Harmonics are produced by non-linear components and loads installed within a power system. These harmonics are characterized by a voltage drop which is not proportional to the current flow. In real-life electrical power engineering, various non-linear loads exist in components and devices, for instance, welding machines, fluorescent lighting, or electronic drive systems. You can find harmonics in private household items including, TV sets and computers.
The unfortunate thing about harmonics is that they often have adverse effects on different electrical components, such as transformers, switches, fuses, capacitors, and relays. They are known for causing detrimental effects in the form of increased losses, heating and/or excessive dielectric stresses.
If any electrical power system is being used for the purpose of telecommunications, harmonic currents may also affect the quality of signal transmission. When certain maximum levels of harmonic distortion are surpassed, electrical utilities impose high charges.
Solution to Eliminate Harmonics
Harmonics need to be removed from the system and filter reactors help in achieving this goal.
Also known as harmonic filters, they consist of reactors and capacitors. These filter reactors are installed near to the source of harmonics so that they can provide a low impedance path for harmonics currents.
This can be easily achieved by connecting filter reactors in series with a capacitor bank and forming a filter circuit tuned to the harmonics that need to be eliminated from the system.
When there are several harmonic frequencies for removal, a number of filters with different resonance frequencies are installed and connected to the bus system.
In case, a filter reactor is required to be fine-tuned, it is equipped with taps for inductance adjustment.
Problems Caused by Harmonics (No Installation of Filters) in Electrical Plants
The shape of current and voltage waveforms are considered to be ideal in the pure sinusoidal form under normal conditions. But, when the shape is distorted by harmonics, several problems start to occur. Some of them are:
- Distortion of a source voltage waveform
- Efficiency loss in transmission as well as distribution based on the RMS current increase on lines
- Failures in compensation systems
- Overheating in transformers and electrical engines
- Failures in sensitive electronic devices, PLC, and CNC devices
- Abrasions in insulation levels of equipment
- Increased losses in the overall system
- Faulty works in protection and control systems
- Increased voltage reductions
- Resonance risks in systems at high frequencies
The frequency and magnitude of these problems vary depending on various factors, such as type of facility, facility operating voltage, load type, load intensity, and grid short circuit power.
To prevent all the problems from occurring in electrical power plants and systems, filter reactors are installed in series to eliminate the harmonics component.