In this category, general information is shared that arises around the topic of power quality.
For some years now, one has repeatedly recognised power electronic feeders, such as photovoltaic inverters, wind turbines and battery storage systems, which show a striking similarity in the current and voltage curve shape.
What is desirable and advantageous for purely resistive consumers – namely the pure purchase of active power without fundamental oscillation and harmonic reactive power – has an unfavourable effect on the network feedback in all voltage levels for feeders of electrical energy. Because in the classical sense, the current of the connected loads – and thus the ideal sinusoidal curve shape of the voltage – is the central control parameter. This applies to large synchronous generators in power plants as well as to generators in emergency power systems and the power electronics on the secondary side of UPS systems. A synchronous generator – even a synchronous motor – will react to deviations of the voltage from the sinusoidal form with a correspondingly opposite current feed. Due to this operating principle, in simplified terms, the classic power plant generators always provide the reactive power at the fundamental frequency and at the harmonics that are demanded by the loads. This is at least within the scope of the respective design-related possibilities.
If, however, a modern power electronic feeder largely follows the voltage curve with its current control, it optimises its own frequency-dependent reactive current, but at the same time denies the grid the reactive power required by the consumers. Thus, in the worst case, it even acts as an “amplifier” of the mains feedbacks prevailing in the network. Such effects static in the frequency range and dynamic in the transient range are becoming more and more frequent.
Now, this frequency-dependent reactive power can also be provided by active, passive or hybrid filter systems. However, these possibilities already exist in purely physical terms in the designated feed-in plants. Put simply, all that is missing for this is the corresponding control parameter in the control system of such systems.
This calls for a rethink in approval and standardisation. It is of little help if the relevant standards demand the lowest possible current harmonics from feeders. It would be more helpful to promote such systems that, in addition to supporting the voltage, also participate effectively in maintaining the shape of the sine wave. Just like the good old synchronous generator in the power plant.
Measurement information can be provided in the Camille Bauer power quality meters in file format (CSV or PQDIF) using the data export scheduler. Such files can be stored locally and downloaded via the web interface or periodically or event-driven being pushed to an SFTP server.
To make events even more readable, in future users will be able to configure the output graphics with reference to a programmable recording period. This includes the RMS values ½ ≤1s before and ≤180s after the triggering of a PQ event. In addition, the sample values of ≤1s before and ≤5s after triggering can be parametrized. The events can then be zoomed directly in the web browser and allow the relevant values to be read even better in a higher resolution.
Especially during mobile measurements of power quality, it can happen that the mains voltage is briefly interrupted. Consequently, all power quality analysis units of the LINAX PQ series are now optionally equipped with a UPS and can easily withstand a power failure of 5×3 minutes.
“Electricity comes out of the socket” and why should it be of different quality? Does this mean that not all electricity is the same?
Power Quality concerns us all!
Customise compliance report with company data and logo without additional software, directly from the unit’s web browser.
Problem: Potential equalisation currents
Potential equalisation currents, often referred to as vagrant currents, are not only a problem in industrial plants. Currents can also have a disruptive effect on equipotential bonding in commercial and even residential buildings.
Cause: Leakage currents frequency inverter
The picture shows the cause of an annoying whistling in the speakers of a home stereo system. These are leakage currents of an inverter drive that must flow back to the transformer star point due to their characteristics. They always occur when a corresponding filter on the inverter is missing or defective. Common-mode voltage distortions of the phase-to-earth voltages then occur at the clock frequency at the inverter output. These clock frequency currents are then detectable at the equipotential bonding of the entire building and also at the disturbed audio system.
Solution
Retrofitting and EMC-compliant installation of an effective filter.
Impressum PQ Professionals GmbH Landsberger Straße 4 04157 Leipzig vertreten durch den GF Dipl.-Ing. (FH) Frank Strobel
Power blackout in Germany?
A warm welcome, dear friends of protection, control and electrical engineering. What actually happens during a power blackout and is that even possible in Germany? Marc Elsberg showed us a terribly realistic scenario in his book ” Blackout“. A large-scale and prolonged power blackout would have relevant consequences for our society. Let’s look at the definition, the probability and, most importantly, the actual impact of a power blackout.
Topics:
- What is a power blackout
- Blackout probability Germany
- What happens during a power blackout in Germany
- Summary
- Conclusion
Read this article from the Electrical Engineering Academy in full and click here