Harmonic distortion (also called current harmonic distortion or voltage distortion ) refers to the distortion of an electrical signal, where the original sine wave is distorted by additional frequencies that are multiples of the system's fundamental frequency . This can occur in electrical networks and can negatively impact equipment performance.
What are harmonic distortions?
In an ideal electricity grid, voltages and currents have a sinusoidal waveform . This means that the voltage varies smoothly and regularly from positive to negative, at a specific frequency (for example, 50 Hz in Europe or 60 Hz in many other countries).
Harmonic distortion occurs when the current or voltage waveform is not perfectly sinusoidal, but contains additional frequencies (harmonics). These frequencies are multiples of the original frequency, such as 2x the fundamental frequency (the 2nd harmonic), 3x (the 3rd harmonic), and so on.
Example:
- In a 50 Hz network, the second harmonic would run at 100 Hz, the third at 150 Hz, the fourth at 200 Hz, and so on.
Causes of harmonic distortion:
Harmonic distortion is often caused by nonlinear loads. Nonlinear loads are devices that don't use voltage or current evenly, but instead switch rapidly or exhibit peaks in their power consumption. Examples include:
- LED lamps : The driver in LED lamps is often a non-linear load that can generate harmonics.
- Computer Equipment : Devices such as computers , printers , and servers often contain power supplies that are non-linear.
- Industrial equipment : Equipment such as motors , variable frequency drives , and welding equipment can also create harmonics due to their varying power demands.
- Solar panel and wind turbine inverters can also cause harmonic distortion due to their conversion from DC to AC.
Consequences of harmonic distortion:
Harmonic distortion can have a number of negative effects on both the network infrastructure and the connected equipment:
- Overheating :
- Harmonic currents can cause transformers, wiring, fuses and other components in the network to overheat, which can shorten the life of the equipment.
- Loss of efficiency :
- Devices may operate less efficiently due to the additional harmonic frequencies. This can lead to higher energy costs, as equipment consumes more energy than strictly necessary.
- Faults and defects :
- Devices can malfunction or fail due to harmonics disrupting their normal operation. For example, a motor can vibrate undesirably or even seize up due to harmonic distortion.
- Loss of network quality :
- The overall quality of electricity may decrease, which can cause interference with other devices on the network, such as sensitive electronic equipment.
- Reduction of equipment lifespan :
- Increased thermal stress due to harmonic currents can reduce the life of transformers, cables and other electrical components.
Solutions for harmonic distortion:
- Filters :
- Harmonic filters can be installed to filter specific harmonics from the system. This can be done either actively or passively. Passive filters reduce specific harmonics, while active filters can reduce all unwanted frequencies in real time.
- Harmonic compensators :
- These are systems that actively correct the effects of harmonic distortion, for example by balancing the current distribution in the network and neutralizing the harmonic components.
- Use of linear equipment :
- Avoiding nonlinear loads or replacing equipment that causes harmonics with more linear alternatives can help reduce distortion.
- Network designs :
- The design of an electrical network can also help minimize harmonic distortion. This may include, for example, the use of larger transformers or special switches.
- Applying filters in power supply systems of appliances :
- Many devices that create harmonics can be equipped with special filters at the input of their power supply, which reduce the distortion before it enters the network.
Summary:
Harmonic distortion in electrical systems is caused by nonlinear loads that add extra frequencies to the normal sine wave of the current. This can lead to overheating, reduced efficiency, malfunctions, and reduced equipment lifespan. It is important to monitor and control harmonic distortion, for example, by using filters and compensators or optimizing the network design to reduce its negative effects.