Planning for winter

Ensuring secure grid operations in Switzerland is always more challenging during the winter. In Switzerland, more energy is consumed in the winter than in the summer. Switzerland is therefore dependent on imports in winter to cover the increased domestic electricity demand.

The grid situation was stable and non-critical over the entire winter 2016/2017. Switzerland’s available net import capacity has once again been increased, and is much higher than last year. As far as possible, shutdowns have been postponed until after the winter.

By the end of January 2017, the resulting import capacity was only partially used and was below 50% on average. During the cold wave, due to the very high level of power generation from hydro storage plants, the water levels in the reservoirs since the end of January 2017 reached a new seasonal low. However, much higher imports have been recorded in February. This causes a greater strain on the grid, particularly for transfomers; however, this was not at a critical level. The discrepancy with the established median on the high-water level curve has continuously diminished as a result and as of the end of March was again at a customary level for the season.

As part of its responsibilities, Swissgrid has taken all necessary measures to ensure that the transmission grid is available at all times. Market players have access to a tool that they can use to estimate the net import capacity in various load flow situations. Furthermore, Swissgrid had reserved power plant output in February 2017 («winter hedging products») that could be accessed in extreme grid situations in order to manage congestion. Such a situation could occur, for instance, if a transformer malfunctions while imports are very high.

In the environment of very mild temperatures in March 2017 the energy situation in Switzerland sustainably relaxed in view of the lower electricity load and the nuclear power plant Leibstadt resuming operation. in the middle of March, Swissgrid also put the new 380/220-kV transformer in the Beznau substation into operation, as planned in the 2025 strategic grid. It supports the import capacity at the Swiss northern borders and improves the reliability of supply.

In view of the favourable supply situation the start of April in the neighbouring countries, extraordinary situations (power plant outages, delayed snow melts, etc.) can for the most part be covered via additional net imports.

Precise observation of the general situation will therefore remain necessary in the coming weeks.

Swissgrid is responsible for operating, maintaining, modernising and expanding the transmission grid with voltages of 380 kV and 220 kV on grid level 1 to meet demand. Swissgrid thus plays an important role in maintaining security of supply in Switzerland.

Because of its greater transfer capacity, the 380 kV grid is used to transport and exchange electricity with other countries. A large part of domestic production occurs at the 220 kV level. Switzerland’s energy is also supplied primarily via the 220 kV grid and other transformation systems at lower grid levels.

During the winter half-year, 75-85% of imports and 80-90% of exports are transported at the 380 kV voltage level. In the case of imports, this usually happens via the cross-border lines with the northern neighbours France, Germany and Austria.

The capacity of the transformers that convert the energy from 380 kV to 220 kV largely determines how much imported energy can be used to supply Swiss consumers. As the capacity for transforming from 380 kV to 220 kV is limited, imports can only be utilised to a limited extent to cover Switzerland’s electricity demand.

Structure of the Swiss transmission and distribution grid

During the winter, Switzerland’s energy supply is met by domestic production and net imports from neighbouring countries. In addition to the available base-load energy, the utilities also use water reserves from the reservoirs to cover part of the consumption with peak energy. The amount of peak energy supplied by storage power plants depends on the electricity demand.

  1. Switzerland's electricity consumption and how this demand can be met can be explained using the example of a bathtub. The bath represents consumption. The greater the consumption, the larger the bath.
  2. The electricity supply can be represented by the quantity of water in the bath. It is made up of various components:
    1. Net imports: these imports are largely delivered via transformers from 380 kV to 220 kV and lower voltage levels to the consumers.
    2. Energy from nuclear and run-of-river power plants: Both types of power plants supply so-called 'base-load energy' and account for a significant proportion of the water in the bath.
    3. Energy from storage power plants: the water in the reservoirs forms an energy reserve, which empties between around October and early May each year and is replenished in the summer months. Storage power plants supply so-called 'peak-load energy'.
  3. The bath also has a tap and a plug hole. The inflow from the tap represents imports and the outflow through the plug hole represents exports of energy abroad. The difference between inflow and outflow represents the net imports. Any energy which is exported is not available to supply to consumers in Switzerland.

Energy supply and consumption in Switzerland

The reservoir levels are published weekly by the Swiss Federal Office of Energy (SFOE) and provide information on the water reserves available for electricity generation in Switzerland. The Swiss storage power plants are the only flexible domestic power resource and therefore play a central role in guaranteeing secure grid operation. They provide control energy in order to ensure a constant balance between electricity consumption and production, and they can be deployed in critical grid situations for redispatch measures. The responsibility for reservoir management lies with the power plant operators.

Date Description Format
18.09.2017 Current reservoir levels PDF

During the winter of 2015/2016, energy companies, grid operators and authorities successfully cooperated to manage the strained energy and grid situation. The situation was analysed in the «Working group Winter», and measures and solutions were developed. Swissgrid and ElCom recommend agreeing on a plan early so all the players are able to act quickly and decidedly in case the situation intensifies.

Swissgrid and ElCom have convened the «Working group Winter» again this winter. The first meeting took place on 3 November 2016.

German presentations of the Working group Winter

Date Description Format
16.02.2017 Präsentation Arbeitsgruppe Winter PDF
03.02.2017 Bericht vorgezogene SDL-Beschaffung Winter 2016/17 PDF
02.02.2017 Präsentation Arbeitsgruppe Winter PDF
17.01.2017 Präsentation Arbeitsgruppe Winter PDF
13.12.2016 Szenarien für die Netto-Importkapazität der Schweiz
im Winter 2016/2017
01.12.2016 Präsentation Arbeitsgruppe Winter PDF
03.11.2016 Präsentation Arbeitsgruppe Winter PDF
03.11.2016 Präsentation ElCom PDF

Netto Import Tool

As proposed by the working group on «Responsibility for the security of electricity supply», the «Netto Import Tool» should provide market participants with information about the maximum net import capacity of Switzerland. The net import capacity is the amount of imported energy that can be transformed unto the lower voltage levels in order to serve customers in Switzerland.

The tool allows market participants to estimate the Swiss net import capacity for different load-flow scenarios. This should help them to plan their portfolios in a such a way that they can fulfill their contractual and in some cases legal obligation to deliver energy and be balanced. Please note that the results are indicative only. The assumptions and limitations for the calculations are specified in the worksheet.

Date Description Format
30.01.2017 Netto Import Tool XLSB