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.