Do you know how transmission lines work? What's Up Engineering Lovers, my name is Igor Felipe and today we are going to talk about the transmission lines. Well, in the past, power generation plants served only their local areas.
Electricity did not have to travel far between the places where it was created and where it was used. However, with the growth of urban areas spread across the country and as power plants grew and distanced from populated areas, there was a need to transport electricity efficiently over long distances. But with these long distances, some problems have arisen.
Connecting cities to power plants is not as simple as plugging an extension cord into an outlet. At the same time, generating electricity is a major undertaking, and can be considered as a complex industrial process that requires huge capital investments and ongoing costs of operation and maintenance. So we have a scenario where the power generating units are on one side and consumers are on the other.
And that is where the Transmission Lines come in. They are the solution to this problem, which is: connecting electricity generation to consumers, passing through isolated and sparsely populated areas. The transmission lines are designed to carry enormous amounts of energy, at very high voltages, over long distances.
To give you an idea, the largest transmission line in Brazil is 2539 km long, spanning 5 states and 81 cities. It transports the energy produced in Belo Monte, Pará to the southeast region. And to carry out this transport efficiently, there are several aspects to be taken into account.
The first one is the selection of drivers that we will use. For this selection, we must keep in mind a simple criterion, low resistivity, for this we use copper or aluminum conductors. After all, if we are going to take the trouble to produce electricity, we want to make sure that as much energy as possible reaches customers.
In addition, energy utilities only earn revenue from energy that reaches their home meter or an industry's energy meter. They are not compensated for the loss of energy in the grid, but even good conductors such as aluminum and copper have some resistance to the flow of electricity. You can even see this at home.
We can measure a small drop in voltage when a hairdryer or electric shower is turned on. In some older installations, if you use an incandescent lamp you will even notice that it slightly decreases its brightness. This is because there is a much more significant voltage drop when we connect loads that consume more electricity.
This voltage drop occurs because energy is being lost in the form of heat by the resistance of the wiring. In fact, this lost power is very easy to calculate: Power is the product of the current, which is the flow rate of the electric charge, and the voltage, which is the difference in the electric potential. For a simple conductor, we can use Ohm's law to show that the drop in voltage at one end of a wire is equal to the current times the resistance of the wire measured in ohms.
Substituting the voltage formula in the power formula, we find that the energy loss is equal to the current squared times the resistance. Therefore, if we want to reduce losses in a power line: We can reduce the resistance of the conductor by increasing its diameter or using more than one conductor wire. Or we can reduce the component that has the greatest impact, which is the current.
If we cut the current in half, you will cut the energy lost to a quarter due to the squared rise of the formula. Going back to Ohm's law, we can see that the only way to reduce the current and still get the same amount of energy is to increase the voltage. And this is done between the generation and transmission steps by the voltage-lifting substations.
In substations, they increase the voltage by decreasing the current. We have a video on the channel that talks about substations, and I'll leave a link at the end of this video. In these elevating substations, the transformers increase the voltage by up to 100,000 volts and sometimes much more before sending electricity on its way through the transmission lines.
This decreases the current in the lines, reducing wasted energy and ensuring that maximum energy reaches customers on the other side. But, this increased tension makes things much more dangerous. You can think of tension as the desire for electricity to flow.
High voltages mean that the energy really wants to move and will even find a way to flow through materials that we normally consider non-conductive, such as air. Engineers who design high voltage transmission lines must ensure that these lines are protected against electrical arcs and other hazards that come with high voltage. Most long-distance power lines do not use insulation around the conductors themselves, as the insulation in this case would have to be so thick that it would not be economical.
Instead, most of the insulation comes from insulators or simply by spacing the conductors together. Each phase is spaced far enough from the other two to avoid arcing between the phases. You may also notice that there are several different formats of support for these drivers.
And these formats will depend on the number of conductors being supported, voltage levels and requirements for electromagnetic induction between those conductors. The geometry of these transmission towers directly interferes with the mutual impedances of the conductors and the ability to conduct energy in the transmission line. It must also be tall enough to prevent any person or vehicle from getting close enough to the drivers to create an arc.
Electricity is transmitted in three phases, which is why you will see most of the transmission, conductors in groups of three. The conductors are connected to each tower by means of long insulators to maintain sufficient distance between energized lines and the tower. These insulators are usually made of ceramic discs.
These disks have a somewhat standardized insulating capacity , so an easy way to get a rough estimate of a transmission line voltage is to multiply the number of disks by 15. For example, a line that has 9 disks in each insulator, it is a 138 kV line. You will also often see smaller drivers running along the top of the transmission lines.
These static or shielded wires do not carry any current. They are there to protect the main conductors from lightning strikes, as well as to distribute short-circuit currents that can occur between a phase cable to the metal frame. But high voltage is not the only design challenge associated with transmission lines.
Conductor selection is an act of carefully balancing strength, endurance, resistivity and another very important factor: cost. The transmission lines are so long that even a small change in the diameter or type of material of the conductor can have an impact on the overall cost. So the design of these lines must find the perfect balance between technical and financial requirements.
And not only are cables expensive, but also structures, which must meet the requirements of mechanical stresses while being as light as possible. Each tower requires several foundations, which need to be designed specifically for each type of soil through which the transmission line passes. These foundations also represent high costs in the construction of a transmission line.
There is also the environmental and land challenge. A transmission line will necessarily pass through areas of environmental protection, forests of permanent preservation and different courses of streams and rivers. Therefore, the licensing process is complicated and requires many compensatory actions from companies required by environmental agencies.
The land tenure challenge lies in the owners' compensation agreements impacted by the transmission line layout. Legal embargoes in these cases can render ventures unfeasible and require a great deal of knowledge and legal and negotiation effort by companies that propose to build transmission lines. I will leave here two videos that I am sure will add on this subject.
The substation video is on the side too, so be sure to check it out. If you made it this far I will ask you to like this video and subscribe to the channel if you are not subscribed. That's it my friends, all the best and see you in the next video.
