Page 53 - Energize June 2022

TECHNICAL

Tips for mitigating harmful

harmonics

The rise of non-linear loads in industrial environments over the last two decades has resulted in the

growing problem of harmonic currents and utility-level voltage distortion. Facing a lack of awareness,
the industry has struggled to implement effective mitigation techniques.

BY JOHN MITCHELL, CP AUTOMATION

oltage distortion, caused by current harmonics can wreak havoc in a plant, damaging modulation (PWM), introduce unwanted
its equipment and the mains power supply. Damage can be serious and varied with multiples of the fundamental 50 Hz
Vthe most common symptoms including voltage notching, motor vibration, arcing on frequency in the form of harmonics.
bearings, nuisance tripping, electromagnetic interference (EMI/RFI) and overheating. Knowing what options are available to
The very first place to start is to ensure you comply with regulations. International you, can help the overall efficiency of the
harmonic control requirement, IEEE-519, limits “the maximum frequency voltage harmonic harmonic mitigation process.
to 3% of the fundamental and the voltage total harmonic distortion (THD) to 5% for systems Passive and active harmonic
with a major parallel resonance at one of the injected frequencies.” solutions can be installed in both series
Some form of filtering is subsequently recommended. and parallel (shunt) configurations within
Developing countries often have weak grids with an unreliable supply and inadequate a system. Series solutions operate in line
infrastructure, while the power ratings on products are often based on calculations with the load, meaning that units must
performed in ideal conditions. Buyers would be wise to note that these products may be sized for the full current load. Shunt
perform adversely in weak grids and may not perform to IEEE-519 standards in these units can be sized only for the harmonic
conditions. disturbance. There is a clear decision to
Remember to always stay on your toes. The last few decades have seen a rise in the be made between series-passive, shunt-
use of non-linear loads such as transistor-based variable speed drives (VSDs) and line- passive, series-active and shunt-active
commutated DC drive systems. The processes of high frequency switching and pulse width solutions.

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