Characterization of Digitizers for Combined and Composite Waveform

Driven by the increasing demands on traceable measurement systems and given the importance of having reliable electricity grids able to support renewable energy sources and the growing energy demand for electric mobility, there is an imperative need for an adequate grid components testing. The typical tests on high voltage electricity grid systems include the combined and composite voltage tests, during which lightning or switching impulses are superimposed on the High Voltage Alternating Current or High Voltage Direct Current. However, at present, there are inadequate traceable measurement systems that can be directly connected to the equipment under combined and composite high voltage tests, which may result in unreliable test results. Combined and composite waveform measurements are complex due to their characteristics. The aspect addressed in this paper is to verify the capabilities of the recording instruments used for measurements. Nowadays, there are a lot of off-the-shelf digitizers with adequate accuracy and uncertainties for the measurement of impulse voltage and current. In high voltage testing and calibration, these digitizers are used not only in the measurement of impulse voltage but also composite and combined voltages. The current IEC 60060 standard series do not provide evidence for the ability of such measurement systems to accurately measure combined and composite voltages. Furthermore, there is a lack of standardization in the IEC 61083 series for measuring instruments and software used for combined and composite wave shapes measurements. This paper includes the characterization results of commercial digitizers which are the brands of Dr. Strauss TR-AS 200/12 and National Instruments oscilloscope PXI-5124 on DC and lightning impulse (LI) performed by INRiM and TUBITAK. This paper arises in the context of the European project 19NRM07 Hv-com 2 which support the standardization in high voltage testing.