Even and odd harmonics in power system

1. What are odd and even harmonics?
2. What causes even harmonics in a power systems?
3. Why are harmonics odd only?
4. Why are there no even harmonics in power system?

What are odd and even harmonics?

Second-order or 'even' harmonics are even-numbered multiples of the fundamental frequencies and create a rich, pleasing sound. Third-order or 'odd' harmonics are odd-numbered multiples of the fundamental frequencies, which give the signal an edgier, more aggressive sound.

What causes even harmonics in a power systems?

Even harmonics are usually caused by so called space harmonics rather than time harmonics; i.e. asymmetries in the spatial distributions of the stator windings (due to slot spacing, for instance) rather than due to distortions in the time varying waveform of the input voltage.

Why are harmonics odd only?

Most electrical loads (except half-wave rectifiers) produce symmetrical current waveforms, which means that the positive half of the waveform looks like a mirror image of the negative half. This results in only odd harmonic values being present.

Why are there no even harmonics in power system?

The even harmonics do not normally exist in power system due to symmetry between the positive- and negative- halves of a cycle. Further, if the waveforms of the three phases are symmetrical, the harmonic multiples of three are suppressed by delta (Δ) connection of transformers and motors as described below.