On Monday, 20 May 2019, a critical situation occurred in the Swiss transmission grid. Individual grid elements were significantly overloaded or threatened to be overloaded (n and n-1 violations).
The on-going analysis of the incident shows that during a period of high domestic production (around 12 GW), a total of around 4.5 GW was exported, a large part of it to Germany. Load flows typically go in the other direction, from Germany to Switzerland. This atypical export and production situation lead to violations of grid security (n and n-1).
Initial analyses have determined that, due to the energy trade, the exported amounts increased for a short time between Sunday and Monday. For reasons that are still unknown, European grid prognoses did not recognise these violations in advance. They had to be dealt with in real-time operation in close collaboration with other European transmission system operators.
This incident shows that the prognoses can differ significantly from the effective load flows. It is therefore enormously important that all transmission grids in Europe, including in Switzerland, are included in the grid models, so that potential violations in grid security are recognised in the prognoses and coordinated measures can be taken to avoid the occurrence of such violations in real-time operation.
As Switzerland is excluded from market coupling due to the lack of an electricity agreement with the EU, it must be assumed that disparities between prognoses and effective load flows will continue to increase. An electricity agreement would allow Swissgrid to be included in the models for load flow calculation and allocation of capacity of the European partners and provide Swissgrid with better knowledge of the load flows through Switzerland.
Swissgrid is investigating the incident. These in-depth analyses will probably take several weeks.