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Harmful Harmonics

Unsettled Waves Can Quickly Lead To Shipwreck.

Harmonics reduce the network quality, especially in the company's own network. This has negative effects on people, machines and IT. It can be really expensive, and not only in the event of a fire.

Harmonics are also called "Haromonics" because their frequency is an integer multiple of the 50-heart fundamental oscillation that we have in our power grids. Thus, they add up to bizarre rhythms in the grid and ruin the aesthetically pleasing sine wave. This is called "pollution" of the grid.

Oberschwingungen

Influence on operational safety

It would not be so bad if harmonics were not harmful to equipment and machines and even relevant for operational safety. Wouldn't IT systems be put into checkmate by them and production lines go on strike as a result. Wouldn't even standard-dimensioned neutral conductors be overloaded by harmonics and lead to cable fires? The extensive literature on this topic reads like a thriller despite its lack of popularity!

But if you have harmonics in your company network, you are not alone, because every network knows the harmonics. However, there is a need for action if there are disturbances or even dangers. The only annoying thing is that the nasty things hide themselves well and it often takes failures and more to deal with the matter.

"We had little transparency about energy consumption. But we were also concerned about operational safety. Current harmonics stress transformers and the N conductor and, in extreme cases, can lead to damage or fires in the installations."

Technician of a company in Stuttgart

From practice: Harmonics are usually measured and displayed as the total harmonic distortion in the network (THD - Total Harmonic Distortion). Here, each harmonic is represented in the magnitude of its ratio to the fundamental. The measurement below in a Stuttgart company shows a clear conspicuousness at the fourth and sixth harmonics.

But what can you do to prevent flickering light and humming fluorescent tubes from reducing the performance of your employees or to prevent motors from having to be taken to the dump prematurely due to constant heating? And what can you do to avoid having to justify yourself unpleasantly to the insurance company in the event of damage or fire? The solutions are manifold and should be well adapted to the situation. Knowing the causes, sources and effects is a good start. High-frequency measurements in the company network are important for this. A good analysis helps to evaluate and find solutions.

Modern consumers change the rules of the game

For those who are interested in more detail: The alternating current in the German transmission grid describes an almost perfect sine wave with a frequency of 50 Herz. Neither a transformer nor a light bulb, neither a heating element nor a synchronous motor have any significant influence on the sinusoidal shape. But modern consumers change the rules of the game in the grid.

Harmonics deform the required fundamental oscillation. The consequences are manifold, often even serious and expensive. Harmonics are also sinusoids with an integer multiple frequency of the 50-heart fundamental. Their frequency can therefore be 100, 150, 200, 250 ...hearts, so they add up "harmonically" to each interval of the fundamental. Because of their similarity or multiplicity to the 50-heart amplitude, one also speaks of the 2nd, 3rd, 4th, 5th to nth harmonics.

Distortions of the sine curve

The main cause for the pollution of the aesthetically pleasing sinusoidal shape is electronics, because it cannot do anything with waves, but needs a constant DC voltage. This is generated in power supplies with capacitors and other components. For this purpose, the capacitors charge themselves with a short current pulse in each wave of the fundamental oscillation. The result is distortion of the sine wave and harmonics in any variation. Switch-on processes and starting currents of machines, as well as frequency regulators and dimmers, also contribute to the contamination of the mains frequency.

Different sources of interference usually result in typical harmonics. If, for example, you want to call the consultant of your choice and the telephone system is on strike again, this could be due to harmonics of the 20th to 30th harmonic, because they like to put telephone systems out of operation!

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