Harmful harmonics

A rough swell can quickly lead to shipwreck.

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

Harmonic oscillations are also called „Haromonic“ because their frequency is an integer multiple of the 50 Hz fundamental oscillation that we have in our power grids. Thus, they add up to bizarre rhythms in the net and kill off the aesthetic sine wave. One speaks of „pollution“ of the net.

Influence on operational safety

Everything would be half as wild if harmonics were not harmful for equipment and machines and even relevant for operational safety. If IT systems were not checkmated by them and production lines would go on strike as a result. Wouldn’t even harmonics overload neutral conductors dimensioned according to standards and lead to cable fires. Despite its lack of popularity, the extensive literature on this subject reads like a detective story!

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. Annoyingly only that the nasty things hide themselves well and it must come frequently only to failures and further in order to accept itself the thing.

Practical experience: Harmonics are usually measured and displayed as the total harmonic distortion (THD) in the network. Here, each harmonic is represented in the size of its ratio to the fundamental. The lower measurement in a Stuttgart plant shows a clear conspicuity with the fourth and sixth harmonic.

„We had little transparency about the energy consumption. But we were also concerned about operational safety. Current harmonics stress transformers and the N conductor and can in extreme cases lead to damage or fires of the systems“.
(Technician of a company in Stuttgart)

But what can you do to prevent flickering lights and humming fluorescent tubes from reducing the performance of your employees, or to prevent motors from having to be put on the stockpile prematurely due to constant warming? And what is in your power not to have 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 polluter, 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

If you’re more interested: The alternating current in the German transmission network describes an almost perfect sinusoidal curve with a frequency of 50 Hz. Neither a transformer nor a light bulb, neither a heating rod nor a synchronous motor have any appreciable influence on the sinusoidal shape. But modern consumers are changing the rules of the game in the grid.

Harmonic oscillations deform the required fundamental oscillation. The consequences are manifold, often even serious and expensive. Harmonic oscillations are also sinusoidal curves with an integer multiple of the frequency of the 50 Hz fundamental oscillation. Their frequency can therefore be 100, 150, 200, 250 …heart, so they add themselves „harmoniously“ to each interval of the fundamental oscillation. Because of their similarity or diversity to the 50 heart amplitude, we also speak of the 2nd, 3rd, 4th, 5th to nth harmonics.

Distortions of the sinusoidal curve

The main cause of the contamination of the aesthetically pleasing sinusoidal shape is electronics, because it cannot do anything with waves, but requires 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. This results in distortions of the sinusoidal curve and harmonics in any variation. Switch-on processes and starting currents of machines, such as frequency controllers and dimmers, also contribute to the contamination of the mains frequency.

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

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