On 18 September 2010, Turkey was connected to the European electricity grid via three new feeder lines to Bulgaria and Greece. This step was the outcome of extensive examinations and adjustment work carried out by the Steinbeis Transfer Center for Applied Research in Electrical Power Engineering at the University of Rostock. The team of Steinbeis experts addressed issues such as primary regulation and frequency stability, secondary regulation, inadvertent interchange, and dynamic behavior for operation – when connected and in isolation.
Turkey has been looking to connect its energy supply system to the European grid since the 1970s. Joining the European grid brings major benefits: a more secure energy supply, a more stable utility frequency, easier regulation, and the ability to trade power with European neighbors. But the requirements for connecting to the European grid, as specified in the ENTSO-E Transmission Code, are high. Candidates must prove that the primary regulation of their power plants is stable and functional – and can compensate for lost power within 30 seconds if a power plant goes offline. This is done by using energy from all other power plants at a somewhat reduced utility frequency.
The primary regulation must also guarantee a steady, non-oscillating frequency response during normal operation. Potential candidates must also have a functioning secondary regulation which can make up for lost power within 15 minutes, using dedicated secondary power plants. This also involves returning the reduced utility frequency to the usual 50 Hertz. If not present, these functions may need to be implemented before being tested to see if they are effective.
Another prerequisite for joining the grid is avoiding and actively damping oscillations. This phenomenon, roughly comparable with the oscillations created by two weights connected by a spring as they swing, occurs across the European grid as a whole, between the generator rotors of Spain and Turkey. The rotors spin in opposition to each other: if the rotors in Spain speed up, the ones in Turkey slow down, and vice versa. The more the European grid is enlarged, the less stable these pendular oscillations become – and the more danger they pose to safe operation.
To meet these requirements, ENTSO-E (formerly UCTE) commissioned Amprion GmbH in Essen (formerly part of German energy company RWE) to set up a project group comprising specialists from all countries involved in the project. The Steinbeis Transfer Center for Applied Research in Electrical Power Engineering is acting as a consultant for Amprion in the project. To study the behavior of the Turkish grid in advance, the Steinbeis experts created detailed simulation models of both the Turkish grid in isolation and the resultant combined grid. The large hydroelectric power plants in the east of Turkey have a major effect on the dynamic behavior of the Turkish grid – so these plants, their hydraulic systems and regulation systems were modeled very precisely. These models made it possible to investigate the system and see the extent to which it met UCTE requirements, and make recommendations for safe, stable operation. These recommendations included regulation optimizations and recalibrations in the power plants, as well as the addition of supplementary damping devices both in power plants and the grid itself.
Currently, deviations in the system are still being reduced by introducing more optimizations. As a result, thanks in part to the assistance of the Steinbeis Transfer Center, nothing stands in the way of continued joint operation between the Turkish and European power grids.