Spectral grid impedance identification on the low-, medium- and high-voltage level - System design, realization and measurement results of grid impedance measurement devices

Abstract

The frequency dependent grid impedance at the terminals of an electrical supply grid is an essential parameter for power quality and grid feedback analysis. In this contribution the identification of the grid impedance is achieved using spectral excitation currents at the corresponding grid connection point, which generate measureable changes in the grid voltage spectra. Different measurement systems based on this method have been successfully realized for the low- and medium-voltage level. A measurement system for the high-voltage level is currently being realized. The application of the measurement systems are facing quite different external framework conditions leading to specific system designs for each measurement device. The spectral grid impedance identification on these voltage levels is done through fast switching of an ohmic load with power electronic. The requirements and setup of the grid impedance measurement systems are outlined and measurement results on the low- and medium-voltage level are presented and discussed. The systems can be used to evaluate grid connection points and to verify other active or passive grid impedance identification methods on different voltage levels.