Since the number of electronic devices used in systems today has increased so much, the main reason for the formation of harmonics seems to be this crowd of devices. In other words, if we are to ask why harmonic occurs, the most basic reason lying here is the modern life itself. In addition, the use of modern energy conversion techniques by that obvious increasing number of devices also creates harmonic current or current harmonics too. Under normal conditions, a mains voltage with the desired characteristics should come in the form of an interference-free and clean sine wave.
However, this is not always possible as DC power supplies are becoming more and more popular. Even the widespread use of LED lighting, especially in public spaces and buildings, causes current harmonics. If we collect all these, we can define the current harmonic as follows; sinusoidal waves other than the fundamental normal wave that disturb the voltage. Sinusodial waves are considered current harmonics and a large number of devices in a sytem can be the main reason for this.
In other words, the formation of harmonic components in the system is not a desirable situation in an electrical system. Various loads can cause this, but it needs to be measured, evaluated and prevented. With another definition, harmonic is the technical name given to the deterioration of electricity in the form of sinuses. Today, this situation can occur easily in systems that are under a lot of load, that is, it is common.
In this regard, it has become essential to be careful and prevent it. For example, electronic cards, motors and drivers, uninterruptible power supplies, fluorescent lamps may be too much for the system. Likewise, in the simplest way, harmonics are formed when a large number of computers and the equipment we have mentioned above come together. It is necessary to take professional precautions to prevent harmonic formation and to be protected from harms of it. Otherwise, transformers get overheated, devices may get damaged and mains voltage will deteriorate drastically. With the appearance of such symptoms in similar conditions, overload creates major risk factors and precautions are extremely necessary.
How Are Current Harmonics Formed?
Harmonic appears as a situation that violates the rule that the mains voltage should be in the form of a clean and interference-free sine wave. The increase in uninterruptible power supplies, namely UPS devices in public buildings, the proliferation of DC power supplies with the spread of LED lighting, or the increase of rectifier elements with power electronics may cause current harmonics.
Current harmonics can disrupt the mains voltage. There is also a natural sine wave, but disruptive harmonics cause this wave to become risky. All the elements connected to the power system and the system itself, are all open to the destructive effect of harmonics as a whole. In other words, everything in the system is about to be involved in dangerous happenings in such cases. What is required for the emergence of current harmonics on such scale that is with a negative impact on devices and the grid?
If the graphic waveforms of voltage and current differ from the sinusoidal shape, that is, a sinusoidal wave occurrence this situation becomes a problem. It is understood from the abnormal sine wave that the system has started to create harmonics. Harmonics begin to create a common problem in the industry in parallel with the developing technology. Today, such problems and the harmful effects of harmonics are in a state of increasing. Devices exposed to harmonic currents are under visible effects, especially over time.
What is the Effect of Current Harmonics on the Network?
In semiconductor elements, current and voltage waveforms are naturally distorted. However, the periodically occurring sinusoidal wave is the sum of all the waves generated. And if it accumulates, the situation becomes more dangerous. This situation may increase due to the natural state of semiconductor materials as well as the effect of certain types of nonlinear loads used in industry, such as transformers and arc furnaces. The accumulation formed as a result of sinusoidal wave repetitions outside the fundamental wave graph occurs in the harmonics.
In any case, even if all necessary and possible precautions are taken, harmonics in a network cannot be completely removed from this system. Removing harmonics from the network and removing the current harmonics and effects of the network would be difficult or even impossible. However, on the other hand, electrical devices in the systems can already operate despite the harmonic effect, unless they reach extreme dimensions. In other words, devices are immune to harmonics in normal scale. On the one hand, it should not be forgotten that working under the harmonic effect of the devices has a negative effect on the grid.
In Which Range Does Current Harmonics Create Risk to the Network?
As it is stated above, it is not possible for a network to be completely free from current harmonics and the dangers they create. Even though you try to protect your system from these effects or minimize them by taking the necessary precautions, harmonics may still occur. They create negative effect and cause problems. But, still the devices are designed to be resistant to effects caused by harmonics. So as long as the total harmonic distortion is kept below a certain level, the risk remains small and tolerable.
If the total harmonic distortion is measured by instruments and the values are below 20%, this will be a bearable limit. However, when the total data exceeds 20, device and network durability starts to break. The sum of these 220% current harmonics, which will create a dangerous situation, should be carefully monitored. In such a distortion, the fluctuation and distortion of current harmonics brings along the deterioration of the mains voltage. In case of such an exemplary situation, system fuses, even transformers and all electrical components are in danger. All these devices and assemblies can be seriously damaged; this reveals the dangerous side of current harmonics.
Levels of current harmonics (distorted waveforms) can be controlled by monitoring energy and measurement. When a risky rise in wave is observed as a result of these controls, it should be intervened. Harmonic filter applications are commonly used to prevent rising rates and protect systems from the harmful effects of harmonics. The harmonic that occurs when the alternating current, which is normally in a clean sine wave state, undergoes distortions can become very risky. The results such as too much voltage drop, increase in microprocessor errors, increase in induction counter errors are related to the harmonic. Attention should be paid to clues such as these and necessary precautions should be taken for harmonic before it causes harm to the system.
Published On - 7 December 2022