3. Effects

In the presence of harmonics, the true RMS value of the signal is greater than the RMS value of the fundamental alone (figure 3 ). Devices (such as circuit breakers) designed for a given fundamental current may then be subject to severe additional stress.

The best-known effect of harmonics is the destruction of capacitors or circuit breakers in the event of resonance. Another frequent phenomenon in low-voltage networks is the heating of neutral conductors under the effect of rank 3 harmonic currents.

Harmonics can also have less visible, but just as real, effects in the form of accelerated equipment fatigue. We therefore distinguish between instantaneous and long-term effects.