The service providers that operate the infrastructure of supra-regional power networks and are in charge of their maintenance are referred to as transmission network operators. For example, they also make sure that network fluctuations are kept low. In Germany, there are four transmission network operators:
- Tennet TSO
- 50 Herz Transmission
- Amprion and
As the transmission network operators hold a natural monopoly, there are statutory regulations to ensure non-discriminating network access.