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		Generation, Distribution, Use of Electric Current - Basic vocational knowledge (Institut für Berufliche Entwicklung, 141 p.)
			(introduction...)
			Preface
			1. Introduction
			2. General remarks on the demand for electric energy and on the natural resources available
			3. Ways of generation of electric energy
			4. Power transmission and distribution in power supply systems
			5. Lighting installations and power installations
			6. The use of electric current by the various groups of consumers (assignment)
			7. Measuring technology of checking electrotechnical installations and equipment and of permanently controlling the main parameters in operation (I, U, P, Wh, Q, )
			8. Protective, control and supervisory systems as important additional equipment for power installations

6. The use of electric current by the various groups of consumers (assignment)

This section does not deal with the current simply as dimensioning quantity but with the basic quantity for the consequences caused by the various consumers in the different networks, such as conduction losses with the specific conductor heating, voltage drops as well as electromagnetic effects on the immediate environment of the line system carrying the current. The current networks are either D.C. (direct current) or A.C. (alternating current) systems. A.C. systems may have different frequencies, such as 16 2/3 Hz, 50 Hz and 60 Hz to name only the most usual ones. The D.C. and A.C. voltage levels differ very much nationally and internationally with only a few equal international levels. In addition to the known A.C. voltage levels of 220 V. 380 V. 500 V and 600 V and D.C. voltage levels of 220 V, 440 V, 600 V, 850 V, there is a great number of other voltages. However, there is a move towards international standardization. The assignment of consumers is always to be seen in connection with the type of current concerned. Basically, four different effects of the electric current are used:

- heat effect (heating/cooling),
- light effect (lamps, projectors, tubes),
- magnetic effect (electromagnet, electric motor),
- chemical effect (accumulator, electrolysis, melting furnace).

A very low percentage of the electric energy generated by power stations can be stored in pumped storage power stations. Most of it is to be supplied to immediate consumption otherwise it will get lost. It is the task of the electric power industry to match the quantity of electric energy to be produced with the consumers demand for electric energy at any moment. This is done by switching on and off generators in the power plant. The available service energy is used by public, private, industrial, agricultural and cultural consumers.

Public consumers include:

- local traffic and long-distance traffic including industrial railways,
- street lighting including illumination of buildings, monuments and advertisement spaces,
- municipal water supply and disposal with all electrotechnical equipment, e.g. pumps, compressors, valves and gates,
- postal service including communications, broadcasting service and newspaper service.

Private consumers use electric energy primarily for

- illumination and cooking (lamps, stoves, ranges),
- washing (washing machines),
- cooling (refrigerators, freezers),
- heating (smoothing irons, hair dryers),
- entertainment (radios, TV sets, sound equipment),
- medical purposes (infrared radiators, solar radiators etc.),

The industrial consumers are the biggest group of consumers, such as

- transformers, electric motors, converters,
- annealing furnaces, melting furnaces, welding equipment,
- machines, controls, hoisting machinery,
- electroplating equipment, electrolysis,
- data processing equipment, information equipment, etc., etc.

The agriculture has also a high degree of electrification by

- pump and compressor equipment for irrigation and drainage,
- fodder preparation equipment, harvesters and threshers,
- milking machines, incubators,
- hot-house and greenhouse equipment (illumination, special radiators),
- air conditioning plants,
- grain draying plants.

The cultural sphere consumes a considerable quantity of electric energy for representation and scene illumination purposes. Air conditioning plants, hoisting machinery, transport equipment, water supply and disposal as well as advertisement are the main applications.

The afore-mentioned list indicates the variety of consumers within the individual groups of consumers. And, moreover, the habits, production cycles, national time cycles and climatic conditions as well as the relevant rates/charges have a decisive influence on the daily routine and load cycles within each group of consumers. The energy consumption is not continuously distributed over the whole day! So the consumers are also to be actively influenced to reasonably use electric energy!

Question for recapitulation and testing

1. Why is it difficult to calculate the consumer’s behaviour?