On-site SFRA at MV LPVTs and VTs for Metering Application - Investigation of Test Voltage Dependency

The increasing integration of renewable decentralised energy generation is changing modern power grids. New generation technologies introduce non-linear loads and bi-directional power flows, resulting in signal distortions, transients, and added harmonic and sub-harmonic components. These phenomena pose challenges to maintain grid stability, and elevated power losses and partial over-voltages can ultimately shorten the service life of installed assets. As a result, assessing the current grid condition through accurate power quality measurements has become increasingly important. Reliable power quality assessment requires evaluating the entire measurement chain [1]. This measurement chain comprises the instrument transformer, which converts the primary electrical quantity into a measurable secondary signal; the secondary transmission cable; and the power quality meter, which detects and analyses grid characteristics in accordance with relevant standards, such as IEC 61000-2-4. In the past, the frequency transfer behaviour of instrument transformers was not subject to standardisation and accuracy requirements were specified only for the rated grid frequency. Many instrument transformers, e.g.