Harmonic Network Impedance Measurement and Modelling on the Medium Voltage level

The harmonic emission of loads and generators with power electronic grid coupling strongly depends on the network impedance at the corresponding connection point. This contributions presents frequency-dependent network impedance measurements on the medium-voltage level at a wind farm connection point (20 kV). Different switching operation have been done in the wind farm to analyse their impact on the harmonic network impedance. Further on, long time measurements have been carried out. The results show time varying resonances in the frequency characteristic of the network impedance. From the measurements accurate frequency-dependent line models can be derived.