Electric Lines and Their Efficiency

Put down the nouns corresponding to these verbs. Follow the model.

Model: to act - action

to ignore -__________________ to produce -____________________

to depend -_________________ to use -_________________

to cost -__________________ to lose -____________________

4. Translate into Russian:

a. line efficiency

voltage loss

power station _______________________

b. interdependent values _______________________

interconnected sources _______________________

changing power efficiency _______________________

c. exceedingly high power losses _______________________

exceedingly inefficient energy sources 1

d. One can ignore these exceedingly low power losses.

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One should take into consideration the interdependence of these values^

One should not ignore the high cost of these installations.

wiring are commonly produced of copper and aluminium. Aluminium is widely used nowadays due to its low cost. Copper is also widely used in electrical engineering but its cost is much higher.

Wires connecting the components of various installations may be in­sulated. They may also be used without insulation. Since in short lengths of wire power loss is exceedingly low one can ignore it. In long wires (longer than 10 m), power loss cannot be ignored since it is rather high. Power loss in a line should not exceed a definite value. If this value is exceeded the line becomes inefficient.

One should know that the efficiency of a line is not constant - it may change. The value of the line efficiency depends on the load: the greater the load the lower is the line efficiency. At voltage losses of 2 to 5 per cent the efficiency of a line is 98-95 per cent. Protecting devices, fuses and relays are used to protect the circuit against overcurrents and short-circuits.

5. Complete the sentences using the correct variant:

1.	Aluminium is used due to its	a) high cost. b) low cost and high efficiency.
2.	Cross-section of different conductors	a) varies. b) is the same.
3.	Power loss can be ignored	a) in short wires. b) in long wires.
4.	A definite value of loss	a) can be exceeded. b) should not be exceeded.
5.	Electric lines nowadays are	a) efficient. b) inefficient.
6.	Installations are protected	a) by switches. b) by fuses.

6. Complete these sentences using while. Follow the model on page 13:

1. The cost of aluminium is comparatively low while....

2. In a short length of wire power loss is extremely low while....

3. The greater the load the lower is the efficiency of the line....

Wires are used to deliver electric power and to interconnect differed components of electrical installations. Conductors used for electr|

Answer these questions:

1. Why is aluminium widely used nowadays?

2. Is its cost very low or comparatively low?

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1796 - 6S -

3. What is the cross-section of copper conductors? 4. May one ignore power loss in short wire? Why? 5. What does the efficiency of a line depend on? 6. What are fuses used for? 7. When does a line become inefficient? Think of three questions about this extract and put them to your groupmate. con'sumer - потребитель; relation - отношение When electric energy is produced at the power station, it is to be trans­mitted over electric wires to the consumer. Wire conductors offer resis* tance to the current flow; the longer the wire, the greater is its resistance to the current flow. Accordingly, the higher the offered resistance, the greater are the heating losses in the wire.

a) Cover the right column and read the English words. Translate them into Russian and check your translation. b) Cover the left column and translate the Russian words back into English.

area

distance

network

support

cord

bus

enterprise

to term

to divide

to support

to distribute

accordingly

as to

long distance

length of transmission lines

power consumption

distribution centre

citv area

.'eanaj площадь, область

расстояние

сеть электролиний

опора, мачта

провод

шина ['entapraiz] предприятие

[di'vaid)

называть, именовать

делить, разделять

поддерживать

распределять

соответственно

... что касается;... что до!

большое расстояние

длина линий передачи

потребление энергии

распределительный центр

район городской застройки

2. Put down the Russian for:

interdependent city areas

interacting underground lines_____________________________

interconnected overhead lines_________________________________

transmitting power lines

transmission and distribution lines _______________

overhead lines

step-down transformer

indoor lines

underground lines__________________________________________

Transmission Lines

A power system is an interconnection of electric power stations by high voltage power transmission lines. Nowadays the electricity is trans­mitted over long distances and the length of transmitting power lines varies from area to area.

A wire system is termed a power line in case it has no parallel branches and a power network in case it has parallel branches.

According to their functions, power lines and networks are subdivided into transmission and distribution lines.

Transmission lines serve to deliver power from a station to distribu­tion centres. Distribution lines deliver power from distribution centres to the loads.

Lines are also classed into: 1) overhead; 2) indoor; 3) cable (under­ground).

Overhead lines include line conductors, insulators, and supports. The conductors are connected to the insulators, and these are connected to the supports. The greater the resistance, the higher are the heating losses in the conducting wires. In order to reduce the losses, a step-down trans­former can be used.

Indoor lines include conductors, cords, and buses. The conductor may include one wire or a combination of wires not insulated from one an­other. They deliver electric current to the consumers.

As to underground lines, they are used in city areas. Accordingly, they are used in cities and towns, and in the areas of industrial enterprises.

3* Complete these sentences using the correct variant.

1. Electric power is transmitted a) by electric lines.

b) by power networks.

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5*

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2. Lines are divided into

3. An overhead line includes

4. The insulators are connected

5. Conductors consist of

6. Underground lines are used

a) overhead and underground.

b) overhead, indoor and underground.

a) conductors and supports.

b) conductors, insulators and supports.

a) to the buses.

b) to the supports.

a) bare wire.

b) insulated wire.

a) in cities.

b) in areas of enterprises.

c) in agricultural areas.

danger	I'demdja]	опасность
strength	[strerj9]	сила
earth	[з:0]	заземление, земля
ground		земля, почва
dead	[ded]	выключенный
dangerous	I'deir^ras]	опасный
strong		сильный, яркий (о свете)
to save		спасать
to disappear		исчезать
to appear		появляться
live	llaiv]	под напряжением
4ГУ		сухой
wet		сырой, мокрый

4. Complete the sentences using while or as to. Follow the model on page

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