Harmonics and Their Calculation
DEWETRON‘s power option has a lot to offer. Apart from its ease of use due to the sophisticated design of OXYGEN, it includes many features that prove useful during power analysis. During previous webinars, we closely examined the topic of power analysis. In course of this, we frequently heard the term “harmonics”. Therefore, we now want to add the underlying principles and give a definition to provide a whole picture.
The definition of harmonics
Harmonic frequencies (also harmonics) are voltages or currents operating at a frequency that is an integer multiple of the fundamental frequency. This means if we consider a given 50 Hz fundamental waveform, the second harmonic frequency would be 100 Hz (2 x 50 Hz), a third harmonic would be at 150 Hz (3 x 50 Hz), and so on. Similarly, if the given fundamental waveform changes to 60 Hz, the second harmonic would be at 120 Hz.
Hence, we can say that harmonics are multiples of the fundamental frequency. Therefore, we can express them more generally as 2ƒ, 3ƒ, 4ƒ, etc.
The importance of the calculation
Knowing the existence and the extent of harmonic frequencies is important as they affect the entire power system. The main consequences usually are:
- The potential amplification of some harmonics due to series or parallel resonance*
- A performance reduction of energy generation, transport, and usage systems
- The premature aging of insulation on grid components which ultimately leads to energy reduction
- Poor functioning of the system or any of its components
* Resonance is a physical effect in which several elements with specific values interact with each other and therefore oscillate and amplify a particular frequency. This amplification leads to higher energy consumption as it forces the system or some of its parts to work above their specifications. It is essential to control resonance as it can otherwise lead to the destruction of parts of the system or the entire system.
The calculation of harmonics and interharmonics
In DEWETRON’s test and measurement software OXYGEN, you can group harmonic and interharmonic frequencies to determine them up to the 1000th order. After enabling their calculation, you will see a harmonics channel for each voltage and current signal in your data channels list. In addition to that, there will be an interharmonic channel for each phase. During the calculation, OXYGEN enables you three different types of grouping:
- Grouping type “non”
Choosing the grouping type “none” means that the generation of the harmonic data only includes the frequency bin which is directly placed at the harmonic. However, the interharmonic data includes all the other bins between the harmonic bins. - Grouping “Type 1”
“Type 1” assures a grouping according to IEC 61000-4-7 standard, section 5.6. This means that the calculation considers the frequency bin directly placed at the harmonic as well as the two spectral bins next to the harmonic. The remaining bins are again input parameters for the calculation of interharmonic data. - Grouping “Type 2”
Similar to the previous type, this grouping mode again complies with IEC 61000-4-7, however, this time to section 5.5.1. In short, the harmonics calculation makes use of the entire frequency spectrum and all frequency bins. Moreover, the calculation uses all bins except for the harmonic bins to generate interharmonic data.
In the following video, our data acquisition experts exactly explain how to perform the harmonics calculation. Moreover, we prepared an article that covers the calculation as well. In case you are looking for material that covers the foundations of power analysis, we recommend this video or the related article.
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