Fast switching processes in converters and switched-mode power supplies generate steep current and voltage edges. These transitions can lead to additional thermal stress, increased power losses and electromagnetic interference. Many of these effects occur sporadically and are difficult to reproduce during normal operation.

Therefore, harmonic distortion measurement should not rely on short snapshots. Effective diagnostics require a combination of long-term time series data, event recording and detailed frequency analysis to clearly demonstrate cause and effect relationships.

The advantage is clear: instead of assumptions or speculation, operators obtain measurable and verifiable data. These results support troubleshooting, warranty discussions, mitigation planning and technically documented reports.

In practice, power quality disturbances rarely appear as a single symptom. Instead, several effects usually occur simultaneously, for example:

• Overheated neutral conductors caused by harmonic currents
• Increased N-PE voltages at the end of distribution lines or socket outlets
• Unwanted tripping of protective devices
• Flickering LED lighting systems
• Audible humming or whistling from transformers or electronic equipment
• Malfunctions in sensitive IT or control systems
• Premature ageing of electronic equipment

Technically, these problems often have a similar root cause. High-frequency components propagate through cable impedances, filters, EMC components and device input circuits. These paths are not always visible in standard compliance testing. For this reason, harmonic distortion should be measured whenever new power electronic loads or generators are added to a building installation.

Harmonics are integer multiples of the fundamental frequency (50 Hz) and are typically evaluated using THD, individual harmonic components and standardized limits. Supraharmonics occur above this range, typically above 2 kHz, and are often associated with switching frequencies of modern power electronic equipment.

For practical diagnostics this means that when flickering LEDs, audible noise or touch-screen problems occur, a simple THD analysis may not be sufficient. In such cases it is necessary to measure harmonics and analyze frequency spectra in the kHz range as well.

For building diagnostics three properties are particularly important: sufficient measurement bandwidth, standards-compliant measurement methodology and reliable long-term recording. The PQ-Box ONE is particularly suitable for measurements directly at the socket outlet and can be combined with mobile analysis software.

• Optional in more complex grid connection points: PQ-Box 150 as a mobile Class A power quality analyzer for rapid disturbance source detection and flexible measurement scenarios.
• PQ-Box ONE: power quality analysis directly at the socket outlet; Class A instrument according to IEC 61000-4-30 Edition 4; suitable for measurements in low-voltage networks.
• WinPQ mobil / PQ-Box App: mobile configuration and analysis; the PQ-Box App (Android / iOS) allows wireless control of compatible PQ-Box devices via Wi-Fi.

A practical workflow for harmonic distortion analysis in buildings usually consists of three phases: measurement, evaluation and interpretation of results.

1. Measurement (precise location and sufficient duration)
   Start with a measurement directly at the affected socket outlet or at the connection point of the suspicious load such as an IT workstation, EV charger or heat pump. It is essential that the measurement captures voltage quality, harmonic distortion and supraharmonic spectra over an extended time period so that sporadic events are not missed.
2. Evaluation (frequency patterns and load correlation)
   During analysis, engineers examine whether dominant frequency components appear that match known switching frequencies of power electronic equipment. Particularly meaningful results are obtained when the disturbance frequency appears not only in the voltage spectrum but also in the current waveform of several devices. This indicates coupling effects between loads.
3. Result interpretation (verifying impact on the device)
   The key question is whether the disturbance measurably changes the behavior of the connected device. This can be demonstrated by comparing current consumption under clean supply conditions with current consumption when supraharmonic disturbances are present. If the current profile changes significantly, thermal stress increases and component lifetime may decrease.

• If harmonic distortion is measured consistently at the correct location and with sufficient recording time, typical operational benefits become visible:
• Faster root-cause identification. Instead of repeated service visits without clear findings, measurement data provides a reliable evidence base that links disturbances to specific time periods and frequencies.
• Reduced follow-up costs. Early diagnosis helps prevent premature ageing and thermal overload that could otherwise lead to equipment failure or replacement.
• Higher operational reliability. Nuisance tripping of protection devices and malfunctions of sensitive IT or control technology can be addressed more effectively because the disturbance is measured and documented rather than assumed.
• Investment security for system expansions. Before expanding EV charging infrastructure or adding photovoltaic systems, analyzing the existing power quality helps justify technical measures and avoid later damage.

If you plan to integrate or expand photovoltaic systems, EV charging infrastructure or heat pumps in your project, it is recommended to evaluate the existing power quality beforehand. Measuring harmonic distortion directly at the load provides the fastest and most reliable way to identify disturbances, derive mitigation measures and prevent consequential damage.

If you need support with measurement concepts, device selection or data evaluation, contact our team using the contact section below.