Harmonics, triplen

Triplen harmonics are third-order harmonics created by devices that draw current from the line in a non-sinusoidal waveform. These devices are known as non-linear loads and include phase-control dimmers and switch-mode power supplies.

Triplen harmonics are odd multiples of the 3rd harmonic of the fundamental (50 or 60 Hz): 3rd, 9th, 15th, 21st. etc. Triplen harmonics are of the zero-sequence variety, which means that they add rather than cancel in the neutral. This can result in neutral conductor overcurrents, as well as transformer overheating.