Calculation and simulation of expected Total Harmonic Distortion

As a Power Quality specialist, HyTEPS also performs THD simulations. THD is an abbreviation of Total Harmonic Distortion. We can distinguish between THDu and THDi, where the final letter indicates distortion in the voltage (u) or current (i). THDu indicates Total Harmonic Distortion in the voltage and is one of the most important Power Quality phenomenon present in electric installations.

When changes are made to existing installations, or when there are plans to expand an installation, insight into expected harmonic distortion is particularly valuable. This is also the case with new installations. We offer you insight and advice based on our THD simulations, allowing you to take timely measures to limit harmonic distortion, thus preventing unnecessary problems and unforeseen costs.

THD simulations and calculations

Calculating THD

Total Harmonic Distortion is expressed as a percentage, which indicates how much of harmonic voltage/current is added to the fundamental (50Hz) voltage/current. It is calculated using the following formula:

Total Harmonic Distortion Formule

  • h is the harmonic order (up to the 50th harmonic);
  • X1 is the amplitude of the fundamental 50 Hz voltage or current;
  • Xh is the amplitude of the harmonic order h voltage or current.

Total Harmonic Distortion in the voltage (THDu)

Total Harmonic Distortion (THD) in the voltage (u) is directly related to the reliable functioning of electrical equipment. Several standards, such as the NEN-EN50160 / IEC61000 series, not only set limits for Total Harmonic Distortion in the voltage (THDu), but also for the maximum individual harmonic voltages. According to the EN50160 standard, THDu should not exceed 8% for 95% of the time during a given week.

Voltage wave

Subject to installation changes and expansion

In practice, THD is usually measured after an electrical installation has already been commissioned, or in the event of problems occurring within an installation. If an installation meets the standard for harmonic distortion at a certain moment, that does not necessarily mean this will always be the case; an up to date THD simulation is, therefore, recommended. In fact, complying with THDu standard limits does not ensure that everything in an electrical installation is functioning properly. From experience, we know problems such as malfunctions or failures of sensitive electrical equipment, may still occur when values are within limits set by the standard.

Many electrical installations are adjusted and/or expanded over time. For such adjustments or expansions, the effect on THD should preferably be examined. In these cases, determining THD by means of simulations offers a solution.

HyTEPS is expert in THD simulations and calculations

Take measures at an early stage

Combining professional software, previous measurements in the installation, and our technical knowledge in the field of Power Quality, we can predict what the THD value will be following a specific modification or expansion in different types of installations.

With the help of THD simulations, the necessary adjustments and measures can be taken at an early stage to keep THD within specified limits. This not only keeps harmonic distortion under control, but also helps prevent unnecessary costs.

Correct information and associated parameters are decisive for performing an accurate THD simulation. With the right information and parameters, HyTEPS determines the best approach, based on your specific situation.

HyTEPS can provide you with THD simulations


HyTEPS has the knowledge, experience and specialized equipment required to perform THD simulations. Our way of working includes a thorough analysis of the situation and testing this against applicable standards. We offer you insight and advise you on possible improvements to bring THD into the recommended ‘range’. In addition, we deliver innovative product solutions to achieve these improvements.

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