Do you know what an electrical substation is? What'a up Engineering lovers, my name is Igor Felipe and today we are going to talk about electrical substations. I'm sure you've seen this type of installation or heard about it on the news, but what does it do?
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Well, let's get going. When you plug an electrical device into an outlet, do you know where the electricity comes from? The simple answer is a power generating station, also known as a power plant, usually somewhere far away.
But the reality is much more complicated than that. Generation is only the first of many steps that electrical energy takes in its almost instantaneous journey from production to consumption. As simple as it may be to imagine, the electrical system is not just a series of interconnected wires to which power generation units and users connect.
In reality, electricity normally goes through a series of stages on its way from generation to consumption, these parts being: the generation or production of electricity; transmission or movement of this electricity from generating plants to populated areas; and distribution or delivery of electricity to each individual customer. If you consider the electrical network to be a gigantic machine, substations are the elements that connect the various components. Substations serve several specific purposes in the electrical system.
These functions depend on which parts of the power grid are being connected together and the types, numbers and reliability requirements of consumers. And the first and generally the simplest of these functions is the sectioning of electrical circuits. Think of a big city, you can have a series of transmission lines coming in to feed the loads in that city.
Let's suppose we have a problem with any of these transmission lines. In this case, we must have the ability to isolate this transmission line from the system, to keep the electrical circuit active, through another transmission line. The equipment that does this circuit isolation function is called a switch disconnector.
In addition to the function of sectioning electrical circuits, substations have the function of transforming voltage levels. The substations connected between the generation and transmission stages have the function of raising the voltage levels. Normally power plants generate energy at a low voltage level and these voltages must be high in order to be transmitted.
Depending on a number of factors, these voltages can vary between 138, 230, 500 and 750 thousand volts Substations connected between the transmission and distribution stages have the opposite function. They serve to reduce these voltage values to the distribution voltage values, which, in most Brazilian cities, is 13800 volts. This energy transformation is done by equipment called a transformer.
A transformer is an extremely simple device that depends on alternating current to function. It consists of two adjacent coils. As the voltage in a coil changes, it creates a magnetic field.
This field is coupled to the other coil, inducing voltage. The ratio of a transformer's voltages has to do with the number of loops on each coil. The induced voltage will be proportional to the ratio of the loops.
For example, if the transmission side of a transformer has 1000 loops while the distribution has 100, the voltage on the distribution side will be 10 times less. And that simple fact makes it possible to increase or decrease the voltage as needed. The other important function of substations is the protection of electrical circuits.
They must be able to prevent faults, such as short circuits that occur in the transmission lines, from reaching our homes. And for that, the substations have a series of devices to analyze the current and voltage levels in their circuits and determine whether to interrupt a specific circuit. The simplest way to protect against this type of failure is with a fuse, a device that physically burns when it reaches a certain limit.
Fuses are extremely simple and do not require much maintenance, but they do have some disadvantages as well. They are for single use only and cannot be used to interrupt the current in all types of failures. For these cases, circuit breakers are a class of devices that perform functions similar to fuses, but provide more sophistication to deal with a wide variety of failures.
Circuit breakers are, in a way, the same as we have inside our homes, but on a much larger scale. Circuit breakers need to be carefully designed to interrupt huge voltages and currents without damage. As soon as the contacts inside a circuit breaker are separated from each other, electrical arcs can occur.
Electric arcs happen when air, which is normally an insulator, conducts electricity. This arc must be extinguished as soon as possible to avoid damage to the circuit breaker or unsafe conditions for workers. For lower voltages, circuit breakers can be located in a vacuum-sealed container to avoid conducting electricity in the air between the contacts.
For higher voltages, circuit breakers are often submerged in tanks filled with non-conductive oil, or dense dielectric gas. These circuit breakers give network operators more control over how and when the current is interrupted. Not all faults are the same, and operators sometimes know about a disturbance and can trip circuit breakers in advance to prevent cascading faults.
Many failures are temporary, like lightning or branches falling on conductors. Or they can also be more complex faults, such as when the conductors of a transmission line come into contact with the ground, for example. The analysis of these currents is done by electronic protection devices, called protection relays.
These electronic equipment receive current and voltage signals directly from the system and analyze the performance of these systems based on pre-defined adjusts for each type of circuit. All the equipment we mentioned, transformers, switch disconnectors and circuit breakers do not work as isolated units, and to make the connection between these equipment we use the busbars. Busbars are rigid copper bars that are sized to conduct large amounts of electrical currents.
The bus layout is a critical part of the design of any substation because it can have a major impact on overall reliability. These buses are supported by insulators. In addition to the support function of the bus structure, it has the function of isolating the electric current between the bus and the ground.
After all, we don't want a high voltage conductor to accidentally touch the ground. This is just a video giving an overview of substations and their main equipment, but we still have a number of important equipment that we can talk about. If you want a video detailing the substations and their equipment, leave it here in the comments.
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