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:

  • Frequency control (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.



Overview of ancillary services market

Swissgrid does not own any power plants and must therefore buy all its ancillary services on the electricity market. Until now the majority of ancillary service costs incurred were covered by all power plants with an output of more than 50 MW. A far smaller part of the costs for ancillary services were passed on to all electricity consumers by means of fixed billing prices. According to the decision of the Swiss Federal Administrative Court on July 8, 2010, ancillary service costs should not be covered anymore by power plants with an output of more than 50 MW. This charge, specified in the Electricity Supply Act, is illegal. Newly, Swissgrid has to pass all costs on to the electricity consumers.

Graphic: Overview of ancillary services market (PDF / 110kB)