Phasor Measurement Units in the Eastern Danish power system

In the Eastern Danish transmission system four Phasor Measurement Units (PMU’s) are installed at 400 kV and 132 kV voltage level. The PMU’s continuously record voltage and current phasors each 20 ms. Data are stored locally on the PMU’s and are also transferred to a database at Centre for Electric Technology. After power system events data can be extracted and analyzed offline. The purpose of the project is to do research within various utilizations of PMU data. On 8 January 2005 a severe storm passed Denmark, and wind speeds were so high, that wind turbines disconnected from the transmission grid because of their self protection. Nysted offshore wind farm was among the wind power units that disconnected from the grid, and PMU data from that event are analyzed. The case illustrates the close relation between voltages, power flows and voltage phase angles over a wide area. The voltage phase angle measurements complements the traditional voltage and power flow measurements.