If you measure a lot, you measure crap – if you only measure parts of it, you measure crap too. The topic of “measuring grid quality” is more important today than ever before. Inverters for power generation systems, charging infrastructure for electromobility and many other electronic consumers generate grid perturbations in our voltage grid. These harmonic levels should not be ignored, as they can interfere with other consumers connected to the same grid.
A high-quality power supply is crucial for the operational reliability of modern production processes. Their power electronic drives and control systems enable considerable energy savings, optimize processes and increase productivity. However, it is precisely their load characteristics that deteriorate the power quality. Production downtimes, network failures or system defects can mean not only financial losses, but also the loss of customers. The topic of harmonics is not new, but I have to revisit it in light of current events.
Harmonics and their assessment
The power quality is assessed according to the standard and must be measured with a measuring device (mobile or stationary) of the current class A edition 3. While the first mobile measuring devices can now measure up to 150 kHz in accordance with the 61000-2-2(4) standard, the situation is different for stationary fixed measuring devices. The devices available on the market usually measure up to the 63rd harmonic. This means that the harmonics, and therefore the power quality, can be evaluated from 0.1 kHz to 3.15 kHz. This range is sufficient to be able to quantify the supply quality to be complied with by network operators in accordance with the DIN EN 50160 standard up to 1.25 kHz. For a reliable overview of the real power quality in operation, this is no longer sufficient by far.
This is because there are many consumers that emit higher harmonics, such as powerful frequency converters with clock frequencies of around 6 kHz. Inverters of generation systems such as photovoltaic systems and charging infrastructure for electromobility even have clock frequencies between 16 and 20 kHz. Measuring devices that can measure up to 3.15 kHz due to their design therefore provide a result that usually does not show the actual hazard.
Example airport
Comprehensive power quality measurements were carried out on the lighting system at a German airport by a KBR power quality expert. The halogen light bulbs here are controlled by dimmers. In addition to the expected harmonic interference in the lower frequency range, a high harmonic level was measured at 5.1 kHz. This level cannot be measured with every standard-compliant class A measuring device, as these can usually only measure up to 3.15 kHz. This limitation can lead to a misleading misinterpretation of the interference potential.
Measurement up to 20 kHz
Consumers that emit frequencies in a higher range will be increasingly used in the coming years as a result of the energy transition. This requires a corresponding adaptation of the measurement technology in order to enable a reliable assessment of the interference potential. The class A power quality measuring devices multimess D9-PQ and multimess F144-PQ from KBR were already characterized by their ability to perform measurements up to 9 kHz. Recent developments have now extended the measuring range to 20 kHz to meet current and future requirements. As a result, it is now possible to measure levels in an extended frequency band that remain hidden from most conventional measuring devices.
With this advanced extension, KBR’s devices are optimally equipped to meet the increasing challenges in the field of harmonic measurements in the future. They can therefore provide high-quality information about the interference potential that occurs and serve as reliable tools for the precise analysis and evaluation of frequency emissions.
In order to be able to measure currents up to this frequency, it is advisable to use current transformers from KBR’s multict XCTB series. These transformers have been specially developed for use in harmonic-loaded networks up to a frequency of 20 kHz.
PQ-Monitoring
In Class A-Edition 3, the state-of-the-art KBR measuring devices offer a wide range of important measured values for assessing power quality. Now it is time to evaluate these values appropriately. KBR presents its latest service: Power Quality Monitoring. With this service, the power quality measuring devices installed at your premises can be seamlessly connected. Standard reports are generated every week and sent to the user by e-mail. With just one glance – and without in-depth specialist knowledge – anyone can assess whether all values relevant to the standard and operational safety are within their limit values.
In addition, a clear heat map is sent regularly, providing a comprehensive overview of all relevant power quality parameters. This means you always have a perfect overview.
If voltage dips or interruptions occur, you will be notified immediately by e-mail. Only when individual limit values are exceeded does this require a deeper understanding of power quality. Don’t worry, because KBR has had the necessary expertise for decades. Our experienced VDE power quality experts are at your disposal to competently evaluate the measurement data and create professional measurement reports. They also develop customized solutions for your individual requirements.
You too can rely on our expertise to guarantee the quality of your energy network at the highest level. From measurement to evaluation and solution – everything from a single source.
