Firm and flexible

Firm capacity is capacity available at all times of the year. Swissgrid retains the right to curtail demand and/or production in order to maintain system stability and security.

The analyses are based on a model that reflects the grid configuration envisaged for the specific time horizon, assuming that all the grid elements that make up the Swiss system are in operation. This provides a dynamic view of the system, taking into account new developments, enhancements and modernisations. In the event of outages of grid elements, the absorption capacity is generally lower than that shown on the maps. A market simulation is carried out for the entire year covered by the relevant time horizon. This determines the expected consumption, generation and cross-border electricity exchange for each European market area on an hourly basis. 

Once the results have been integrated into the grid model, the outgoing load flows in the electricity grid can be calculated prior to the connection of the new plant. Load flows are analysed for every hour of the year in question. This approach makes it possible to identify critical periods, potential congestion and the available power reserves for additional loads and/or generation. A specific observation zone is defined for each feed-in or feed-out allocated to a grid node. The limitation of this zone is based on sensitivity analyses and load flow simulations. An observation zone comprises those grid elements whose load flow could be significantly affected by a variation in power output at the relevant node. 

Connection capacities are calculated on an hourly basis for the entire year by linearising the load flows on the basis of sensitivity factors (Power Transfer Distribution Factor, PTDF). The analyses take into account the seasonal thermal limits of all grid elements within the observation zone, as well as the (n-1) security criterion. The maximum power that can be fed into or out of a node is reached when the load flow on one of the monitored elements reaches its seasonal capacity limit. The already allocated capacity, existing capacity and reserved capacity at each grid node in the Swiss grid are deducted from the figures calculated. This allows the feed-in and feed-out volumes that are actually still available to be calculated for each node. An indicative assessment of the connection feasibility at the substations is provided on the basis of the existing plants and the available space.

Flexible capacity garantees an availability of the capacity for 90% or 80% of the time with a complete grid respecting the N-1 criterion. Swissgrid retains the right to curtail demand and/or production in order to maintain system stability and security.

Statistics on the connection capacities of the Swiss grid make it possible to quantify the system’s flexibility and robustness with a view to integrating new feed-ins or feed-outs. They indicate a minimum value that guarantees connection capacity throughout the year without any constraints, as well as flexibility values representing the available capacity 90% or 80% of the time – depending on the grid connected party’s operating conditions (ability to modulate the new feed-in or feed-out power during grid overloads)

The connection capacities shown on the capacity maps are intended for guidance only. The figures are indicative and are subject to verification on a case-by-case basis, according to the latest assumptions and information available. No entitlement to a grid connection or grid access can be inferred from the information given on the capacity maps.