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2 / 13 / 2024

What is total harmonic distortion? A plain-English guide to the harmful harmonics in your power system

image representing harmonic distortion

Would you drink water directly from a stream? It’s a bit risky, isn’t it? 

So why do you let electrical power enter your system unfiltered? 

Yep, the electricity coming downstream from your power company (the electricity you pay for every month) isn’t as clean as you think it is. It’s packed with what’s called harmonic distortion that’s actually dispelling a lot of that electricity before it even gets used by your system—and worse, it could be slowly damaging your equipment as you read this.

Let’s take a look at harmonic distortion, particularly in regard to how you can measure it, its impact on your system, and what you can do about it. 

What is total harmonic distortion?

Total harmonic distortion (THD), in the context of electrical systems, refers to a quantitative measure of the extent of distortion in a waveform compared to the ideal, pure sinusoidal waveform. Let’s get technical for just a second: these additional frequencies are generated by nonlinear loads like variable speed drives or certain types of electronic equipment. High THD levels indicate a greater departure from the ideal sinusoidal waveform. The bottom line: this distortion can lead to increased energy losses, reduced efficiency of power distribution systems, and potential damage to sensitive equipment. 

Total Harmonic Distortion (THD) is measured and represented as a percentage, indicating the extent of distortion in an electrical signal compared to the pure sinusoidal waveform. A low THD percentage (typically less than 5 percent) is ideal in most power systems, while a high THD percentage (5 percent or higher) indicates a significantly distorted electrical signal.

If all of this sounds a bit too technical, it can be easier to think of harmonic distortion with the concept of sound waves. When you play a musical note, like on a guitar or a piano, the sound you hear is a pure tone with a smooth, regular pattern. Now, imagine you introduce some “imperfections” or additional waves to this pure tone. These extra waves, called harmonics, have frequencies that are multiples of the original tone. This harmonic distortion changes the shape of the sound from a smooth curve to a more complex one. The sound now has extra elements that interfere with the purity of the original tone.

Negative effects of harmonic distortion

If left alone, your facility can feel the negative effects of harmonic distortion reverberate throughout the entire system. The following are just a few of the significant reasons to clean up the harmonic distortions in your system—and some of these may be problems you are already facing.

  1. Motor vibration: As harmonics distort the clean sinusoidal waveform of electrical signals, the motors in your system may experience irregular torque that leads to mechanical oscillations and vibrations. This can decrease the lifespan of your motors, increase your maintenance costs, and reduce your overall operational inefficiency.
  2. Transformer failure: Your transformers do the heavy lifting of regulating voltage and power distribution within your system. ​​The nonlinear currents introduced by harmonics can cause excessive heating that will accelerate transformer aging and potentially lead to premature failure.
  3. Capacitor bank failure: Capacitor banks are critical for power factor correction and voltage support, but harmonic distortion can cause overvoltage and overheating. This can compromise the capacitors’ insulation and overall reliability, eventually leading to failure.
  4. Cable failure: Increased currents from harmonic frequencies can lead to elevated temperatures in cables, causing insulation degradation and potential cable failures. Cable failures not only result in downtime and increased maintenance costs but can also pose major safety risks.

How to Measure Total Harmonic Distortion

Modern power meters or power analyzers are equipped with capabilities to measure and display total harmonic distortion. These devices are designed to provide comprehensive information about the quality of electrical power in a system, and THD is one of the parameters they can assess.

But knowing your THD score is just the first step. If your score is above 5 percent, the first step you need to take is installing a power quality filter that will almost instantly reduce the amount of harmonics entering in your system. At the commercial scale, harmonics filters mitigate harmonic distortions in energy to create a cleaner and more stable power supply.

The good news is that Electripure’s CleanPQ system is both a power meter that can determine your THD score for you AND a power quality filter that will clean up the harmonic distortion in your system. It’s an all-in-one solution that installs easily within your existing infrastructure and could solve many of the problems you’re currently facing in your facility. Not to mention saving you up to 20 percent on your monthly power bill right off the top. 

If you’re interested in examining your power quality, the experts at Electripure are ready to help. Sign up for a free consultation and we’ll come to your facility to help you get the full power out of the electricity you’re paying for.