Measurement and evaluation of power quality

Nowadays, the electrical power supply in medium-high voltage is subject to a number of changes similar to those in low voltage.

One of these main changes is the shutdown of large conventional power plants. This results in a change not only in the active power load flow, but also in the reactive power load flow. As a consequence, the reactive power compensation demand in the grid changes accordingly. In order to be able to meet the reactive power demand, reactive power compensation systems (MSCDN systems, STATCOM systems, compensation reactors and rotating phase shifters) are being installed more and more frequently.

Another change is partial cabling in the grid. Even in extra-high voltage, where in the past almost only overhead lines were considered, more and more cable sections are currently being built. These cable sections have a significantly higher capacity coating compared to an overhead line with the same operating voltage and transmission power. One consequence of these new installations is that they change the network impedance both at 50Hz and at higher frequencies. As a result, there is a risk that a shift in the network resonances will result in a worsening of the harmonic situation in the network.

Another issue is the fact that the harmonic content tends to increase in the low voltage. Although the use of transformers provides galvanic isolation between the low voltage and the medium, high and extra-high voltages, there is some transfer of harmonics between the voltage levels.

In order to be able to ensure that the above-mentioned changes do not have a negative impact on the power quality, a measurement and assessment of the power quality situation should be carried out at relevant nodes in the network at regular intervals.

Furthermore, it is advisable to document concrete measurement results of the background harmonics in the technical specification for the invitation to tender for larger plants (e.g. HVDC plants and STATCOM plants), so that the manufacturer can take a realistic preload of the grid into account in the design of the plant.

During commissioning of power electronic systems, verification of compliance with emission limits (e.g. Upost-Upre measurement) takes place to ensure that the operation of the system does not cause any inadmissible network repercussions. For this purpose, too, a measurement and assessment of the power quality is a suitable instrument to demonstrate a manufacturer-neutral evaluation of compliance with the limit values.

Our services:

We offer a wide range of measurements to evaluate the power quality and are happy to advise and support you in choosing a service package that suits your needs.

Based on our experience, we have designed ready-made service packages that are suitable for the typical occasions of a power quality measurement:

Service Package

Basic NQM1

Service Package

Advanced NQM2

Service Package

Premium NQM3

  • Basic evaluation of power quality according to EN 50160/ IEC 61000


  • Interharmonics in voltage up to 49th order


  • Upper harmonics in the voltage from 2 kHz to 9 kHz (optional)


  • Disturbance records (20 kHz time histories / 10 ms rms values)
  • All evaluations of the Basic service package




  • Harmonics in the current up to the 50th order as 10 min or 200 ms-average value (3 sec average value optional)


  • Interharmonics in the current up to 49th order


  • Harmonics in the current from 2 kHz to 9 kHz (optional)
  • All evaluations of the Advanced service package




  • Display of the time curves of the 10 min/ 3s average values of the harmonics, interharmonics, harmonics from 2 kHz to 9 kHz.


  • Detailed statistical evaluation of the recorded measured variables with the Göbel PQ-Analyzer (e.g. for statistical description of the background harmonics)

Your advantages:

  • Long experience in the field of high and extra high voltage
  • Detailed measurement and evaluation of the measurement data from one source
  • Primary-technical and secondary-technical know-how from one source
  • In-depth data evaluation with the Göbel PQ-Analyzer
  • ONE contact person for the evaluation of the complete measuring chain (transducers, sensors, PQ-measuring devices)
  • Flexible measuring concepts and the use of different measuring devices


You can find more details in our product descriptions:

We are happy to assist you in this Area.

Simply get in touch with us!