Calculations > Harmonics > Harmonics: General

Harmonics occur in all electricity networks as a result of non-linear loads or sources, such as rectifiers and converters. Analysis of the network at higher frequencies enables the study of the distortion of the currents and voltages as a result of these sources and how these distortions propagate through the network.

The harmonics module has been based on a symmetrical and balanced three-phase system with balanced harmonic sources. In such network only frequencies of odd harmonic numbers occur. The harmonic multiples of 3 only exist in the zero-sequence system.

All network components like cables, loads, motors, capacitors and coils should be modelled for higher frequencies. Non-linear sources have been modelled as current injections at the loads. Shunt capacitors are modelled as part of a R-L-C filter, for which the characteristics should be specified.

The harmonics module provides insight into the behaviour of the currents and voltages at higher frequencies in the grid. Three functions are available for this: harmonic loadflow, impedance spectrum and ripple control.

•With harmonic loadflow, the behaviour of the injected harmonic currents in the grid and the consequences for harmonic voltages and harmonic distortion can be studied.

•With impedance spectrum it can be analysed which resonances in the network are to be expected.

•With ripple control, the persistence of an injected high frequency signal can be analysed on a network.