Interruptible Loads
The German transmission system operators (TSOs) with control area responsibility are required under § 13 (1) of the Energy Industry Act (EnWG) to ensure the security and reliability of the electricity supply system within their control areas. According to § 13 (6) EnWG, they are authorized to conclude contracts with providers of interruptible loads for this purpose.
The use of interruptible loads serves the immediate stabilization of the system frequency and is activated in the event of an underfrequency of 49.7 Hz. The use of interruptible loads as a substitute for automatically or manually activated balancing energy, or within the scope of redispatch, is not intended.
Activation of interruptible loads can be carried out either automatically via a frequency relay or manually through a decision by the transmission system operator. In the case of automatic activation, service provision must occur within one second of activation. Manual activation is carried out via an electronic dispatch signal or by telephone request. Automatic underfrequency disconnection serves as a supplementary measure to the European frequency targets with reserve deployment and precedes the underfrequency load shedding (UFLS) as part of the ten-step plan outlined in the system protection plan.
The remuneration for bids in the tender (award price) is based solely on a capacity price. Thus, the bid price includes compensation for both availability and the service provided. Participation in the tender requires prequalification as a provider of interruptible loads.