Electricity is becoming increasingly crucial in our lives. After all, it is through it that we accomplish various activities, whether for leisure or work. But you know how the electric power transmission is made so that it can reach the sockets of your home?
Countries with large territorial proportions, such as Brazil, generally keep big generators, such as hydroelectric dams, far from their consumers. To make the transmission of electricity is necessary a power transmission line, which travels thousands of kilometers to reach the cities.
The electric power transmission is divided into two stages: transmission to large centers, and distribution, which is used within urban centers. To know more about this subject and learn about the different forms of transmission, keep reading!
The war of currents
At the end of the 19th century, two important personalities participated in a debate on how electricity would be transmitted. On one side was Nikola Tesla, who along with George Westinghouse advocated the use of alternating current. On the other was Thomas Edison, who advocated the direct current.
Since Edison did not want to lose his monopoly, he advocated the direct current based on the risks that the alternating current could offer. On the other hand, Tesla supported the idea of alternating current, due to the ease in changing voltage levels, through the use of transformers.
The winner of this conflict was the alternating current, which over the years has become the most used in the transmission and distribution of electricity.
Alternating current transmission
Besides being an inventor, Tesla was also a physicist and an engineer, which helped him to create a theoretical basis for polyphasic systems of electric power transmission. Among his creations, the most used is the three-phase system, which consists of three current conductors of the same frequency and amplitude.
Another advantage of this power transmission system is the economy, since even with little conductive material, it can make the transmission with the same amount of energy. It is worth remembering that the three-phase generators are smaller and lighter than the single-phase generators, as they have greater efficiency in their bearings.
The three-phase motor is also smaller than its single-phase equivalent of the same power. It does not need a starting circuit, as it has a constant rotating field. Furthermore, the torque (lever) of the motors is consistent, generating fewer vibrations.
The three-phase rectifiers also have fewer ripples in the rectified voltage than the single-phase rectifiers. The power of this system is constant in a balanced system, while in the single-phase version it is canceled whenever the current or voltage passes through zero.
Direct current transmission
Since the 1970s, there is a movement to increase the development of power electronics. It was through these studies that the electricity transmission and distribution through high-voltage direct current (HVDC), became a possibility.
In order to make this electrical connection, some physical limits need to be taken into account, such as the transmission network for direct current electricity. This is because, through it, it is possible to use a high-voltage direct current in the transmission of large blocks of electrical energy.
The conversion between direct current and alternating current (used to raise the voltage and reduce the electric current), is carried out by means of rectifiers using high-voltage semiconductors.
The use of HVDC provides a series of advantages, such as decoupling systems and saving cables, opting for lighter structures. This transmission can be divided unipolar, with one conductor, or bipolar, with two conductors.
Electric power transmission in Brazil
In Brazil, there are two HVDC lines: Belo Monte and Itaipu, which bring energy from the north and south to the southeast. In the case of Itaipu, the plant supplies half of its energy to Paraguay (50 Hz) and the other half to Brazil (60 Hz). This operation helps to increase the safety and reliability of the electrical system.
However, not all energy is consumed by Paraguay, as its surplus is sold to Brazil. As this different frequency can not be directly incorporated into the SIN (Brazil’s National Integrated System), it is rectified in converter stations and transmitted in direct currents.
Arriving in the state of São Paulo, the frequency is converted back to alternating current, at 60 Hz. This process is done to increase safety and reliability in the entire electrical system.
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