Controlled island operation of part of the 50-kV grid in Southern Sweden

This paper is based on measurements obtained during a test of controlled islanding of part of the 50-kV grid in Southern Sweden. The purpose of the test was to verify operation of generator controls during islanding. The variations in voltage magnitude and frequency are shown as well as flicker severity and very-short variations. A number of performance indices have been calculated and compared with limits. Voltage magnitude and frequency have been studied in some detail around the disconnection and reconnection instants. The frequency varies much more during the island operation than during grid-connected operation. Voltage magnitude variations and flicker remain within their normal range. However the variations in the time range between 3 seconds and 10 minute appear to be higher than normal.