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Ancillary services

Ancillary services in the electricity supply sector are defined as services provided by grid operators to customers in addition to the transmission and distribution of electrical energy. To ensure the secure operation of the system. Swissgrid organises the following ancillary services as part of its legal obligations:   

  • Control power (primary control, secondary control, tertiary control)
  • Voltage support
  • Compensation of active power losses
  • Black start and island operation capability
  • System coordination
  • Operational measurement

To meet its ancillary services obligations, Swissgrid concludes a framework agreement with service providers following a technical and operational appraisal of providers and their power plants (prequalification). This is the basis for the participation of providers in ancillary service tenders.

How the AS (ancillary services) market works

Electricity or electrical energy cannot be stored in large quantities by conventional means, For this reason, at any given point in time, the amount of electricity produced must correspond precisely to the amount being consumed. This balance guarantees the secure operation of the electricity grid at a constant frequency of 50 Hertz (Hz). Unforeseen fluctuations between the feeding-in and withdrawal of electrical energy in the grid must be balanced out at short notice, which is done by the suppliers of control energy increasing or reducing power plant output.

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The animation shows two situations which lead to instability of the grid and therefore the grid frequency. The grid is stable when production and consumption are in balance. The situations show the measures swissgrid undertakes when production and consumption are not in balance: by increasing consumption or production.

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Overview of ancillary services market

Swissgrid does not own any power plants and must therefore buy all its ancillary services on the electricity market. The majority of ancillary service costs incurred are covered by all power plants with an output of more than 50 MWh. A far smaller part of the costs for  ancillary services are passed on to all electricity consumers by means of fixed billing prices.

The diagram shows that swissgrid buys reserve energy and reserve power from the procurement market. swissgrid uses the procurement tool to request the most favourable bid prices. The reserve energy and reserve power are imported or exported by swissgrid as required to ensure stability on the high-voltage grid, i.e. the balance between electricity consumed and electricity generated. The costs incurred in this process are passed on to all end consumers and to all power plants with an electrical output of at least 50 MW. swissgrid is monitored by the Electricity Commission throughout the process. Graphic: Overview of ancillary services market (PDF / 111kB)

 

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