The operators in the grid control room at Swissgrid are not just responsible for protecting the transmission grid from fluctuations but also for protecting it against high loads. Lines and transformers can transmit only a limited amount of energy.
To prevent a grid element from overloading, Swissgrid uses the n-1 rule, which means that if a grid element fails, all the other grid elements in the transmission grid must still have enough capacity to transmit the additional energy. Every 5 minutes, the automatic grid calculation simulates whether this rule is being upheld. If the n-1 rule is violated, lines or transformers are at risk of overloading, and the operators jump into action.
They can use switching operations to influence the load flows in the transmission grid, meaning they disconnect or connect lines in substations or adjust the flow of electricity through the transformers. This makes it possible to reduce the load on a certain line.
The operators in the Swissgrid grid control rooms also have the option of carrying out a redispatch. A redispatch instructs certain power plants to reduce their production and others to increase their feed-in. All in all, the same amount of energy is still fed into the grid; it is simply geographically redistributed to reduce the load on the line that is at risk.