Including differential current monitor and certified consumption values
Initial situation
The topic of power quality (also known as PQ) now has many facets. In this way, not only the actual phenomena of power quality according to the standardisation of electromagnetic compatibility (EMC) according to IEC 61000-x-x are considered. Rather, other important parameters are being added all the time to support security of supply, and in some cases even legal certainty on the consumer side. Increasingly, this also includes consumption values, which are relevant for reducing CO2 emissions to a more climate-friendly level. In combination and as a minimum, however, all of the above criteria require a solid measurement as a basis.
Problems
Accuracy of the measurement questioned
Measuring instruments are usually classified according to standards and accuracy. Accuracy is an important indicator for being able to usefully build on a solid measurement result in the analysis and its resulting measures. However, it can be observed that although the measuring devices used correspond to a required accuracy class, the necessary sensors are often less in focus.
It can be seen that although class A measuring devices used in power quality applications correspond to a data sheet accuracy of 0.1 % for U/I and 0.2S at the energy meter, upstream current transformers are often designed significantly worse (e.g. 0.5 % or worse). In addition, the question arises under which criteria the energy measurement is referenced in order to comply with the above-mentioned accuracy class 0.2S at all. And this is apart from the fact that not only accuracy plays a role in power quality measurements, but also the inevitable compatibility against harmonics – one of the modern and growing main players in power quality.
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The topic of power quality is rapidly gaining importance in the context of the energy transition and smart grids and smart metering. As a result, the question marks of the supposedly affected and involved parties are piling up to the same extent. What does this mean for the distribution grid operator, the authorities, the industrial companies, the electrical inspectors, the electrical contractors, the professional associations, the infrastructure companies such as airports, railways, etc.?