Why include Harmonic Mitigation in early phases of project designs?

Why include Harmonic Mitigation in early phases of project designs?

"Exploring truly engineered harmonic mitigation solutions early in the design process, can make a huge positive impact to the overall project capital costs and ongoing operational efficiencies.”

Why so early?


  • It’s very hard to retrofit good engineering practice in the latter stages of power engineering designs.
  • A truly engineered harmonic mitigation design at concept phase, can save enormous “re-engineering” design and construction costs when compliance requirements are only fully understood in more detail in later stages.
  • Example: A separate and flexible “group compensation” topology utilising precise active filter selections can ultimately save on physical space, improve efficiencies, enable the engineer to design to actual targets & radically change the electrical infrastructure costs.

Generic Designs vs Designs with Power Quality in Mind

Harmonic solutions are required for various technical and compliance related reasons. Once fundamental power engineering concepts are developed at the early stages of projects, they are often hard to modify as the project evolves, yet the consequences of understating the importance of harmonic mitigation topologies can have severe & lasting technical and financial implications.

Example: “Group Compensation” design using Active Filters

At Fuseco we specialise in Power Quality. We can be active participants in those crucial early concept phase discussions regarding the various harmonic solutions available. There are many techniques that can be utilised and there is room for all of those techniques when applied correctly. It's often too late at the final construction phase to transform this simplistic power engineering design below to an engineered design that carefully considers harmonics.

In the example above with many or multiple high power variable speed drives, an active filter may be the best choice. Why?

  • It can be configured to treat only what’s required of it to treat. It does this while parallel coupled to the loads. i.e. without carrying full load current of the VSD’s.
  • It can be configured to focus on one or another harmonic through individual parameter settings if required. i.e. It’s not a “blanket” overkill solution, in-line with the load.
  • Unlike Low Harmonic or Active Front Drives, if the design compliance target is based on THvD according to Australian standards, the active filter may only need to treat a portion of the harmonic current spectrum of the loads, not all of it. Additionally, if the VSD loads are a combination of duty & standby applications it would prove to be the most cost effective and most efficient total solution.
  • It is designed to meet the most stringent requirements according to AS/NZ standards & IEEE recommendations, adopted by most electrical distributors.
  • It allows more compact VSD’s to be used, compared to ones that might include passive or active in-line harmonic solutions. This can help reduce overall project costs including lowered switchroom & switchroom delivery costs.
  • With a harmonic mitigation solution separated out like this, the VSD selections can remain stable, therefore not impacting total project designs through the various project cycles and eventual project construction.

With their unique modular design and 3-level topology performance, Sinexcel Active Harmonic Filters offer a highly flexible, reliable and customisable solution in active harmonic compensation systems.

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Please contact the team at FUSECO for further information and completive pricing on the Sinexcel Active Harmonic Filter range and all your Power Quality requirements.

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In simple terms, harmonics are extra frequencies that when present in an electrical circuit, distort the AC sine wave. A harmonic of a wave is a component frequency of the signal that is an integer multiple of the fundamental frequency. For example, if the fundamental frequency is f, the harmonics have frequencies 2f, 3f, 4f... etc. 

Harmonic frequencies are equally spaced by the width of the fundamental frequency and can be found by repeatedly adding that frequency. In the case of the Australian electricity supply, the fundamental frequency is 50Hz. The frequencies of the harmonics are 100Hz, 150Hz, 200Hz, 250Hz, 300Hz, 350Hz and so on.

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For electrical systems to function in their intended manner without significant loss of performance or life, they require a supply of electricity that is of good quality. Good quality electrical power has the following characteristics: 

  • It must have a continuity of service (not be interrupted). 
  • It must have a very low Harmonic content. 
  • It must have a very low variation in the voltage magnitude. 
  • It must have very low transient voltages and currents. 

The term 'clean power' is used to describe electricity that is considered to be of good quality (see above) with particular reference to a very low harmonic content. Therefore, the term 'dirty power' is used to describe electricity that is considered to be of low quality (opposite to the above) with particular reference to a very high harmonic content. 

In Australia, our electricity is supplied in alternating current at a frequency of 50Hz. In alternating current (AC) the movement of electric charge periodically reverses direction. In direct current (DC), the flow of electric charge is only in one direction. 50Hz means that the AC has a frequency of 50 cycles per second. This is also known as the 'fundamental' frequency. AC is the form in which electricity is delivered to businesses and residences. Most electrical devices (such as motors) need clean electricity to function properly. This means that the electrical supply needs to be a clear sinusoidal wave.

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If you occasionally experience some unexplained occurrences such as flickering lights, alarms going off, or MCB's, MCCB's, RCD's and Earth Leakage devices tripping for no apparent reason, you are most likely experiencing harmonics in your electrical environment. Other signs are cables running hot, hot switchboards or overheating motors. If you are replacing your motor's bearings & insulation often, that's a strong indication of the presence of harmonics.

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Harmonics are very harmful within an electrical system and can have serious consequences. For example, the presence of harmonics reduces the life of equipment. It is possible that the investment that you made in your motors & drives will not be realised if they are damaged and need replacing before their expected life span. This can be very expensive. Harmonics cause things to run hot, which cause stress on the cables and equipment.

In the long term, this degrades an electrical system. The presence of harmonics will also mean that although you will get billed for the power that you are supplied, a large percentage of that power may be unusable. Harmonic mitigation is taking action to minimise the presence of harmonics in your electrical system and can achieve great cost savings.

Variable Speed Drives (also known as Variable Frequency Drives) are prolific creators of harmonics in electrical systems and as a result, most of the harmonic mitigation effort focuses on the input side and output side of a VFD.

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Depending on the specific situation, there are a variety of products that are used to mitigate harmonics. Fuseco's Power Quality Consultants can assist by conducting a site analysis or simply providing advice based on the details of the particular electrical system. Here is a brief summary of the product groups:

Line (input) side of the VSD

Device Features:

  • Line Reactors Simple & cost-effective method to reduce harmonics. Available in 3% & 5% versions.
  • Passive Harmonic Filters Significantly reduces harmonics from the VSD back out to the system and also improves true power factor.
  • Meets the IEEE519 Standard.
  • Active Harmonic Filters Active filters inject a 180 degree inverse current to nullify the harmonic content going back out to the system. They mitigate harmonics, compensate for voltage dips & can handle multiple VSD's relative to the reactive power required. Meets the IEEE519 Standard.

Load (output) side of the VSD

Device Features:

  • Load Reactors Simple & cost-effective method to reduce harmonics. Available in 3% & 5% versions.
  • dV/dT Filters dV/dT filters have been designed to limit peak voltage and increase voltage rise time. In addition to mitigating harmonics, the dV/dT filter also clips voltage spikes.
  • Sinewave Filters The ultimate load side harmonic mitigation product. Filters all harmonics, including reflective currents, eddy currents, common mode currents. Can be used for long cable runs (many kms). Stops the heating of cables. Great for the longevity of motors.

From the moment the AHF and SVG units were turned on our power factor issues were a thing of the past. At both sites our PF is now 0.99 on all phases all the time, the units react instantaneously to our fluctuating load and power factor and the result has been an excellent return on investment.

Brad Kilner


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