Voltage quality - Harmonics

Most electrical appliances connected to the grid require a sinusoidal power supply – at 50 Hz in France. Under these conditions, so-called passive loads, such as heating resistors or capacitors, absorb a periodic 50 Hz sinusoidal current.

But some devices, most of which use power electronics, absorb a non-sinusoidal current. This current still has a frequency of 50 Hz, but it is distorted. When it crosses the network impedance, this current distorts the voltage. These disturbances are then propagated throughout the network.

These devices are said to be non-linear, producing harmonic currents and voltages.

This is known as harmonic distortion. In some cases, the network configuration can amplify harmonic distortion. In such cases, the presence of non-linear loads can lead to malfunctioning of other devices connected nearby.