Static And Dynamic Voltage Control

The transmission of electrical energy requires grid voltages to remain within the permissible operating limits. Due to the impedance of network equipment and changing load and generation conditions, voltage variations occur throughout the grid, requiring the provision and control of reactive power. Voltage control comprises both steady-state and dynamic control measures to maintain voltages within the permissible operating range. While steady-state voltage control ensures continuous operation within the defined operating limits, dynamic voltage control serves to stabilise the power system following disturbances. Static and Dynamic Voltage Control therefore constitutes a key operational function in transmission and distribution grids.

The required reactive power is generally provided by the network operators’ equipment and by technically suitable facilities of connected network users in accordance with the Technical and Organisational Rules (TOR).

Procurement Concept

The procurement of the non-frequency ancillary service Static and Dynamic Voltage Control is carried out locally, as reactive power can only be transmitted over limited distances due to its physical characteristics and demand therefore depends on location. Owing to limited market liquidity in local network areas and the risk of inefficient procurement outcomes, procurement is based on a remuneration model under standardised and transparent bilateral contracts. Participation in the procurement process is voluntary.

The provision and activation of the service take place at the contractually agreed point of connection. All obligations to comply with the requirements of the TOR, such as the required reactive power capability, remain unaffected by the procurement of the NFAS.

Becoming a provider

Step 1:

APG offers all grid users connected to the APG transmission grid the opportunity to conclude a Reactive Power Contract, based on the TOR, governing the remuneration for the provision of the NFAS.

Participation is subject to compliance with the technical, organizational and contractual minimum requirements specified in the Information Sheet for Providers. In particular, the Information Sheet sets out the requirements relating to grid connection, technical capability, and the required measurement, communication and control functionalities.

Step 2:

To demonstrate compliance with the participation requirements and to enable the technical assessment of the facility, the information and supporting documents specified in the Information Sheet for Providers (Section 2, Required Documentation) must be submitted to APG no later than the start of the service provision period. These include evidence of compliance with the minimum requirements, technical information on the facility and, where applicable, information on any required retrofit or upgrade measures.

The reactive power products defined by APG are described in Section 2 of the Reactive Power Contract. The product applicable to the respective provider is specified in the Reactive Power Contract.

The service provision period commences on the date specified in the Reactive Power Contract and, unless otherwise agreed, is concluded for an indefinite period.

Step 3:

The award of a contract is subject to the timely fulfilment of the participation requirements and the successful completion of required data interface and conformity tests. Upon awarding the contract, a Reactive Power Contract based on the published standard contract is concluded between APG and the provider.

Step 4:

Once a provider has been awarded a contract under the procurement process, it is required to ensure the contractually agreed provision of reactive power throughout the service provision period and to deliver the requested reactive energy. During the service provision period, APG is entitled to monitor and verify the contractual provision of the non-frequency ancillary service by appropriate means.

Entitlement to remuneration

Providers awarded a contract are entitled to remuneration for the provision of reactive power in accordance with the remuneration model set out in the Reactive Power Contract. One-time costs incurred for retrofit and upgrade measures may be reimbursed in accordance with the provisions of the Reactive Power Contract. Settlement is carried out annually.

Remuneration model

The non-remunerated base range comprises the underexcited operating range of the generating unit up to the technical capability limit at the point of connection. Outside this range, the agreed product is remunerated. Therefore, reactive energy quantities are converted into active energy equivalents using loss coefficients.

For activations of special measures (e.g. phase-shifter operation and generator synchronisation), the associated active power losses are remunerated in addition to the renumeration for reactive power provision, using a loss factor of 7.5 kW per MVA of generator apparent power. For the assessment of the prevailing spot price, the quarter-hourly Day-Ahead prices of the Single Day-Ahead Coupling (SDAC) for Austria shall be used.
Compensation for additional effort (e.g. manual activations) is agreed contractually.

The applicable loss coefficients are differentiated by generation technology:

• Run-of-river hydropower plants: 10.56 kWh/Mvarh

• Pumped-storage power plants: 7.50 kWh/Mvarh

• Converter-based generation facilities: 10.00 kWh/Mvarh

• Thermal power plants: 8.50 kWh/Mvarh

• Other power plant types[1]: 8.85 kWh/Mvarh

[1] For generating units that are not contractually assigned to any of the specified technologies.