The world around us is hard to imagine without electricity, which has penetrated all areas of modern life. This type of energy is used for lighting, rotation of electric motors, various electronic devices are powered from it, etc. Itself the electrical equipment forms a complex technical system, which must necessarily ensure the generation of electric current as energy at power plants, its delivery directly to the point of connection of the consumer and subsequent transformation into the desired form work.
DC and AC
To generate electric current, an external energy source is required, the functions of which can be performed by:
- heat from the combustion of coal, oil and gas;
- the flow of water from a reservoir or created by tides;
- wind;
- solar radiation;
- chemical processes in the battery.
Further, in one way or another, this energy is converted into current, which is transmitted through wires to the connection point of the receiver and is used there to perform useful work.
The current itself can be either constant or alternating. Alternating current usually has a sinusoidal character, which is due to the nature of its receipt as a result of the rotational movement of the generator shaft, Figure 1.
Advantages and disadvantages of DC and AC networks
DC networks in the early stages of the development of electrical engineering favorably differed in the simplicity of creating electric motors working from them. This advantage was lost immediately after the invention of the polyphase electric motor in 1882.
In terms of electric lighting on incandescent lamps, AC and DC voltage are equivalent.
From the point of view of the transmission of electricity from the place of its generation to the consumption of the AC network turned out to be out of competition immediately after the invention and development of the design of the power transformer.
The latter was associated with electricity losses. For safety reasons, the consumer requires a relatively low voltage, while losses during transportation are reduced when switching to high voltage. Voltage change in high-current DC networks is still not solved by simple means, while in AC networks for this, it is enough to install two transformers of the corresponding power at the ends of the line, picture 2.
History of development of AC and DC networks
For the first time mass commercial use in the late 70s. 19th century received three-wire DC networks (+/- 110 V and 0 V), which were created on equipment of the Edison Electric Edison Electric Light company (currently part of General Electric "). It was with them that the first samples of incandescent lamps were fed, Figure 3.
The industrial production of suitable for mass use electrical equipment of alternating current, created by Nikola Tesla, was mastered by Westinghouse ten years later. Despite such a large time lag due to the noticeably better operational parameters of the power grid, it quickly ousted its competitor based on it. Already at the end of the 20s. XX century in the United States, DC networks were no longer used at newly created facilities. However, the last one was decommissioned only in 2007.