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Unit 5
TRANSMISSION LINES
Energy transmission is one of the basic elements of modern communication. Practically, one can say that communication is carried out due to the energy being transmitted over the transmitting lines. Lines used for energy transmission may be classed into the following three types: overhead, indoor and underground. Naturally, these types are different in construction and in the elements they are made of.
As for overhead lines, they include line conductors, insulators and supports. Indoor lines include conductors, cords and buses. The conductors in indoor lines may include one wire or a combination of wires not insulated from one another. As for underground lines, they usually include line conductors and insulators. Underground lines are laid under ground. They are mostly used in cities and in industrial areas.
The lines are made of thick wires of different metals. A number of metal wires put together form one thick cable and a pair includes two insulated conductors forming a metallic circuit. Thus, the basic technological part of energy transmission process is a long transmission line, and a cable is its main part.
The length of transmitting lines varies greatly since different signals must be transmitted over various distances, from area to area. In the process of transmitting electric energy, heating and radiation losses take place in the lines. The intensity of losses depends on the resistance in the lines. The greater is the resistance in the lines, the greater are the losses of conducting wires. Naturally, the losses must be reduced. The purpose of any energy transmission is to carry energy with as little losses as possible. Conductors and transformers are connected to the lines since they serve as the means of reducing heating and radiation losses.
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Insulate
Bus
Cord ,
Indoor (outdoor) ()
GRAMMAR EXERCISES
I. Translate the following sentences, pay attention to the Infinitive used.
A 1. To transmit a message requires some energy. 2. Computers are used to perform series of mathematical operations. 3. It is quite necessary for the designer to understand the operation of the central processing unit. 4. Active satellites are equipped to receive and retransmit signals. 5. The distance to be covered was equal to 1000.000 miles. 6. To reduce power losses, thick wires should be used. 7. At least 90 per cent of electric energy to be generated at present is AC (alternative current). 8. Selectivity in audio-frequency amplifiers tends to broaden and gain to increase as capacitance is decreased. 9. Various installations are being used to transform electric power into mechanical and heat power.
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B 1. For information to be transmitted, it must be attached to a radio-frequency carrier wave. 2. There exist many problems to be solved in science and technology by means of new techniques. 3. The new device gives fault-free operation and can be fully relied upon. 4. No additional components were used since they were not needed in order to actuate the relay. 5. In modern radio receivers oscillators are used to generate radio frequency waves that can be mixed with the incoming waves. 6. Computers ability to perform operations depends on their ability to store information. 7. The only power required to operate the radio is electrical power. 8. Power supplies are needed to convert the AC voltage to DC and to increase or decrease the voltage to the required value. 9. In case of fault in the line it may be sufficient to make measurements at one end of the line only. 10. When laying the cable, the cable run is to be selected so that to have a minimum possible distance between the starting and the finishing points of the line. 11. The colour television receiver consumes more power then the black-and-white receiver. To be exact, it consumes about one and a half times as much power. 12. It is practically impossible to convert a black-and-white receiver to receive colour broadcasts. To do it will require a great deal of special components.
II. Translate the following sentences, pay attention to the different meanings: "because , ", "because of , , -".
1. Because our sense of temperature is not very reliable temperature measurements of our body must be made with accurate thermometers. 2. The energy, which an object has its motion because is called kinetic energy. 3. Because of the relative complexity of plasma accelerator configurations, experiments are needed to determine the design of suitable plasma drive devices. 4. The problem of power generation from fusion reactors is very difficult because of the difficulty of containing plasma. 5. Because the neutron is neutral the positive charge on the nucleus does not affect it.
LEXICAL EXERCISES
III. Match the meanings of the following word combinations.
| External resistance Internal wiring Complex numbers Simple compression Simple fraction Thin aluminium wire Considerable losses Comparable efficiency Comparison curves Considerable resistance |
IV. Translate the text without dictionary.
As we know, transmission lines belong to the basic parts of the technological sphere of modern communication. In this sphere there operate different types of energy transmission lines. They differ in length, construction and cost. Among different types of transmission lines compressed gas-insulated ones have a number of advantages. Their main advantages are simplicity of construction and comparatively low cost.
The gas-insulated lines include a number of phase conductors and each of them is placed inside a tube. The tube space is not a vacuum; it is filled with compressed gas. Usually it is sulphur hexofluoride. The losses of a system including compressed gas-insulated transmission are rather low; they are considerably lower than those of cable transmission. Besides, unlike cables, compressed gas-insulated transmission system can be designed for ultra-high frequencies. The next advantage is that there is no external electric field in the system. This type of transmission lines can transmit power over larger distances than cable lines.
The comparative simplicity of construction makes the cost of gas-insulated transmission considerably lower than that of cable lines.
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fluoride -
hexode -
V. Translate the following sentences, pay attention to the polysemantic meanings of words in bold type.
1. There are clock that mark time with an accuracy of one second per 300 years. 2. He gets only good and excellent marks for his answers at all exams. 3. You must review grammar rules regularly. 4. You English instructor will return your paper with a review. 5. Let us centre our attention on the research. 6. The consultation centre of the Institute is not far away from my job. 7. To pass an exam by Physics you must give the subject much attention and time. 8. When you come to the place you must show your pass at the entrance.
VI. Translate the following words, pay attention to the meaning of prefixes "over-, inter-, under-".
| over- to overestimate to overcharge to overvalue to overheat to overcool to overload to overpay |
| under- to underestimate to undercharge to undervalue to undergo to understand underground |
inter-
to inter charge
to interact
to intermix
international
interstellar
the interchange
interconnection
GRAMMAR REFERENCES
(THE INFINITIVE)
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receive , not to send .
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| Active | Passive | |
| Indefinite | to do | to be done |
| Continuous | to be doing | _ |
| Perfect | to have done | to have been |
| Perfect Continuous | to have been doing |
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Continuous Infinitive , - .
Perfect Infinitive , , -.
Perfect Continuous Infinitive , , -.
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She wanted to be invited to the party.
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design plans of new building is the work of an architect.
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His duty was to observe the operation of this system.
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The professor asked the student to define the unit of resistance more accurately.
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Pyrometers are used to detect the heat objects radiate.
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A thermometer is an instrument to show the temperature.
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Examinations were to have been passed at the beginning of June.
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1. The Objective Infinitive Complex (Complex Object) ( ).
2. The Subjective Infinitive Complex (Complex Subject) ( ).
3. Absolute Infinitive Complex .
Infinitive Construction with the Preposition "for" for.
6.
LEXICAL REFERENCES
(THE POLYSEMY)
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