Exact guidelines on permissible harmonic loading apply to electric energy supply grids. This is important for both the supplier and user of the energy.
Manufacturers of electrical equipment design immunity from disturbance such that the equipment works within the permissible tolerance level. If the tolerance levels are exceeded at the point of connection, smooth electrical equipment function can no longer be guaranteed.
Harmonic currents in energy supply grids also result in increased losses and premature aging of electrical systems.
What are harmonics?
Every signal can be broken down into an addition of sine vibrations using the Fourier analysis. Alongside the basic frequency (in the German supply grid 50Hz), the total is made up of integer multiples
Typical effects which cause harmonics can be found in the power electronics of commutation processes and phase angle variation, saturation effects in transformers and gas discharges characteristic of energy-saving bulbs.
A frequency range (histogram) can be used to display the nature of harmonics compared with the fundamental oscillation.
The harmonic content states the level of signal distortion caused by harmonics. It is a ratio of the voltage's harmonic and total root-mean-square.
The harmonic content of individual harmonics is calculated from
where n is the harmonic order.
Standards focus on the 5th, 7th, 11th, 13th, 17th, 19th, 23rd and 25th harmonics. This characteristic pattern results from the wide spread of 6-pulse switch operations (power electronics where p=6 thyristors). Generally speaking, the characteristic harmonics can be established using the following formula
Restricted reactive power compensation systems and passive and active harmonic filters from PQ counteract harmonics and reliably protect your systems from overload and damage. Eliminating harmonics in the grid extends the system life and improves the quality of production.