The power failure in Spain and Portugal has raised many questions – including the supply of electricity in Switzerland. What impact did the power failure have on Switzerland? How does the grid work? Swissgrid, the operator of the Swiss transmission system, answers the most important questions and provides clear explanations for anyone who wants to know more about the security of our electricity system and how it works.
The power failure in Spain had no impact on the Swiss transmission grid. Nevertheless, the event raised many questions. We summarise the most important concerns before defining the technical terms that are often used, but rarely explained.
What happened in Switzerland?
Although slight frequency fluctuations were measured in Switzerland, security of supply was guaranteed at all times. Swissgrid did not have to take any stabilisation measures of its own, but offered assistance to the grid operators in the countries affected. More specifically, Swissgrid was able to help balance out the fluctuations in the French grid caused by the outage.
How does the Swiss electricity system work?
Switzerland’s electricity system ensures a continuous supply of electricity across the country. To achieve this, the amount of electricity produced must always match current consumption. This balance between production and consumption is monitored around the clock by experts.
The Swiss electricity grid is divided into seven different levels, which transport electricity from power plants to households. First of all, the electricity is transported over long distances at extra-high voltage (Swissgrid’s transmission grid). On the way to people’s houses (distribution grid), the voltage is then reduced in several steps so that the electricity can be used safely.
As the national grid company and transmission system operator, Swissgrid constantly monitors the grid and ensures that it is operating stably at a frequency of 50 hertz. If there are minor deviations – for example because more electricity is suddenly needed than planned – Swissgrid compensates for them immediately. Major disturbances are very rare because the grid is constantly monitored and controlled and because it is closely networked across the continent. This ensures additional stability.
How secure is the Swiss electricity grid?
A nationwide power failure lasting several hours is a very unlikely scenario in Switzerland. Switzerland has one of the most stable transmission grids in the world thanks to a robust grid infrastructure, comprehensive monitoring and protection systems, and close networking with the European power grid. However, the experts are prepared for various scenarios and can act quickly in exceptional situations. The grid is always operated with n-1 security, meaning it remains reliable even if a single element, such as a line or transformer, fails.
The transmission grid must continue to be developed so that it meets future requirements.
What does a «stable» grid mean?
Electricity cannot be stored in the grid; thus, production and consumption must always be precisely balanced. Swissgrid monitors the balance in Switzerland around the clock. If there are fluctuations, the system frequency can fall or rise. If this happens, Swissgrid intervenes and, if necessary, obtains support from the transmission system operators in neighbouring countries.
Switzerland has one of the most stable transmission grids in the world thanks to a robust grid infrastructure, comprehensive monitoring and protection systems, and close networking with the European power grid.
How is Switzerland integrated into the European electricity system?
Switzerland is part of the European interconnected grid. This means that the electricity systems of European countries are interconnected, allowing electricity to be exchanged across borders, which increases security of supply.
Switzerland is located at the centre of the European interconnected grid and has played a key role in its development: in 1958, the «Star of Laufenburg» switchgear in Fricktal, Aargau, interconnected the transmission grids of Germany, France and Switzerland for the first time.
Why do we need a European electricity system?
Electricity does not recognise national borders and always seeks the path of least resistance. In physical terms, Switzerland is therefore constantly exchanging electricity with neighbouring countries. This makes cross-border cooperation essential.
Outages and other disturbances are easier to deal with in a large community. Our grid is part of the European interconnected grid (the European electricity system). If there is less electricity available somewhere in Europe in the short term, other countries can help out, making it possible to balance out fluctuations or outages more rapidly. This close cooperation makes the grid in Switzerland more stable and secure.
What will the situation be like in the future?
International cooperation is becoming increasingly important. Not all congestion can be resolved by measures in Switzerland alone – especially if it occurs at or near the border. In these cases, Swissgrid works with neighbouring transmission system operators.
An electricity agreement with the EU will integrate Switzerland into the European internal electricity market.
It will ensure the secure and stable operation of the Swiss transmission grid as part of the European interconnected grid in the long term.
What are the most important technical terms in relation to the grid?
| Grid | A network of lines and systems for the transmission and distribution of electrical energy. There are seven grid levels in Switzerland. |
| Transmission grid | The transmission grid (grid level 1) transports large volumes of electricity over long distances at very high voltage. The extra-high-voltage grid forms the backbone of a secure electricity supply. It is like a motorway for electricity. Swissgrid is the owner of the Swiss transmission grid. This grid, which is over 6,700 kilometres long, transports electrical energy at a voltage of 380 and 220 kilovolts. |
| Distribution grid | The distribution grids (grid levels 2 to 7) transport electricity from the substations to Swiss households. To do so, the voltage must be reduced by a factor of 1,000 (from 220,000 volts to 230 volts, for example). This takes place across multiple stages and different grid levels. |
| Interconnected grid | The interconnection of several grids across national borders in order to provide mutual support. The interconnected grid in Europe transports electricity for over 500 million people in more than 30 countries. Switzerland is at the geographical heart of this huge machine and is closely connected to it by 41 cross-border lines. For this interconnected system to function, Switzerland must work closely with its European partners. |
| Voltage | Voltage is the «drive» for the electric current. It ensures that electrons can move in the circuit and that current can flow. It indicates how much energy is required to move the electrons. In Switzerland and Europe, the voltage for power outlets is usually 230 volts. If you imagine electricity flowing through a pipe like water, the voltage would correspond to the pressure in the water pipe. |
| Intensity of current | The amount of electrical charge that flows through a conductor per second. It is measured in amperes. If you imagine electricity flowing through a pipe like water, the intensity of current would correspond to the amount of water flowing through the pipe per second. |
| Grid stability | Electricity cannot be stored in the transmission grid, so the amount of electricity fed in must always be the same as the amount of electricity fed out. This means that the production and consumption of energy must always be balanced. |
| Control energy | The System Operations Specialists in the grid control rooms use control energy to manage unforeseen fluctuations in the grid. Control energy is a reserve that certain power plants keep available for short-term use and can be called upon when needed. Keeping the balance between production and consumption in the European interconnected grid consists of three stages:
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| System frequency | The Swiss transmission grid is operated at a frequency of 50 hertz, as is the European interconnected grid. This means that the current in the AC grid (Alternating Current grid) changes direction 50 times per second. To ensure that the frequency always remains stable, the production and consumption of the electrical output must always be properly balanced. Swissgrid works with the other transmission system operators to ensure that the frequency in the interconnected grid can be maintained at all times. |
| Power system failure | A large-scale power failure can be triggered by a combination of several factors. These include extreme weather events, technical faults or instabilities in the European interconnected grid. However, individual events are usually reliably intercepted by the system’s protective mechanisms. |
| Automatic start-up | Emergency procedure for restarting a power plant after a power failure. |
| Grid restoration | After a power failure, black start-capable power plants such as pumped storage stations start up. They set up small island grids without external voltage, stabilise the frequency and voltage, and supply energy to the first consumers. Additional power plants and grids are gradually connected. Swissgrid controls and monitors this complex process carefully in order to restore the electricity supply quickly, safely and in a coordinated manner. |
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