Electrical grid
23 January 2025
The functioning of the electrical system
Let’s discover how the electrical system operates! From power generation and transmission through electrical grids to its distribution in homes and businesses via high-, medium-, and low-voltage grids. And all this while ensuring the efficient and safe flow of electricity.
The electrical system is complex. It enables the provision of electricity from generation sources to end users. This system requires four key activities to function properly: generation, transmission, distribution, and commercialisation.
To better understand the process, think of electricity as the journey bread takes from a bakery to your table. First, it is baked at the bakery (generation). Then, you purchase it from a store (retailer). It is transported by a lorry to various points of sale (transmission grid). Finally, it reaches the consumer through local delivery grids (distribution network).
How does the electrical system work?
The electrical system begins with the power generation process.
Electricity is made by converting energy resources such as solar, wind, gas, hydropower, or nuclear energy into electrical power. Once generated, transmission grids and distribution networks carry the electricity from power plants to substations and end users.
To visualise this, imagine an interconnected system of water wells: the wells represent power generators, while the channels that distribute the water resemble transmission and distribution lines. Using electricity is like drawing water from these wells.
Let’s break down the transmission grids and distribution networks to understand how they function!
Electricity generation
Power generation is the first step in supplying energy to the electrical grid. This process involves converting other energy sources into electricity, which takes place in power plants:
Depending on the energy source, power plants can include wind turbines (wind energy), photovoltaic or solar thermal plants (solar energy), hydroelectric plants (water energy), combined-cycle plants (gas), and nuclear plants (nuclear energy).
Each facility uses different methods to transform energy into electricity. For example, in a hydroelectric plant, flowing water spins turbines that generate electricity through a synchronous generator. In a solar photovoltaic plant, solar panels convert sunlight directly into electricity. After generation, electricity is transmitted through transmission grids and distribution networks toward the point of consumption.
Electricity transmission
Power transmission is the path electricity takes from large generation plants to major urban or industrial centres.
Subestación eléctrica.
Electricity is transported to large substations via overhead or underground cables made of copper or aluminium. It is transmitted at very high voltage to minimise energy losses over long distances.
In substations, electricity is decreased to a lower voltage using transformers and then connected to the distribution networrk. These substations can be either outdoor or housed within buildings, integrated into urban environments.
Electricity distribution
The distribution stage is essential for ensuring electricity reaches homes and businesses. As end users, we do not choose which substation supplies our electricity—this depends on our location and the real-time configuration of the distribution network.
The electricity grid must ensure supply continuity even when there are faults. It is monitored from a control centre to detect and resolve issues or unexpected incidents, such as those caused by extreme weather events. For instance, during Storm Bernard, substations were monitored and operated to guarantee electricity supply.
This means these control centres serve as the hub overseeing the transmission grid's proper operation 24/7, 365 days a year.
Therefore, the distribution company must ensure electricity reaches homes with quality and reliability under all circumstances, including extreme weather events. What is the difference between electricity retailers and distributors?
Distribution vs. marketing
Understanding the difference between distribution companies and electricity retailers can save time when signing up for an electricity contract:
Distributor: responsible for managing, operating, maintaining, and overseeing the distribution network. It ensures the safe and continuous delivery of electricity to users, besides repairing faults and managing the grid. Additionally, the distributor installs a smart meter that records electricity consumption. Although the company usually installs these devices, customers also have the option to install their meters. In the case of Endesa, the distributor is e-Distribución Redes Digitales.
Retailer: purchases electricity from generation plants and sells it to consumers. It offers tariffs and contracts tailored to consumer needs, issues bills, and provides customer service. In other words, it is the company consumers contract with for electricity supply and pay for the service, such as Endesa Energía.
Now that we know the electricity grid comprises different phases, let’s take a closer look at the components involved in electricity transmission and distribution.
The distribution network and its components
The distribution networks rely on electrical substations, facilities that connect high-voltage and extra-high-voltage lines. These substations reduce energy to different voltage levels so it can be transmitted at medium voltage to transformation centres.
Transformation centres are located near consumption points and are responsible for converting medium-voltage electricity into low-voltage so it can be delivered to end users.
The distribution networks have different voltage levels:
High-voltage lines operate between 36 kV and 145 kV and are used to transport electricity over long distances.
Medium-voltage lines operate between 1 kV and 35 kV to distribute electricity from substations to transformation centres.
Low-voltage lines operate below 1 kV, allowing electricity to reach the end user.
Furthermore, metering equipment records electricity consumption and generation at the supply point. To paint a picture, these devices function like a water meter measuring the amount of water used in a household.
The electrical system today
The electrical system faces significant challenges in adapting to modern demands. The transition to a more sustainable approach requires increased integration of renewable sources and modernisation of infrastructure.
So, what do distribution networks need in today’s context? Investments in infrastructure, the adoption of smart technologies, and the integration of energy storage systems are key areas for enhancing the resilience and efficiency of the electrical system.
Smart grids allow for greater flexibility and efficiency in managing electricity supply and demand. This way, they facilitate the integration of variable renewable sources such as solar and wind power.
The electricity grid is the backbone of modern life, powering everything from a single light bulb to entire cities. Its ability to transform and distribute energy not only keeps us connected but also drives the transition to a more sustainable future.
Moreover, distributed generation, a form of small-scale energy production, has become a key component of this new energy paradigm. The ability to generate electricity locally - largely due to the rise of self-consumption - reduces reliance on large power plants. It also minimises energy losses associated with long-distance transmission and distribution.
This decentralisation improves system efficiency while increasing resilience by diversifying energy sources.
However, distributed generation introduces new challenges for grid operation, as its production depends on highly variable weather conditions. This requires the distribution network’s configuration to continuously adapt to changes in generation and consumption, ensuring a stable, efficient, and high-quality supply.
Advanced technologies, such as demand response systems and smart load management, enable consumers and businesses to adjust their electricity usage in real time. Thus, they promote the more efficient use of energy resources.
Today, energy storage systems already allow excess energy to be stored during periods of high generation and released when demand is higher. This helps balance supply and demand, improving grid reliability.
In this context, the distributor becomes a Distribution System Operator (DSO), capable of actively managing consumers and generators to resolve incidents within its grid. DSOs must adapt their grid operation and planning processes to manage the increasing complexity and dynamism of the electrical system.
The expansion of electric vehicles (EVs) is a game-changer. EVs not only offer a cleaner alternative to traditional transportation but also have the potential to actively interact with the electricity grid.
EVs can function as distributed storage units through technologies such as Vehicle-to-Grid (V2G). Therefore, they supply energy back to the grid when needed and help balance supply and demand.
Additionally, smart EV charging optimises renewable energy use by charging during low-demand periods or when renewable generation is high, contributing to grid stability.
Overall, the integration of distributed generation, the adoption of electric vehicles, and enhanced system flexibility - under efficient DSO management - are essential for an electricity grid ready to meet future challenges.
