The term third harmonic refers to a sinusoidal component of a periodic wave whose frequency is precisely three times that of the fundamental baseline frequency. For example, in standard electrical power systems operating on a foundational 60 Hertz frequency, the third harmonic oscillates at a frequency of 180 Hertz. In three-phase electrical power engineering, the third harmonic belongs to the zero-sequence family of triplen harmonics, meaning that the currents from all three individual phases are completely in phase with each other. Consequently, rather than canceling out along the shared return path, these currents add together directly in the neutral wire, demanding careful design considerations from electrical engineers to prevent overheating and circuit failures.