The distribution network in the power system
The power system is divided into three clearly differentiated parts: generation systems, consumers, and the distribution network. In this post, we’re going to focus on the distribution network.
Table of contents
The distribution network as part of the power system
How does the power transmission grid work?
Cables that bring light to your home
Key aspects of power system distribution
The transmission grid makes it possible to carry energy from the points of generation (conventional generation systems or renewable energy systems) to the centres of consumption (your home). These distances are covered in sections that operate at different voltages: after high voltage, high-power consumers receive energy at medium voltage and, finally, as we get closer to cities, at low voltage. In other words, your home is not connected directly to a nuclear power plant, but to lower-voltage substations so that you can receive electricity at an appropriate voltage. This transmission is a fundamental part of the power system. The power system’s distribution network is the part of the electrical grid that delivers power from the transmission system to end users.
Okay, that makes sense so far, but how do we actually step those voltages down?
Stages of electrical power transmission and distribution
What is a transformer?
To step voltages down, we use substations, whose key components are transformers. Transformers work like generators and motors, only they don’t move.
The medium-voltage distribution network is made up of towers similar to high-voltage ones, but smaller. These towers bring the power to the outskirts of cities, where it then connects to the black bundled cable that actually reaches your home.
Stages of electricity transmission
So, the transmission of electrical energy can be broken down into several stages:
1) Power plants or generating stations
The first step in transmission is the power plants or stations where electricity is generated. The energy source can vary substantially. Electricity is usually generated at between 10 and 20 kilovolts, that is, between 10,000 and 20,000 volts. To reach cities or industrial facilities, it may have to travel long distances, so the voltage needs to be increased significantly.
2) Transmission substation
The next step is the transmission substation, which raises the voltage using a step-up transformer to reduce cable size and electrical losses. The amount of voltage increase depends on the distance it will have to travel and on the type of facilities that will ultimately be supplied. It typically ranges from 200,000 to 380,000 volts, that is, from 200 to 380 kilovolts. The higher the towers, the higher the voltage they carry.
3) Sub-transmission stage
The electrical energy is then distributed in multiple directions to the most appropriate sub-transmission stations. The sub-transmission station is located closer to the end user and, as a result, the voltage is reduced by a step-down transformer to a suitable level. The voltage is reduced to around 60,000 volts.
4) Distribution substation
In the fourth stage, electricity is sent to the distribution substation, where the voltage is reduced by step-down transformers to useful levels. The electrical energy is then distributed to homes (230–240 volts) and to facilities (normally 400 volts).
5) Local transformers near users
At each household, or close to it, there are transformers that adjust the voltage to the appropriate level for use. For example, a large industrial plant will use its own step-down transformers on site to produce the different voltage levels required within the facility.
Conductors in the power distribution system
When it comes to wiring or conductors, these are one of the most important parts of power distribution, since they carry energy from its source to its destination. The cables that cross the country are relatively small in diameter compared to the very high voltages they carry. This is due to the current: the lower the current, the cheaper and more efficient the transmission of energy is.
To answer the question “how is electricity distributed?”, remember that its distribution needs to be divided into several stages before it reaches our homes.
The next time you see high-voltage towers with their black cables, remember that thanks to them the power system works properly and allows us to enjoy electricity in our homes. Just don’t touch them!