Spectral grid impedance identification on different voltage levels — Challenges and realization

The frequency dependent source impedance at the terminals of a main supply network is an essential parameter for power quality and grid feedback analysis. The identification requires a spectral excitation at the corresponding terminals, which generates measureable changes in the network voltage spectra. This contribution investigates the spectral grid impedance identification on different voltage levels through fast switching of an ohmic load with power electronic switches. 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 developed. The requirements and setup of these systems are outlined. Further on 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.