Abstract

The increasing market penetration of renewable energies is generally directly related to an increasing number of power electronic systems in the grid. Accordingly, a continuous change of the harmonic situation is to be expected depending on the operating state of the plants. Simulations are often not sufficient to represent the real situation of current and voltage harmonics. In the transmission grid, suitable measuring systems are available for voltage measurement, such as RC dividers or capacitive bushing dividers. For current measurement, however, there are currently no suitable measurement systems available, especially for retrofitting installed transformers. In addition, existing problems such as inaccuracies in the billing measurement by conventional inductive current transformers have not yet been solved across the board. Parasitic DC components and frequency components below 50 Hz can also occur at all voltage levels and adversely affect the magnetic operating point of inductive equipment such as current transformers. In low-voltage applications, these problems are already being addressed. In higher voltage levels, this development has not yet arrived. Fluxgate current transducers have been used for decades in test facilities for high-accuracy power measurements and in HVDC projects and offer significant advantages over conventional current transformers for a variety of measurement tasks in the AC transmission network. The sensors can be used in new transformers as well as for retrofitting existing transformers. Due to the highly accurate current measurement from DC up to the three-digit kHz range, a reliable measurement of current harmonics can be performed. Transient phenomena in the network can also be measured, which in turn can be used to determine network impedances.

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