Online Network Impedance Spectrometer for the Medium-Voltage Level

The network impedance is an essential parameter for power-quality, stability and control design considerations of power systems. The frequency characteristic of the impedance often includes distinct resonances which may also vary over time due to changing load or generation conditions in a network. The time variation as well as the lag of detailed frequency models of different power systems components make an exact analytical or simulative identification of the spectral network impedance challenging. This contribution introduces a novel measurement system. The system can precisely identify the spectral network impedance of power systems at the medium-voltage level (up to 20 kV) from DC to 20 kHz. The basic technical design and the general identification method of the system is illustrated. Furthermore, measurements carried-out with the system at a medium-voltage connection point are presented and discussed.