In this blog post, we’ll examine the process by which electricity is generated and supplied to homes, focusing on the principles behind how household lights turn on.
Electricity Generation and the Characteristics of Alternating Current
Electricity is now an energy source we can hardly do without for even a single day. When a power outage occurs, people experience significant inconvenience and, depending on the situation, may even feel anxious. In fact, due to seasonal factors and increased industrial activity, electricity demand has risen significantly recently, making the management of electricity supply and demand even more critical. As such, electricity plays a vital role in our daily lives today, and its importance is expected to grow even further in the future. So, what process does electricity go through to reach our homes? The process begins with the generation of electricity.
Although electricity is a single form of energy, various energy sources are required to produce it. Currently, power plants generate electricity using a variety of energy sources, including not only oil but also natural gas, coal, nuclear power, hydropower, wind power, and solar power. The electricity produced in this way is supplied to households. Before explaining the next step in the process, let’s first examine a basic concept in physics: electric current. Electric current can be broadly divided into direct current (DC) and alternating current (AC). Current that flows in only one direction is called direct current, while current whose direction changes periodically is called alternating current. Generally, direct current requires power conversion equipment for long-distance transmission; however, with recent advancements in high-voltage direct current (HVDC) technology, it is now being utilized for long-distance transmission as well. Nevertheless, the typical power grid that supplies electricity to households operates primarily on alternating current, which facilitates power generation and transformation. Consequently, most of the electricity produced at power plants and supplied to households and industrial sites in South Korea is alternating current.
The Process of Voltage Transformation and Transmission
Now, let’s examine how electricity is supplied from power plants that use AC to our homes. The process of delivering electricity to homes consists of three main stages.
First is “voltage transformation.” When electricity generated at a power plant travels long distances to homes, energy is lost due to resistance in the transmission lines. To explain this simply, let’s compare the transmission lines and electricity to a water pipe with small holes drilled at regular intervals and the water flowing through it. If there are holes in the water pipe, the amount of water reaching its destination will be less than the amount originally sent. To ensure the required amount reaches the destination, more water must be sent from the start. The same principle applies to electricity. However, in practice, voltage is increased to transmit the same amount of power using a lower current. Since a lower current significantly reduces power losses in transmission lines, this is highly advantageous for long-distance transmission. Therefore, power plants use transformers to step up the voltage. So, what is the principle behind voltage transformation?
Voltage transformation, as the term suggests, is the process of changing the magnitude of voltage. Transformers are essential components in modern power plants and power grids. The core principle of a transformer is the phenomenon of electromagnetic induction. Electromagnetic induction refers to the phenomenon in which a magnetic field generated by current flowing through a conductor changes over time, thereby inducing a voltage in another conductor. When the current increases or decreases, the magnetic field changes accordingly, and this changing magnetic field affects an adjacent coil, generating a voltage. The magnitude of this voltage varies depending on the ratio of the number of turns in the coils. Transformers utilize precisely this principle to step up voltage to higher levels or step it down to lower levels.
After the voltage is stepped up in this way, the intermediate process of “power transmission”—which delivers electricity to individual households—takes place. Power transmission occurs through long conductors capable of carrying current. These conductors are the power lines commonly seen along roadsides or in mountainous areas. So why are power lines installed at such heights? The reason is related to the first step explained earlier. The voltage used for transmission is extremely high, reaching hundreds of thousands of volts. In South Korea, ultra-high-voltage transmission grids such as 154 kV, 345 kV, and 765 kV are commonly used. Since such high voltages are extremely dangerous to humans, power lines are installed on tall steel towers to ensure a safe distance.
Electricity Delivered to Homes
The final step is, once again, “transformation.” The reason for undergoing one more transformation is that the high voltage used for transmission is extremely dangerous to people. Therefore, at substations and distribution facilities, the high voltage is stepped down through several stages before being supplied to homes. Since typical households in South Korea are supplied with approximately 220V AC, the voltage that was raised for transmission is lowered to a safe level using transformers.
The electricity we use in our daily lives turns on the lights the moment we flip a switch. Seeing it turn on so quickly might give the impression that electricity is supplied in a very simple way. Some people even think that electricity is stored inside the walls and comes out immediately. However, as we’ve seen so far, electricity is supplied to homes through a process that is far more complex than one might think. Electricity generated at power plants is transformed into a high voltage suitable for transmission, travels long distances along transmission lines, and is then stepped down to a safe voltage before being delivered to each home. It is only through this three-step process—transformation, transmission, and transformation—that the lights we use every day can come on.
