Harmonics is a critically important concept in electronics.
Harmonics affect the quality of AC electricity delivered to homes and facilities
and the performance of equipment that uses this electricity.
Harmonics can increase energy costs and reduce the lifespan of hardware.
In some cases, harmonics can overheat electrical conductors, creating a fire risk.
In this video, we briefly explain what harmonics are, and why you should care about them.
To begin, let’s consider a mathematical concept called the periodic wave.
This is a graphical representation of a constantly
changing variable whose values follow a repeated sequence.
A familiar example is the sine wave shown on the screen.
When we examine a sine wave, one of the first things we notice is that it follows a very
symmetrical and repeated pattern.
Each full wave has a certain length, called its wavelength.
The time required for one wavelength to complete its cycle is called its period, from which
we derive the term “periodic wave.”
Periodic waves are found in a wide variety of natural phenomena, including ocean waves,
sound, and light.
Electricity transmitted over the public power grid can also be graphed as periodic waves.
A perfectly regular and symmetrical sine wave represents a very simple and “clean” example
of a periodic wave.
In the real world, however, periodic waves are subject to numerous influences that can affect
their shapes.
These can produce waves that display distortions and asymmetries, as shown on the screen.
To understand how this happens, it might be useful to work backwards and deconstruct this
wave into its constituent components.
A periodic wave, no matter how distorted, can be defined as the composite of a single
primary or fundamental wave, and one or more so-called harmonic waves of varying wavelengths.
For example, our illustration can be deconstructed into two waves, the fundamental wave and a
harmonic wave whose wavelength is one-third the fundamental.
This second wave is therefore called the third harmonic.
The combination of these two waves – the fundamental and the third harmonic – produces
the distorted wave shown in our example.
Adding additional harmonics results in further distortion in the waveform.
The presence of all these individual harmonics can be expressed as total harmonic distortion,
or THD.
The mathematical formulas for calculating THD are shown on the screen.
Fortunately, modern test instruments designed for measuring harmonics can perform these
calculations automatically and display the results, greatly simplifying the process for
monitoring THD in a facility.
In an electrical power line, a number of factors can create harmonic distortion.
These include currents introduced into the line by users of non-linear loads, environmental
causes such as lightning, electromagnetic interference, and others.
As a result, the AC electricity delivered to a facility can include a significant percentage
of THD in addition to the fundamental sinusoidal electricity produced by the power generation
plant.
The higher the THD, the more distorted the electricity’s waveform.
This can be a problem for electrical equipment designed to operate optimally when provided
with clean, undistorted AC power.
A high percentage of THD can stress electrical infrastructure and equipment, resulting in
a significant amount of electricity dissipated as excess heat.
Left unaddressed, harmonic distortion can produce numerous issues such as system underperformance,
shortened hardware life, wasted energy, and increased electrical costs.
In extreme cases, THD can increase the risk of personal injury to operators and damage
to facilities.
THD can also raise regulatory considerations.
A number of guidelines exist, such as IEEE 519-2014, that define how much harmonic distortion
is allowed for certain types of facilities.
Strict adherence to these specifications can be an essential business requirement for many
organizations.
Fortunately, there are several mitigation techniques that can minimize and even eliminate
the impact of harmonic distortion.
A first step in this process is to analyze the quality of the power in your facility.
This will help you assess how significant a problem THD is at your location, and which
measures will likely be the most effective for addressing it.
AEMC offers a full line of power quality analyzers, loggers, and meters that incorporate the most
up-to-date measurement technology and communication options.
These include the Power Quality Analyzers Models 8333, 8336, and 8435, as well as the
power and energy loggers Models PEL 102, 103, and 105.
These and other AEMC instruments, including the Clamp-On Meters Models 407 and 607, can
help you quickly and accurately perform harmonic analysis, with some models capable of automatically
measuring and displaying up to the 50th harmonic.
And many of these instruments are supported by DataView, AEMC’s data analysis software.
You can connect the instrument to a computer running DataView and view its measurement
data in real-time.
You can also download recorded data from the instrument, and format it into reports that
can be analyzed and shared.
This data can then form the basis for a comprehensive harmonics mitigation strategy.
And once this strategy is implemented, AEMC power quality instruments can help determine
how effective these measures are, and whether they require fine-tuning.
In addition, these instruments can also measure numerous other factors that can degrade power
quality.
Let’s take a moment to review some of the points we’ve covered in this video:
AC electricity produced by power plants is generated as clean, sinusoidal periodic waves.
A number of causes, both natural and man-made, can result in harmonics being added to electricity
as it is transmitted over power lines.
These harmonics distort the electricity’s waveform.
Total harmonic distortion, or THD, can have a significant impact on the operation of electrical
equipment, affecting its efficiency, reliability, safety, and cost.
And finally, AEMC offers a wide range of instruments for measuring and analyzing harmonic distortion in your facilitiy,
helping to provide the data on which an effective THD mitigation strategy
can be based.
This concludes our brief introduction to harmonics and their effects on electrical systems.
For more information about AEMC products, please visit our web site.
And be sure to check our YouTube channel for additional instructional videos about other
topics in electronics.