Tham khảo tài liệu 'electricity infrastructures in the global marketplace part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Europe Status of Integrating Renewable Electricity Production into the Grid 269 The solution to the second problem grid enhancement is restricted by legal difficulties and the long-term permission process for installation of new transmission lines. Moreover existing conventional power stations will offer their generating capacity on the free market selling it throughout Germany or Europe. Consequently free energy trading is suffering increasing constriction owing to a lack of transmission capacity and the installation of new transmission capacity will become mandatory. But from an economic viewpoint it is just the time to rethink the situation and to consider whether the network ought to be expanded for about 60 strong wind days per year or whether generation management for wind power installations ought to be approved for this relatively short time. Thirdly apart from local impacts wind power also has a number of system-wide impacts because it affects power system dynamic and stability reactive power control and voltage control frequency control and load following dispatch of conventional units. The wind generators should fulfill three main aspects no excitation of power oscillations after grid disturbances in-feed of reactive power during and after system faults maintaining system stability minimize grid disruption. Wind turbines installed in the German power system before 2003 had a single response to fault situations on the grid that resulted in instantaneous voltage drops they were tripped off to protect their function until the grid recovered. The immediate loss of generation can impact on system stability and lead to cascaded tripping of some thousand MW of wind power. Reference 3 shows that faults in some grid locations can cause power tripping that is much higher than the whole spinning primary reserve of the European Network of Transmission System Operators for Electricity ENTSO-E grid of 3000 MW. For this reason new rules for grid connection of wind .
