What Electrical Contractors Need to Know About Harmonics (Part 2)

In his first harmonics article for PQ NewsBeat, Ross Ignall explains how harmonics can contribute to overheating, nuisance tripping, equipment faults, and other electrical problems.

In this second article, Ross explains why harmonic troubleshooting should start with dependable measurements. Total harmonic distortion, or THD, can show that distortion is present. Individual harmonic orders,  however, provide more useful information when trying to identify possible sources and equipment concerns.

He also discusses how effective troubleshooting for suspected harmonics requires more than a standard multimeter. A power quality analyzer that complies with the applicable IEC and IEEE standards reliably breaks down a distorted waveform into its individual frequency components for analysis.

The article reviews measurements such as crest factor and K-factor, along with mitigation methods that may include filters, reactors, chokes, and phase-shifting transformers.

The main takeaway: Understanding which harmonics are present, where they originate, and how they change with operating conditions gives you a stronger basis for deciding what to do next.

Read Harmonics: What Electrical Contractors Need to Know – Part 2

Frequently Asked Questions

What is total harmonic distortion in an electrical system?

Total harmonic distortion, or THD, expresses the combined harmonic content of a voltage or current waveform as a percentage of the fundamental frequency. It is useful for identifying distortion, but individual harmonic measurements are often needed for diagnosis.

What is the difference between IEEE 519 and IEC 61000-4-7?

IEC 61000-4-7 defines methods for measuring harmonics and interharmonics. IEEE 519 uses those measurement methods and establishes harmonic limits, primarily at the point of common coupling between a facility and the utility.

How should harmonic problems be corrected?

The correction method depends on the harmonic orders, their source, and the electrical system. Options can include passive filters, active harmonic filters, line reactors, chokes, and phase-shifting transformers. Measurements should guide the selection.