Calibration Method for an On-Line PLC Blocking Filter Characterization System

The characterization of EMI filters is mostly performed off-line, without a load and with 50 Omega terminations or standard LISN. This leads to a different filters behavior as when connected to the mains. Due to growing PLC demand as part of the digitalization of the power grid, the impedance and attenuation behavior of the filter under realistic conditions becomes increasingly important. An on-line PLC filter characterization system requires a calibration to gain accuracy and minimize disturbance. In this paper, a calibration method of such a system to characterize EMI filters under realistic conditions in the narrowband-PLC range up to 1MHz is presented. Problems with former calibration approaches are discussed and the improvements are shown.