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Twenties, R&D project in Spain

Overload control of a 220 kV transmission line by means of an OLC

TWENTIES is an R&D project funded by the 7th Framework Programme of the European Commission with the objective of increasing the wind power penetration in the European grid. A specific task force deals with the flexibility enhancement of the European transmission grid by installing new equipment that enables more efficient power flow control to optimize network capacity and allow increasing wind integration. Increasing wind power penetration in current networks will contribute to the objectives of the European Union known as “20/20/20”, i.e. 20% reduction of CO2 emissions, 20% improvement of energy efficiency and 20% energy consumption from renewable sources.   

Hitachi Energy has installed and commissioned an OLC, Overload Line Controller, based on a system of discrete series reactors that enable efficient control of the power transmission conditions, limiting system overload and controlling the compensated line loading conditions with a response time of fractions of a second.

The OLC is a simple and effective FACTS (Flexible AC Transmission Systems) solution to provide power flow control, power flow limitation and overload mitigation, particularly in such cases where the transmission lines are part of power networks with high penetration of wind energy sources.

The OLC is integrated in series in one of the main 220 kV corridors in Spain in the Aragón-Navarra region, forming part of the national Spanish power grid owned and operated by REE (Red Eléctrica de España). Under certain conditions, the selected region has limitations in its transmission capacity due to overload of the corridor. By integrating the OLC, this problem can be diminished, or even eliminated, consequently increasing the renewable generation that can be transmitted.  The OLC is located at the Magallón substation of the 24 km Magallón-Entrerrios 220 kV line.

The general purpose of the OLC is to provide the line with power flow control and operation closer to its natural limits, thereby increasing the transmission capability of renewable energy.

Main data
Commissioning year: 2013
System voltage: 220 kV
Nominal line current: 1250 A
Total rated impedance: 18.1 Ω
Series reactors:
  Reactor power (Mvar)
  Reactor impedance (Ω)
L1         L2          L3
12        24.5       48
2.6       5.2        10.3           

Twenties R&D project - Overload control