Non-linear elements in the alternating current power system cause distortions in the sine wave. This distorted waveform can be written as the sum of an infinite number of sine waves of different amplitude and frequency (the frequencies of the waves must be integer multiples of the fundamental wave frequency). These calculations, called the Fourier Transform, were published in 1822 by Joseph Fourier, who worked in the field of heat conduction.

Without going into the mathematical equations of the Fourier Transform, showing it on a graph will make the subject easier to understand.

Red wave; can be written as the sum of two waves of different amplitude and frequency. The frequency of the Blue sine wave is 50Hz (fundamental) and the frequency of the Purple sine wave, the 5th harmonic, is 250Hz. The waveform of the red load current is usually not distorted like this perfection. No matter how distorted the waveform is, the result can be achieved by adding other harmonics.

Power quality measurement devices can calculate harmonics very quickly. This calculation method is known as the Fast Fourier Transform (FFT) and stands as one of the most significant algorithms of the 20th century. It is possible to make a detailed analysis of the power system and reveal the problems by examining the harmonics in the electrical system, just as doctors can diagnose via EKG.

The recommendations on harmonics, published by the Institute of Electrical and Electronics Engineers, known as IEEE, in 1992, were renewed in 2014 and were finalized as the IEEE 519-2022 Standard with the final regulation in 2022. It should be noted that while the title "Suggestion" was used in 2014, this word was changed to "Standard" in 2022. Today, it is obvious that the use of semiconductor materials in almost all electrical devices and the increase in electrification day by day have seriously triggered this change.

In the last published standard, the determination of the maximum load current, which will determine the limit values, has been changed. With the last standard, calculations will be made according to the maximum demand current (fundamental frequency) at nominal load, not a 1-year long measurement to be take from the PCC (Point of Common Coupling). In other words, there is no need for a very long time to set the limits.

According to my experience, the fact that the harmonics are within the limits does not indicate that there is no problem in the system, and that the harmonics exceed the limit levels does not necessarily indicate that a problem should occur. It should be noted that the standard specifically points to the PCC, which refers to the interaction between the customer and the electric utility. While their responsibilities to each other are specified in the standard, electrical problems in the customer's own system are a completely different issue. A customer needs to set up a energy monitoring system to solve electrical problems of their own and record measurements regularly, this is the first step towards providing the solution.

Some potential effects of harmonics:

• Electric motor malfunctions

• Increase in losses in transformers and cables

• Incorrect operation of control equipment

• Incorrect operation of the residual current relay

• Malfunctions in electronic cards

• Overloading of capacitors

• Power loss in capacitors

• Resonance risk in compensation system that without harmonic filter reactor

Tags: #Harmonics #IEE519 #Fourier #PowerSystem #ElectricalEngineering #IEEE #IEEE5192022 #PowerQuality #NetworkAnalyzer