bypassed the sphere of management. As scientific and technological progress develops and the production and non-production spheres of human activity expand, management begins to play an increasingly important role in increasing their efficiency. From a kind of art, which until recently was based on experience and intuition, management today has turned into a science. The science of management, the general laws of receiving, storing, transmitting and processing information is called cybernetics. This term comes from the Greek words “helmsman”, “helmsman”. It is found in the works of ancient Greek philosophers. However, its rebirth actually occurred in 1948, after the publication of the book “Cybernetics” by the American scientist Norbert Wiener.
Before the start of the “cybernetic” revolution, there was only paper computer science, the main means of perception of which was the human brain, and which did not use electricity. The "cybernetic" revolution gave birth to a fundamentally different one - machine informatics, corresponding to the gigantically increased flows of information, the source of energy for which is electricity. Completely new means of obtaining information, its accumulation, processing and transmission have been created, which together form a complex information structure. It includes automated control systems (automated control systems), information data banks, automated information databases, computer centers, video terminals, copying and phototelegraph machines, national information systems, satellite and high-speed fiber-optic communication systems - all this has unlimitedly expanded the scope of electricity use.
Many scientists believe that in this case we are talking about a new “information” civilization, replacing the traditional organization of an industrial-type society. This specialization is characterized by the following important features:
· widespread use of information technology in material and non-material production, in the field of science, education, healthcare, etc.;
· the presence of a wide network of various data banks, including public ones;
· turning information into one of the most important factors in economic, national and personal development;
· free circulation of information in society.
Such a transition from an industrial society to an “information civilization” became possible largely due to the development of energy and the provision of a convenient type of energy for transmission and use - electrical energy.
Electricity in production.
Modern society cannot be imagined without the electrification of production activities. Already at the end of the 80s, more than 1/3 of all energy consumption in the world was carried out in the form of electrical energy. By the beginning of the next century, this share may increase to 1/2. This increase in electricity consumption is primarily associated with an increase in its consumption in industry. The bulk of industrial enterprises operate on electrical energy. High electricity consumption is typical for energy-intensive industries such as metallurgy, aluminum and mechanical engineering.
Electricity in the home.
Electricity is an essential assistant in everyday life. Every day we deal with her, and, probably, we can no longer imagine our life without her. Remember the last time your lights were turned off, that is, there was no electricity coming to your house, remember how you swore that you didn’t have time to do anything and you needed light, you needed a TV, a kettle and a bunch of other electrical appliances. After all, if we were to lose power forever, we would simply return to those ancient times when food was cooked over fires and we lived in cold wigwams.
A whole poem can be dedicated to the importance of electricity in our lives, it is so important in our lives and we are so accustomed to it. Although we no longer notice that it is coming into our homes, when it is turned off, it becomes very uncomfortable.
Appreciate electricity!
Bibliography.
1. Textbook by S.V. Gromov “Physics, 10th grade.” Moscow: Enlightenment.
2. Encyclopedic dictionary of a young physicist. Compound. V.A. Chuyanov, Moscow: Pedagogy.
3. Ellion L., Wilkons U.. Physics. Moscow: Science.
4. Koltun M. World of Physics. Moscow.
5. Energy sources. Facts, problems, solutions. Moscow: Science and Technology.
6. Non-traditional energy sources. Moscow: Knowledge.
7. Yudasin L.S.. Energy: problems and hopes. Moscow: Enlightenment.
8. Podgorny A.N. Hydrogen energy. Moscow: Science.
Page 1 of 42
M. B. Zevin, A. N. Trifonov
The book discusses electrical devices and cable connections to them, the basics of electrical installation work. Much attention is paid to mechanized installation and description of mechanisms and devices developed and put into practice in recent years, as well as the operation and installation of cable lines.
Chapter I. Production and distribution of electrical energy
§ 1. Electric stations
An electrical station (power plant) is a collection of devices and equipment used to produce electrical energy. At power plants, electrical energy is obtained through the use of energy carriers or the transformation of various types of energy. Power plants, based on the type of energy used in them, are divided into thermal, nuclear and hydroelectric.
In thermal power plants, coal, oil or natural gas are burned in boiler furnaces. The resulting heat converts the water in the boilers into steam, which drives the rotors of steam turbines and the rotors of generators connected to them, in which the mechanical energy of the turbines is converted into electrical energy.
At nuclear power plants, the processes of converting steam energy into mechanical and then into electrical energy are similar to the processes occurring in thermal power plants, and differ from the latter in that the “fuel” in them is radioactive elements or their isotopes, which release heat during the decay reaction
In hydroelectric power plants, the energy of water flow is converted into electrical energy.
There are also wind, solar power plants, geothermal, tidal and other power plants that convert respectively moving air flows, the heat of the sun's rays and the bowels of the Earth, and the energy of sea and ocean tides into electrical energy.
Steam turbine thermal power plants are divided into condensing and heating plants. At condensing stations, thermal energy is completely converted into electrical energy, and at heating plants, called combined heat and power plants (CHP), thermal energy is partially converted into electrical energy, and is mainly spent on supplying industrial enterprises and cities with steam and hot water. Therefore, thermal power plants are built near thermal energy consumers. Condensing steam turbine power plants, as a rule, are built near the extraction site of solid fuel - coal, peat, oil shale. During the construction of hydroelectric power stations (HPPs), a set of problems is solved, related not only to the generation of electrical energy and its supply to consumers, but also to the improvement of river navigation, irrigation of arid lands, water supply, etc.
The construction of nuclear power plants (NPPs) is especially advisable in areas where there are no local fuel reserves and rivers with large hydropower resources. They operate on nuclear fuel, which is consumed in small quantities, so its delivery to the power plant does not cause large transport costs.
The transfer of energy generated by powerful hydroelectric power plants, thermal power plants and nuclear power plants to the power grid to supply consumers is usually carried out via high voltage lines (110 kV and above) through step-up transformer substations.
In order to rationally distribute the load between power plants, the most economical generation of electrical energy, better use of the installed capacity of the stations, increasing the reliability of power supply to consumers and supplying them with electrical energy with normal quality indicators in frequency and voltage, parallel operation of power plants on the common electrical network of the regional energy system is widely carried out. In addition to power plants, it also includes power transmission lines of various voltages, network transformer substations and heating networks connected by the common mode of production and distribution of electrical and thermal energy. Many regional energy systems of the Soviet Union are united for parallel operation into a common electrical network and form large energy systems: the Unified Energy System (UES) of the European part of the USSR, the Unified Energy System of Siberia, the Unified Energy System of Kazakhstan, etc.
The further stage in the development of the USSR energy sector will be the unification of energy systems into the Unified Energy System of the Soviet Union: The energy systems of a number of socialist countries are united into the Mir energy system.
Electricity of the net
For the transmission and distribution of electrical energy from power centers of power plants to consumers, they are used. Electricity of the net, which consist of switchgears (RU) and overhead or cable lines of various voltages.
Power Center (CP) is called a generator voltage switchgear of power plants or a secondary voltage switchgear of a step-down substation of the power system, to which the distribution networks of a given area are connected.
Electrical networks can be of direct and alternating current. DC networks mainly include networks of electrified railways, subways, trams, trolleybuses, as well as some electrical networks of chemical, metallurgical and other industrial enterprises. Power supply to all other industrial, agricultural, municipal and domestic facilities is carried out with three-phase alternating current with a frequency of 50 Hz.
The electrical energy generated by turbogenerators and hydrogenerators has voltages of 6000 or 10000 V, and sometimes 20000 V. It is not economically feasible to transmit electrical energy of such voltage over long distances due to significant electrical losses. Therefore, it is increased to 110, 220 and 500 kV at step-up transformer substations built at power plants, and then before being supplied to consumers it is lowered to 35, 10 and 6 kV at step-down transformer substations.
A simplified diagram of energy distribution from power plants to consumers is shown in Fig. 1. From the above diagram it is clear that power plants A, B, C, D and D connected by power transmission lines (PTL) with a voltage of 220 kV. The transmission and distribution of electrical energy is carried out at voltages of 220, 110, 35 and 10 kV. The power supply scheme provides for redundancy of substations at all voltage levels, which helps to avoid interruptions in the supply of electrical energy.
Fig 1. Power system diagram:
A - D -power plants, transformer substations,I-
III-
step-up substations, 1-4 - step-down substations
Overhead or cable lines depart from the switchgear of step-down substations to transmit electrical energy to consumers. Most industrial plants obtain their energy from utility systems and only in rare cases from their own plant power plants. Electricity supply and energy distribution within the enterprise from its own power plants is carried out mainly at generator voltages of 6 and 10 kV.
The power supply and energy distribution scheme depends on the distance between the enterprise and the power source, power consumption, territorial location of loads, requirements for reliable and uninterrupted power supply to electrical receivers, as well as the number of receiving and distribution points at the enterprise.
The presence of large loads concentrated in certain areas of industrial enterprises and in certain areas of large cities accelerates the introduction of deep high-voltage bushings* into the power supply system. Thanks to this, cable distribution networks are significantly reduced and cable products are saved. Deep penetrations are usually constructed with overhead lines for voltages of 35, 110, 220 and 330 kV.
* Deep input- This is a high-voltage sewer from the power system directly to the load center.
Electrical networks are divided into non-redundant, when electrical receivers receive electrical energy from one power source, and redundant, when power is supplied from two or more power sources. The production, transmission and distribution of electrical energy are accompanied by losses in all network elements; cable and overhead lines, transformers, high-voltage devices, etc.
Total losses of electrical energy, including expenses for own needs, reach up to 10%, of which the greatest losses occur in the supply networks from power centers to distribution points.
To reduce electrical energy losses and identify sections and elements of the network with the greatest losses, measurements, calculations and assessments of the rational construction and operation of the network are carried out. Based on these data, measures are taken to reduce electrical energy losses, which mainly boil down to switching the network to higher voltage (if economically feasible), turning off lightly loaded transformers during periods of minimal load.
§ 3. Electricity consumers
The main characteristics of electrical energy consumers are: design load, installation operating mode, reliability of power supply. Based on the calculated load and operating mode of the consumer, the power of the supply transformers and the cross-sections of cable and overhead lines are determined.
To ensure the reliability of power supply, power receivers are divided into three categories.
The first category includes electrical receivers, the failure of the power supply of which entails a danger to human life, significant damage to the national economy, damage to equipment, mass defects of products, disruption of a complex technological process, disruption of the operating mode of particularly important facilities (blast and open-hearth furnaces, some workshops of chemical enterprises , electrified railways, metro).
The second category includes electrical receivers, the interruption in the power supply of which is associated with a massive undersupply of products, downtime of working mechanisms and industrial transport, disruption of the normal operation of a significant number of urban enterprises (garment and shoe factories) and electric transport.
The third category includes electrical receivers that are not included in the first and second categories.
An interruption in the power supply to power receivers of the first category can be allowed only for the period of automatic input of emergency power, of the second category - for the time required to turn on the backup power by the personnel on duty or by an on-site operational team, and for receivers of the third category - for the time necessary to repair or replace the damaged one. element of the power supply system, but not more than a day.
In accordance with the specified requirements for reliability of power supply, power supply of power receivers of the first and second categories is carried out from two independent sources, and the third - from one supply line without mandatory redundancy.
Power supply to industrial enterprises and cities is carried out through switchgears and substations as close as possible to consumers.
Distribution device (RU) is an electrical installation that serves to receive and distribute electrical energy and contains switching devices, busbars and connecting busbars, auxiliary devices (compressor, battery, etc.), as well as protection devices, automation and measuring instruments. Switchgears they construct an open type (ORU), when the main equipment is located in the open air, and a closed type (CLU), when the equipment is located in the building.
An electrical installation used for the conversion and distribution of electrical energy and consisting of transformers or other energy converters, switchgear, control devices and auxiliary structures is called substation. Depending on the predominance of one or another function of substations, they are called transformer (TP) or converter.
A switchgear designed for receiving and distributing electrical energy at one voltage without conversion and transformation and not being part of a substation is called distribution point(RP).
Rice. 2. Two-stage radial power circuit: TsRP - central distribution substation, TP1, RP2 - distribution substations, TP1, TP 2 transformer substations
To distribute electrical energy at voltages of 6 and 10 kV in enterprises and cities, two types of circuits are used: radial (Fig. 2) and main (Fig. 3). These schemes have many varieties, which are determined mainly by the category of electrical receivers, the territorial location and power of substations and energy collection points. The quality of electrical energy is characterized by constant frequency and voltage stability among consumers within the established standards. The frequency is set by power plants for the entire power system as a whole.
Rice. 3. Backbone circuits: A- single with one-way supply, b - ring; RP- distribution substation, TP1 - TP5- transformer substations.
The voltage level changes depending on the network configuration as it approaches the consumer, equipment loading conditions and electrical energy consumption by consumers. The rated voltage of consumers is indicated in the tables.
The voltages of electrical networks and electrical equipment are standardized (Table 1). To compensate for voltage loss in networks, the rated voltages of generators and secondary windings of transformers are taken to be 5% higher than the rated voltages of electrical receivers.
Table 1. Rated voltages (up to 1000 V) of electrical networks and energy sources and receivers connected to them
|
Voltage at direct current, V |
Voltage at alternating current, V |
||||
|
sources and converters |
networks and receivers |
single-phase |
three-phase |
single-phase |
three-phase |
|
sources and converters |
networks and receivers |
||||
Note. The rated voltage (over 1000 V) of electrical networks and receivers, generators and synchronous compensators, as well as the highest operating voltage of electrical equipment are given in GOST 23366-78.
Electrical installation rules determine voltage levels and the procedure for regulating them. The deviation of the voltage at the terminals of electric motors from the nominal voltage, as a rule, is allowed no more than ± 15%. The voltage drop for the most distant lamps of internal working lighting of industrial enterprises and public buildings can be no more than 2.5 %, and the increase is no more than 5% of the nominal value.
Control questions
1. List the names of power plants by the types of energy carriers they use.
2. What are the technical and economic advantages of constructing thermal power plants, hydroelectric power plants and nuclear power plants?
3. What elements does the power system consist of?
4 What is included in the electrical network?
5. What is called RU, TP, RP?
6. What is deep typing?
7. Which elements of the electrical network have the greatest losses of electrical energy?
8. What categories are consumers of electrical energy divided into?