Transmission of electrical energy

The process of moving electric power is called electric energy transfer. This process usually includes the transmission of electrical energy from the generator or producer to the distribution stations near cities or centers of industrial concentration, and henceforth means the delivery of electrical energy to consumers within the scope of electrical energy distribution. The transfer of electric energy allows us to use electric energy simply and without accepting the cost of transporting fuels, as well as separating from the pollution produced by burning fuels in the power plant. In many cases, it is impossible to transfer energy sources such as wind or water from dams, and the only possible way is to transfer electrical energy.

Due to the large amount of power in question, transformers work at more or less high voltages (110 kV or more). Electrical energy is usually transmitted over long distances by air lines. Underground lines are used only in densely populated urban areas, and this is due to the high cost of setting up and maintaining, as well as generating additional reactive power in such lines.

Today, voltage transmission lines mostly include lines with a voltage higher than 110 kV. Lower voltages, such as 33 or 66 kV, are rarely used to power lighting loads on long routes. Voltages below 33 kV are usually used for electrical power distribution. Voltages higher than 230 kV are referred to as "extra high voltage" because most of the equipment required in these voltages are completely different from low voltage equipment.

History

In the early years of using electric energy, power transmission was done with the same voltage as the consumers, and this was due to the use of electric power in the form of DC, because at that time there was no way to increase the DC voltage, and because different types of consumers such as lamps s or motors needed different voltages, for each one a separate generator had to be used, which eliminates the possibility of using a large network to feed all consumers.

At the meeting of the AIEE group on May 16, 1888, Nikola Tesla presented an article called "A new system of alternating motors and transformers" and explained the advantages of using this system. Some time later, "Westinghouse" company proposed to build the first alternating current system.

By using the transformer, it was possible to connect the generators to the high voltage transmission lines and also the possibility to connect the high voltage lines to the local distribution networks. By choosing a suitable frequency, it was possible to feed all kinds of loads, including lighting and motors. The rotary converter and later mercury arc lamps and other current rectifiers made it possible to connect DC consumers to the grid using a type of rectifier.

Even consumers with different frequencies could be connected to the grid using rotary converters. By using centralized power plants to produce electricity, it was also possible to save money through mass production, and the load factor in each power plant made it possible to produce with higher efficiency, so that it was possible to use electricity at a lower price for consumers. . In this way, it became possible to create a large network to feed different types of consumers.

By using several times larger power plants connected to a large area, the cost of generating electricity was reduced and it became possible to use higher efficiency power plants that could feed different loads. Also, in this way, the stability of electricity production increased and the cost of investment in this sector decreased, and finally, it was possible to use remote energy sources such as hydroelectric power plants or coal from distant mines, without the need to pay for fuel transportation. provided

In early transmission lines, pin-and-sleeve insulators were used. These insulators are similar to those used today for overhead telephone lines. The use of these insulators was limited because they could be used up to 40 kV. In 1907, the invention of plate insulators by Harold W. Buck of the Niagara Falls Power Company made it possible to use insulators at higher voltages, so that the first transmission line for high amounts of electrical energy in the United States between the Falls Hydroelectric Plant Niagara and "Buffalo" were born in New York. A statue of Nikola Tesla now stands next to Niagara Falls in recognition of his contribution to the transmission of electrical energy.

During the 20th century, the transmitted voltage gradually increased. In 1914, fifty-five transmission lines with a voltage of more than 70 kV were in use, among which the highest transmission voltage was 150 kV. The first three-phase transmission line with a voltage of 110 kilowatts was launched in Germany between Lachhammer and Riza in 1912. On April 17th, 1929, the first 220 kV transmission line was put into operation in Germany, passing through four cities on its way. In this line, masts were built to increase the possible voltage up to 380 kV. The first 380 kV transmission line was built in 1957, ten years later, in 1967, the first transmission line with a very high voltage of 735 kV was built.

Finally, in 1982, a transmission line with a voltage of 1200 kV was built in the Soviet Union; This voltage is the most used voltage in transmission lines in the world.

The reason for using such a voltage in the Soviet Union was the vastness of this country compared to the density of cities.

The high acceleration of industrialization in the 20th century quickly turned electrical energy into one of the most important economic infrastructures in industrialized countries. In this way, local generators and small distribution networks quickly gave way to large energy production and transmission networks. With the beginning of the First World War, the acceleration of these changes increased and the governments quickly started to build large power plants to produce the electrical energy needed in the weapons factories. Later, these power plants were used to feed urban consumers.

Energy transfer on large scales

Engineers designing transmission lines increase the amount of transmitted power as much as possible in the calculations related to the design of these lines, of course, considerations and limitations such as network safety, the possibility of network expansion, route restrictions, etc. are taken into account in the design of networks.

The efficiency of transmission lines increases as the voltage increases, as this decreases the current. In large-scale power transmission, efficiency is very important, and losses greater than the standard can cause a lot of damage to a network or even make its use uneconomical, and this increases the importance of calculations and standards related to losses; Therefore, transmission line losses are one of the main parameters of network calculations.

In general, the electrical energy network consists of a power plant or producer, circuit or transmission network and voltage change stations. Power is usually transferred along transmission lines as three-phase AC. Using DC current for transmission requires expensive equipment to convert the type of current. Of course, the use of this equipment can be justified for some large projects. The use of electrical energy in the form of single-phase AC is only used in distribution to domestic and office consumers, because in industries, due to the use of three-phase motors, the use of electrical energy in the form of three phases is more economical. Of course, the use of systems with more than three phases is also common for some special applications.