For a linear load in the electrical network, the voltage used in the system and the waveform of the current generated are sinusoidal. The load characteristics of the systems used today (speed control devices, uninterruptible power supplies, etc.) are not linear. For this reason, the current shape used by the system is distorted. For example, in many industrial facilities, electric motors are controlled by motor drivers due to their advantages in control systems. Harmonic current and voltage means distortion of the voltage wavelength in power systems. Today, rapid developments in power electronics cause an increase in harmonics. In general, rectifiers and frequency inverters are sources of harmonics. In case of occurrence of harmonics, the main reason is nonlinear circuit elements used in electrical circuits. Harmonics occur in these circuit elements since the relationship between voltage and current is not linear. Arcs of lighting devices operating according to the discharge principle, over-saturation of magnetic circuits or switching the voltage in power electronics are non-linear events. Thanks to the rapid development in electronic technology, harmonic measurements can be made in a simple way. In harmonic measurement, measurements are made with fixed panel mounted or portable devices.
Measurements made with energy quality analyzers;
- Voltage values,
- Current values,
- Voltage anomalies (such as voltage drops and elevations)
- Current, voltage, power maximum minimum values
- Changes in frequency
- Changes in current and voltage waveforms
- Active power (P)
- Inductive reactive power (Qi)
- Capacitive reactive power (Qc)
- Apparent power (S)
- Power factor (PF)
- Total voltage harmonic distortion value (THDv)
- Total current harmonic distortion value (THDi)
- Individual voltage harmonics (3., 5., 7. N 51. Harmonic)
- Separate current harmonics (3., 5., 7. N 51. Harmonic)
- Data such as energy status - are obtained.
As an example of the harmonic measurements taken, two graphs are shown below. More detailed measurements are taken from the measuring devices.
Harm of Harmonics
Harmonics cause problems in supply systems and devices. If we list these major problems;
- Compensation capacitors overloaded in a very short time
- Increase of neutral current
- Heating of transformers, increasing losses
- Unspecified opening of the circuit breakers and other control systems
- Opening of the compensation stage fuses
- The formation of parasites in communication systems
- Card failures in electronic devices
- Unexpected stops in control systems and the occurrence of fault codes can be counted.
In order to avoid all these problems, measurements and analyzes related to your system should be made. The system should be handled as a complete solution and a suitable solution should be provided. These solutions;
- Passive harmonic filter applications
- Active harmonic filter applications
- Harmonic sources take various measures on the basis.
The major harmonic generating circuit elements include generators, computers, uninterruptible power supplies, electric transport systems, frequency converters, static converters, motor speed control devices, direct current power transmission, increasingly common electric vehicles and their battery charging circuits, arc furnaces, energy saving equipment, welding machines and direct current power systems. It is very important for consumers to have good quality of electrical energy. During the operation of electrical devices, loads which produce harmonics and cause some irregularities in the supply voltage are of particular importance. The distortion of voltage and current waveforms caused by harmonics in energy systems causes many problems. For example, the voltage drop is too high and this causes faults in the devices. In asynchronous motors, additional moments are created and this causes overheating. In compensation plants, the capacitors are damaged due to overload and strain. Harmonic components resonate in the network, which creates overvoltages and currents. Signal errors occur in control and protection systems. Because the harmonics result in increased currents, perforations occur in the insulation materials. Computer devices have malfunctions. Interference starts in audio and video communication devices. The measuring devices show incorrect results. Fluctuations occur in the energy transmission lines. Machines have mechanical vibrations.
Our company performs voltage harmonic measurements within the framework of electrical safety inspections in accordance with the relevant legal regulations, standards and test methods published by domestic and foreign organizations. In this regard, our company (TÜRCERT) has been accredited in accordance with TS EN ISO / IEC 17025 standard.
