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How do harmonics affect power quality?

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Harmonics are distortions in the waveform of alternating current (AC) power that can cause various problems for electrical equipment and devices. They are generated by nonlinear loads, such as variable frequency drives, rectifiers, inverters, and switching power supplies, that draw current in pulses rather than in a smooth sinusoidal manner. In this article, you will learn how harmonics affect power quality and what you can do to mitigate their negative impacts.

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1 What are power quality and harmonics?

Power quality is a measure of how well the voltage, current, and frequency of the AC power supply match the ideal or nominal values. Power quality issues can arise from various sources, such as voltage fluctuations, frequency variations, transients, interruptions, and harmonics. Harmonics are multiples of the fundamental frequency of the AC power supply, such as 50 Hz or 60 Hz, that are superimposed on the original waveform. For example, a 3rd harmonic is three times the fundamental frequency, a 5th harmonic is five times the fundamental frequency, and so on. Harmonics can distort the shape and amplitude of the AC waveform, creating a nonsinusoidal or distorted waveform.

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Lebon DRAN

Technicien électricien chez Prime Potomac Group
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Les courants harmoniques sont aussi causés par les charges non linéaires connectées au système de distribution. Une charge est dite non linéaire lorsque le courant qu'elle absorbe n'a pas la même forme d'onde que la tension d'alimentation. La circulation de courants harmoniques dans les impédances du réseau crée ensuite des harmoniques de tension,qui déforme la tension d'alimentation

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Shantanusinh Parmar

Matching Membership Fellow @American Physical Society | Member @I24 Space initiative
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Power quality in simplest terms is the efficiency of power, i.e. how much power is not wasted to deteriorating factors while running systems. The Power quality becomes an important decision making parameter when multiple systems are to be used together and the aim is to get the best Power Quality with the least amount of correction required. Harmonics are the non-resonant frequencies, that are on multiples of the fundamental notes of a frequency or a wave. For electricity, they refer to the non-determined AC voltages brought together by RLC factors in the circuit. Say you have 40hz, 120V supply in your socket, any voltages that are integral multiple of 40Hz, like 20Hz, 80Hz, 10Hz, 4Hz, are the harmonics of the principal frequency of 40hz.

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2 How do harmonics affect power quality?

Harmonics can have a detrimental effect on power quality, reducing the efficiency and performance of electrical equipment and devices, as well as causing malfunctioning or damage to sensitive electronic equipment. Additionally, harmonics can increase the risk of overloading and overheating of neutral conductors, due to the sum of harmonic currents from the phase conductors. Furthermore, harmonics can create resonance conditions in the power system, resulting in voltage and current amplification, overvoltages, and harmonic instability.

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Shantanusinh Parmar

Matching Membership Fellow @American Physical Society | Member @I24 Space initiative
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Harmonics are disruptive force by nature and induce parallel current and induced voltages that dampens the orignal electric signal. The way this works is that according to the principle of superimposition, the combination of two waves could result in contructive or destructive interference, that i.e lead to addition or subtraction of their peak-to-peak voltages for a net Vpp, according to their Phase differences. So, as electronics are rated for a certain power level and have voltage thresholds, higher voltages would fry them, but lower voltages can result to improper output and even an underload underload condition.

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3 How to measure harmonics and power quality?

To measure harmonics and power quality, you need to use specialized instruments, such as power quality analyzers, harmonic analyzers, or oscilloscopes, that can capture and display the waveform and the spectrum of the voltage and current signals. These instruments can also calculate and report various parameters and indicators of power quality, such as total harmonic distortion (THD), total demand distortion (TDD), power factor (PF), crest factor (CF), and flicker. You can use these measurements to identify the sources and levels of harmonics and power quality issues in your power system and to evaluate their impacts on your equipment and devices.

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Shantanusinh Parmar

Matching Membership Fellow @American Physical Society | Member @I24 Space initiative
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One could simply plug in a multimeter to the circuit and analyze the Voltages on it voltmeter. If the meter is set on AC mode and if you do not find much deflection on the reading, the system is working well without harmonics.

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4 How to reduce harmonics and improve power quality?

To reduce harmonics and improve power quality, you can use various methods and solutions. For example, choose harmonic-compatible equipment and devices, such as those with low harmonic distortion ratings, power factor correction capacitors, and harmonic filters. You can also install harmonic mitigation devices, like passive or active filters, reactors, phase shifters, or isolation transformers. Additionally, optimize the design and configuration of the power system by minimizing cable length and impedance, balancing the loads among the phases, and avoiding parallel resonance conditions. Finally, maintain good practices such as checking connections, insulation, and grounding of equipment; performing regular inspections and tests; and using power quality analyzers and software to detect and diagnose harmonics and power quality issues.

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Shantanusinh Parmar

Matching Membership Fellow @American Physical Society | Member @I24 Space initiative
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Effect of harmonics can be reduced but to compelety eliminate would require an ideal system. To decrease its effects substantially, high quality wiring, switches and Power Supply modules need to be utilized for such applications, also harmonics can be eliminated by simply adding Band pass filters of the principal frequency in the system.

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5 How to learn more about harmonics and power quality?

Harmonics and power quality are complex and dynamic topics that require a solid understanding of the theory and practice of electrical engineering. To gain a better understanding of these topics, you can read books, articles, and manuals published by IEEE, IEC, ANSI, or other reputable organizations and authors. You can also take courses, workshops, or webinars offered by universities, colleges, training centers, or online platforms. Additionally, you can consult experts, engineers, or consultants who have experience, credentials, or certifications in this field.

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Shantanusinh Parmar

Matching Membership Fellow @American Physical Society | Member @I24 Space initiative
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Any good course on Electrical system or Power Engineering provided online by Coursers, MITOCW or other such platforms would definetly involve power quality and harmonics mitigation in their curriculum.

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6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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How do harmonics affect power quality?

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6

1 What are power quality and harmonics?

2 How do harmonics affect power quality?

3 How to measure harmonics and power quality?

4 How to reduce harmonics and improve power quality?

5 How to learn more about harmonics and power quality?

6 Here’s what else to consider

Electrical Engineering

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How do harmonics affect power quality?

1

2

3

4

5

6

1 What are power quality and harmonics?

2 How do harmonics affect power quality?

3 How to measure harmonics and power quality?

4 How to reduce harmonics and improve power quality?

5 How to learn more about harmonics and power quality?

6 Here’s what else to consider

Electrical Engineering

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