We know that to this day it has not yet been possible to transmit electrical energy through the air, such as a tesla coil for example, at least not in a viable way. Therefore, the best way to transmit all the energy generated by any type of plant is through electric power networks.
Electricity networks are extremely important for energy to reach consumers, so we will explain what electrical networks really are and why they are so important. Come on!
The electrical energy that leaves the power plants and electric generators is transported through overhead cables, covered by insulating layers and fixed in huge metal towers, where we can define this whole set of cables and towers as a network for the transmission of electrical energy.
In this power distribution system, electric power transmitters are usually managed with high voltage, but they can also be networks with lower voltage levels within the concessionaires themselves. These different voltage levels throughout this process serve to ensure that energy reaches consumers in the best possible way.
In addition to the cables and transmission towers, other important elements of the transmission networks are insulators, which can be made of glass or porcelain, which surround and support the cables, preventing electrical discharges along the way, preventing accidents and minimizing costs of losses, for example.
The electricity distribution power networks, in addition to the transmission lines, are also composed of transformation substations, composed of transformers, protection and control equipment.
The transmission lines are basically made up of metallic conducting wires suspended in metal towers, by means of ceramic insulators or other highly insulating materials.
The transmission lines extend over long distances, connecting generating plants to large consumers, those who purchase energy at high voltage, such as factories, mining companies and energy distribution companies, which are responsible for bringing energy to smaller consumers.
As the power systems are three-phase, there are generally three sets of cables located in the transmission towers, and these cables are accompanied by a taller cable, located at the top of the tower, this is the lightning rod, also called the cable guard.
Transmission lines in Brazil are classified according to their operating voltage level. For each voltage range, there is a code that represents a whole set of transmission lines of the same class. Are they:
- A1 – Supply voltage equal to or greater than 230 kV
- A2 – Supply voltage between 88 kV and 138 kV
- A3 – Supply voltage 69 kV
The transmission substations are located at the connection points with generators, consumers and energy distribution companies. At the connection points with generators, the function of the substations is to raise the voltage level of the electricity generated to hundreds of thousands of Volts, which brings certain advantages such as reducing the electric current, reducing the cable sections, reducing costs and mainly losses, in addition to many other advantages.
At points of connection with consumers or energy distributors, the function of transmission substations is to lower the voltage levels that were raised at points of connection with generators.
The transmission substation has sectioning equipment for maintenance maneuvers, as well as circuit breake and system measurement and protection equipment, such as voltage, current and lightning arresters.
The distribution networks are composed of low, medium and high voltage lines, and transmission lines that have a voltage equal to or greater than 230 kV are called the basic network.
Although some electric power transmitters have lines with a voltage below 230 kV, most transmission lines with a voltage between 69 kV and 138 kV are the responsibility of the energy distribution companies and are known in the sector as subtransmission lines.
The energy distributors operate medium and low voltage lines, also called primary and secondary networks, respectively. The medium voltage lines have an electrical voltage between 2.3 kV and 44 kV, and can be easily seen on streets and avenues in large cities, being generally composed of three overhead cables, supported by wooden crosspieces on concrete poles.
On the other hand, low voltage networks have a voltage that can vary between 110 and 440V depending on the region, they are affixed to the same concrete posts that support medium voltage networks, located at a lower height.
Types of distribution networks
There are four types of electricity distribution networks, conventional aerial distribution network, compact aerial distribution network, isolated aerial distribution network and underground distribution network, where:
- Conventional Aerial Distribution Network: It is the most common type of electrical network in Brazil, where electrical conductors are not insulated and that is why these networks are more vulnerable to the occurrence of a short circuit.
- Compact Aerial Distribution Network: Compact networks are much more protected than conventional networks, not only because the conductors have an insulation layer, but because the network itself occupies a smaller space, reducing the number of disturbances.
- Isolated Aerial Distribution Network: This type of network is well protected, as the conductors are covered with sufficient insulation to be braided, it is generally more expensive and used in special conditions.
- Underground Distribution Network: The underground network is the one that provides the highest level of reliability and offers the best aesthetic result, as the networks are buried, without the possibility of visual pollution. Despite the mentioned advantages, underground networks compared to other types of networks, they are much more expensive, being common only in denser regions or where there are restrictions for the installation of overhead networks.