Energy management + energy efficiency
Understanding harmonic profiles Too often, harmonic profiling is handled as a simple ‘box-ticking’ exercise – an approach that runs many industrial sites into trouble. Without a proper understanding of the harmonic profile across the whole installation, decisions are based on incomplete or misunderstood data. Here, John Mitchell, Global Sales and Marketing Director at CP Automation, explains why getting the profile right is essential to solving the root cause of many issues, not just the symptoms.
CP Automation is a trusted provider of power quality monitoring equipment and services in the drives, automation and power quality markets.
W here a misguided box-ticking approach is used, it very quickly becomes apparent in the numbers being used to justify harmonic mitigation. It’s not unusual to hear that a site ‘needs’ a 300-amp harmonic filter. Yet, when asked where that figure originated, it is often the case that it has been passed down from those specifying or installing the equipment. When you dig into the measurements, the data may say very little. Sometimes the calculation is wrong, sometimes it’s incomplete and sometimes it’s correct, seemingly by chance. That is the risk of not fully understanding the harmonic profile of an asset or piece of equipment. Measuring does not equate to understanding Power quality meters generate huge amounts of information, including voltage, current and frequency. However, the results aren’t always interpreted correctly. A common error is measuring a single branch of an installation, seeing current distortion rise when a particular machine runs and immediately blaming that load for the wider site issue. The bigger picture is missed. A common example is in measuring harmonics on a new machine while a variable speed drive (VSD) or HVAC system is running elsewhere on the site. Without a site-wide assessment, the distortion could be incorrectly attributed to the machine, and mitigation specified for a problem that is not actually present. When assumptions get designed in Such assumptions frequently begin at the design stage. Consultants may size a transformer and allow space for protective devices that feed power factor correction or harmonic mitigation, without carrying out a harmonic study. Those early protection and space decisions then dictate what is possible later. By the time someone realises a harmonic filter is required, the conversation becomes, “We need a 300-amp filter because the MCB is rated at 300 amps.” The actual
harmonic current on site rarely drives that conclusion. Instead, it typically reflects the fact that the upstream protection and cabling were sized early in the project, often before any harmonic analysis was carried out. Once derating is considered, that protection realistically supports only a 200 to 250-amp filter. The limitation is not technical. It is based on assumption. We have also seen sites where the harmonic filter was correctly sized for the load, but upstream protection was not. As a result, we had to limit the filter output deliberately to prevent nuisance tripping until costly retrofits could be made. Another common misunderstanding is how harmonic currents combine, because Individual harmonic components do not add directly. A long-term picture That’s why a harmonic profile is a long-term picture. What’s more, getting the full picture involves monitoring a site for around seven days, allowing for typical operation, peak conditions, worst-case scenarios and averages to be captured. From that, the correct mitigation can be specified to keep the site within relevant standards. Profiling often highlights issues beyond harmonics alone. Failed power factor correction equipment, redundant systems, and opportunities to integrate power factor correction directly into a harmonic filter can all become clear once the data is properly understood. Harmonic profiling does not have to be a one-off exercise. Fixed power quality analysers act as a continuous safeguard, showing exactly when distortion rises and what changed at that moment. This helps turn reactive troubleshooting into informed decision-making, ensuring investment is spent on the equipment that solves the root cause, not just the symptoms. CP Automation offers insights into industrial power quality, including measurement and mitigation options, to inform the right on-site engineering decisions.
For more information visit: https://www.cpaltd.net
APRIL 2026 Electricity + Control
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