Phasor measurement of wind power plant operation in Eastern Denmark

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INTRODUCTION
Energinet.dk is the independent system operator (ISO) in Denmark. Until 2005 Elkraft System was the
ISO in Eastern Denmark, and this project was run as an Elkraft System project in corporation with
Centre for Electric Technology at Technical University of Denmark.
The transmission grid in Eastern Denmark encompasses overhead lines and cables at the two highest
voltage levels, i.e. 132 kV and 400 kV, and the interconnections with South Sweden and Germany.
The page link to Germany is a 400-kV DC interconnection with a transmission capacity of 600 MW. The
interconnection with Sweden consists of AC interconnections with a total capacity of some 1900 MW.
The page link with Sweden also serves as an interconnection with the Nordic grid. The maximum load in
Eastern Denmark is about 2870 MW and the total installed capacity is 4360 MW. The eastern Danish
transmission system is shown in figure 1.



MEASUREMENT SYSTEM
On that background, a total of four PMU units have been installed in the 400 kV and the 132 kV
system in Eastern Denmark. The PMU units are developed and built in collaboration between Elkraft
System and Centre for Electric Technology (CET) on Technical University of Denmark. Since the
PMU’s are built at CET all information about the measurement method are known in every detail. The
locations of the four PMU’s are shown in figure 1.


AIMS OF THE PROJECT
The main purpose with the PMU project is to do research work. In the future PMU data is expected to
become a helpful tool in daily control room routines and system protection.
In the first hand, the research work covers the following subjects:


CASE: STORM IN DENMARK 8 JANUARY 2005
On 8 January a severe storm with wind speeds up to 28 m/s passed Denmark. Because of high
mechanical and electrical loads at such high wind speeds, the wind turbines must be disconnected
from the grid and shut down. This also happened for the Nysted offshore wind farm located south of
Lolland (figure 1), which disconnected from the grid app. at 13:30 .