Power quality is a top priority in industries to ensure the proper operation of production systems and monitoring systems in factories. Today, harmonic distortion is a common phenomenon in electrical systems and represents an important factor in ensuring power quality. Let’s explore harmonics and their harmful effects with Tesfa through this article.
What are Harmonics?
Harmonics are unwanted distortion waves that directly harm and affect electrical power systems. In electrical systems designed to operate stably at specific frequencies (typically 50Hz), high-order wave components are generated during power transmission and blend into the electrical system due to non-linear loads. These combine with the fundamental frequency, distorting the waveform of the distribution system.
How are Harmonics Calculated?
Harmonics are characterized as multiples of the fundamental frequency. For example, in a 50Hz electrical system, the 5th harmonic will have a frequency of 250Hz, the 7th harmonic will have a frequency of 350Hz, and so on.
The total voltage harmonic distortion is the ratio between the RMS value of the voltage harmonics and the RMS value of the fundamental voltage, calculated according to the following formula:
The total current harmonic distortion is the ratio between the RMS value of the current harmonics and the RMS value of the fundamental current at maximum load or power generation mode, calculated according to the following formula:
Causes of Harmonics
The main causes of harmonics are non-linear loads in the electrical system such as high-frequency furnaces, inverters, power electronic devices, lighting systems using LED or fluorescent technology, computers, UPS systems, etc. These non-linear loads are an essential part of manufacturing plants and are the primary factors causing sine wave distortion.
Regulatory Standards
Since harmonics are an important factor that reduces the power quality of the system and causes damage to other equipment in manufacturing plants, Vietnam and countries worldwide have established many standards to evaluate the severity of harmonics. One of these standards is IEEE 519 from the Institute of Electrical and Electronics Engineers, USA, and the standard according to Circular No. TT30/2019/TT-BCT of the Ministry of Industry and Trade of Vietnam.
| Standards | Voltage harmonic distortion | Current harmonic distortion |
TT30 BCT VN | 8% | 12% |
IEEE 519 | 8% | 5% |
Harmful Effects of Harmonics
Harmonics are unwanted disturbances that directly affect power quality. They appear when using non-linear loads and severely affect equipment and machinery used in factories, including:
- Reduced motor lifespan
- Overloading circuit breakers, overheating, and causing transformer fires and explosions
- Circuit breakers, automatic switches, and fuses may trip without apparent cause
- Reduced lifespan of compensation capacitors, even causing abnormal capacitor explosions
- Causing interference affecting telecommunications equipment and automation systems
- Inaccurate operation of measuring devices
- Energy waste
- Equipment overheating and fire hazards
