Electric Power Consumers and Power Systems

An electric power consumer is an enterprise utilizing electric power. Its operating characteristics vary during the hours of day, days and nights, days of week and seasons.

All electric power consumers are divided into groups with common load characteristics. The first group includes different municipal consumers with a predominant lighting load: dwelling houses, hospitals, theatres, street lighting systems, etc. The second group includes industrial consumers with a predominant power load (electric motors): industrial plants, mines, etc. The third group includes transport, for example, electrified railways. The fourth group consists of agricultural consumers.

The operating load conditions of each group are determined by the load graph. The load graph shows the consumption of power during different periods of time (day, month, year). On the load graph the time of the maximum loads and minimum loads is given.

Large industrial areas with cities are supplied from electric networks fed by electric power plants. They are interconnected for operation in parallel and located in different parts of the given area. They may include some large thermal and hydroelectric power plants.

The sum total of the electric power plants, the networks that interconnect them and the power utilizing devices of the consumers, is called a power system. All the components of a power system are interrelated by the common processes of protection, distribution, and consumption of both electric and heat power.

 

Text 5

Difference between A.C. and D.C.

A direct current (D.C.) flows continuously through a conducting circuit in one direction only, although it may not be steady so far as magnitude is concerned. It is unidirectional in character. An alternating current (A.C.), on the other hand, continually reverses in direction, as its name implies. Starting from zero, it grows in one direction, reaches a maximum, drops to zero again, after which it rises in the opposite direction, reaches a maximum, again decreasing to zero. It is thus continually changing in magnitude as well as direction, and this continual change causes certain effects of far-reaching importance.

It can be shown that high voltages are desirable for the economic transmission of a given amount of electric power. Take, for example, the transmission of 1000 kW. If the transmission voltage is 100 volts the current must be 10,000 amperes, but if the transmission voltage is 10,000 volts the current is only 100 amperes. The cross-section of the cables transmitting the power is determined by the current to be carried, and so in the former case the cables would need to be very much larger than in the latter case. It is true that the high-voltage cable would need to have more insulation, but even so, it would be very much cheaper than the larger low-voltage cable. A high voltage is therefore essential for the economic transmission of electric power. Again, a.c. generators can be designed and built for much higher voltages than can d.c. generators, the voltage of the latter being limited by the problem of sparking at the commutator, a component which is absent in the a.c. generator. Then there is the most important factor that it is easy to transform a.c. power from one voltage to another by means of the transformer, an operation that is denied to the d.c. system.

The transformer also enables the voltage to be stepped down at the receiving end of the transmission line to values which can readily be used by the various consumers. If necessary, it can be converted to the d.c. form for actual use, although this is not often necessary.

There are certain processes for which D.C. is either essential or at any rate desirable but the utilization of electric power in the a.c. form is growing steadily. At the present day, by far the greater part of the generation, transmission, and utilization of electric power is carried out by means of A.C.

References

1. Бахчисарайцева М.Э., Каширина В.А., Антипова А.Ф. Пособие по английскому языку для старших курсов энергетических вузов. – М.: Высшая школа, 1983. - 159 c.

2. Иванова К. А., Английский язык для студентов-электротехников. –Ленинград, 1983. - 168 с.

3. Английский язык. Профессионально-ориентированный курс: учебное пособие / Т.Б. Лысунец, М.В. Нетесова, 2012. – 120 с.

4. Encyclopedia: Energy Education. Режим доступа: http://energyeducation.ca/encyclopedia/Energy_loss

5. IMIA-WGP-6910-Transmission-and-Distribution-Lines20_05_2010-3.pdf https://www.imia.com/wp-content/uploads/2013/05/IMIA-WGP-6910-Transmission-and-Distribution-Lines20_05_2010-3.pdf

 

 Contents

 

1.	Transmission networks ……………………………………………………..	4
2.	Electric Power Distribution…………………………………………………	5
3.	Electromagnetic field……………………………………………………….	8
4.	Non-conventional renewable energy sources………………………………	9
5.	Energy losses……………………………………………………………….	11
6.	For additional reading………………………………………………………	14
	Text 1.Electrical measurements……………………………………………	14
	Text 2. Conductors and insulators………………………………………….	15
	Text 3. Substations………………………………………………………….	16
	Text 4.Electric Power Consumers and Power Systems……………………	17
	Text 5.Difference between A.C. and D.C………………………………….	17
7. 8.	References…………………………………………………………………...   Contents…………………………………………………………………….	19 20