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HV Power Transmission
A high-capacity hydrogenerator produces an a.c. current at 22,000 V. The current with the potential difference of 220,000 V is produced by means of the transformers at a step-up station and then transmitted over the power lines.
The current potential difference is lowered to medium 6,600 V at the main step-down substation at the end of the line. From here the power is transmitted to the next substations. Transformers stepping the voltage down from 6,600 V are installed at those substations.
Due to voltage conversion, alternating current is used widely in industry. Direct current for battery charging for trams, trolleybuses and electric locomotives is changed from alternating current by means of rectifiers.
Superconductivity
In the electric generating field, as well as in the electric-transmission and storage-technology areas, considerable attention is focused on the use of superconductivity conductors. Cooling an electric conductor to temperatures close to absolute zero (-273°C) results in the conductors' losing their resistance to electric current. Accordingly, their ohmic losses also drop greatly. Current densities of tens of millions amperes per sq cm can be tolerated in such conductors.
Cryogenic technology being now mastered, one can foresee the possibility of supercooling not only generators but also underground transmission lines and storage coils.
1. Where is the current potential difference lowered?
2. Where is the main step-down substation installed?
3. Conductors can never lose their resistance to the flow of electric current?
4. Generators and underground transmission lines can be supercooled?
Unit III
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Atomic Power Plant
Atomic power plants are modern installations. They consist of several main units and a great number of auxiliary ones.
In a nuclear reactor uranium is utilized as s fuel. During operation process powerful heat and radioactive radiation are produced. The nuclear reactor is cooled by water circulation. Cooling water circulates through a system of tubes, in which the water is heated to a temperature of 250-300oC. In order to prevent boiling of water, it passes into the reactor at a pressure up to 150 atmospheres.
A steam generator includes a series of heat exchangers comprising tubes. The water heated in the reactor is delivered into the heat exchanger tubes. The water to be converted into steam flows outside these tubes. The steam produced is fed into the turbogenerator.
Besides, an atomic power plant comprises a common turbogenerator, a steam condenser with circulating water and a switchboard.
Atomic power plants have their advantages as well disadvantages. The reactor and steam generators operate in them noiselessly; the atmosphere is not polluted by dust and smoke. As to the fuel consumption, it is of no special importance and there is no problem of fuel transportation.
The disadvantage of power plants utilizing nuclear fuel is their radiation. Radioactive radiation produced in the reactors is dangerous for attending personnel. Therefore, reactors and steam generators are installed underground. They are also shielded by thick (up to 1.5 m) concrete walls. All their controls are operated by means of automatic devices. These measures serve to protect people from radioactive radiation.
Protection Against Environmental Pollution
Any operating nuclear power plant releases fission products into the environment, which causes environmental pollution.
To prevent the harmful effects of nuclear power release, the nuclear power plants are supplied with protective installations that serve as barriers to the pollution.
First, the nuclear fuel and the fission products are confined within sealed tubes made of stainless steel or zirconium. Then the assembly of tubes is placed in a steel reactor vessel. And finally the steel reactor vessel is placed in a large steel and concrete housing.
As to the hot radioactive waste products they are disposed in heavily shielded cylinders. The cylinders are buried 305 to 610 metres underground.
Vocabulary
Exchanger- теплообменник
steam- пар
tube- труба, лампа
dust- пыль
attending personnel- обслуживающий персонал
to deliver- поставлять
to pollute- загрязнить
to shield- защищать
concrete- бетон
environment- окружающая среда
fission- расщепление
(stainless) steel-(нержавеющая) сталь
vessel- сосуд
waste- отходы
to confine- заключать
to release- выпускать, освобождать
to withstand- противостоять
to dispose- устранять, убирать
2. Выполните упражнения:
1) Подберите русские эквиваленты к словосочетаниям:
nuclear fuel _______________________________________
nuclear fission_________________________________________________
steel vessel____________________________ ________________________
reactor vessel __________________________________________
fission release __________________________________________
sealed tubes __________________________________________
concrete housing_______________________________________________
waste products________________________________________________
nuclear waste_________________________________________________
shielded cylinders ______________________________________________________
2)Употребите глагол в скобках в правильной форме:
1. The experiment (repeat) many times.
2. The power which (radiate) as light is almost three times as great as that radiated as heat.
3. It (know) that iron molecules are magnets at all times.
4. Under ordinary room lightning the resistance of transistors (decrease) millions of times.
5. Ruby crystals about ten centimetres long can (intensify) light ten times.
6. The density of a semiconductor laser radiation (be) hundreds of times as great as that of the ruby laser.
7. The power which (transmit) along a wire is the product of the voltage times the amperage.
3) Завершите предложение, используя правильный вариант:
1. A nuclear reactor is used in a) wind-power plants.
b) atomic power plants.
2. A nuclear reactor is cooled a) water circulating in tubes.
by b) oil circulating in tubes.
3. Water is passed into the reactor a) at a low pressure.
b) at a high pressure.
4. High pressure a) activates boiling of water.
b) prevents boiling of water.
5. Atomic power plants a) pollute the air with dust and smoke.
b) do not pollute the air with dust and smoke.
6. Circulating water flows a) inside the heat exchangers.
b) outside the heat exchangers.
7. Attending personnel is a) thick concrete walls.
shielded by b) thick metal walls.
4) Ответьте на вопросы :
1. What are the main units of an atomic power plant?
2. By what means is the nuclear reactor cooled?
3. At what pressure does the water pass into the reactor?
5)Ответьте, верны ли следующие утверждения:
a) Atomic power plants do not pollute the air with dust and smoke
б) Circulating water flows inside the heat exchangers.
в) A nuclear power plant releases fission products.
г) The waste products are disposed in a shielded cylinders.
д) The fission products are confined within open tubes.
3. Control text
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Solar Energy
The Sun radiates to our planet great amounts of energy. This energy input fuels all our biological processes and is the original source for hydropower, wind power, and fossil fuel resources. Environmentally and economically, the Sun is our greatest energy source. Why then is the direct use of solar energy so limited for industrial, domestic, commercial, and transportation purposes?
First, solar energy arrives in small quantities - only about one kW per square meter; second, it does not arrive at all during night hours. Third, it is very difficult to transform it into useful energy forms except low-grade heat.
Dynamo
Dynamo is a common device for converting mechanical energy into electric energy. This process depends on the fact that if an electrical conductor moves across a magnetic field, an electric current flows in the conductor.
Usually a dynamo includes an electromagnet, called the field magnet, between the poles of which a suitable conductor, usually in the form of a coil, called the armature, is rotated. The mechanical energy of the rotation, in the form of a current in the armature, is thus converted into electric energy.
1. What device is described in the text?
2. What types of the device do you know?
3. Why is the direct use of solar energy limited nowadays?
Unit IV
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Electric Power.
Electric power is generated by converting heat, light, chemical energy, or mechanical energy to electrical energy. Most electrical energy is produced in large power stations be the conversion of mechanical energy or heart. The mechanical energy of falling water is used to drive turbine generators in hydroelectric stations, and the heat derived by burning coal, oil, or other fossil fuels is used to operate steam turbines or internal-combustion engines that drive electric generator in a nuclear power plant.
Electricity generated by the conversion of light or chemical energy is used mainly for portable power sources. For example, a photoelectric cell converts the energy from light to electrical energy for operating the energy to electrical energy for starting an automobile engine.
Electric power produced in large power stations generally is transmitted by using an alternating current that reverses direction 25, 0, or 60 times per second. The basic unit for measuring electric power is the watt – the rate at which work is being done in an electric circuit in which the current is one ampere and the electromotive force is one volt.
Rating for power plants are expressed in kilowatts (1,000 watts) or megawatts (1 million watts). Electric energy consumption normally is given in kilowatt-hour – that is, the number of kilowatts used times the number of hours of use. Electricity is clean, inexpensive, and easily transmitted over kong distances. Since the 1880’s, electricity has had an ever-increasing role in improving the standard of living. It now is used to operate lights, pumps, elevators, power tools, furnaces, refrigerators, air-conditioners, radios, television sets, industrial machinery, and many other kinds of equipment. It has been counted that in developed countries about 43% of the electric power is generally used for industrial purposes, 32% in homes, and 21% in commercial enterprises.