The third harmonic is a specific sinusoidal wave component whose frequency is exactly three times the frequency of the fundamental wave. For example, in a standard electrical power system operating on a 60 Hertz fundamental frequency, the third harmonic oscillates at 180 Hertz. In electrical engineering, the third harmonic is classified as a zero-sequence harmonic, meaning the harmonic currents produced by all three phases are in phase with one another and add up additively in the neutral conductor. This unique characteristic can lead to severe neutral conductor overloading, excessive heat generation, and potential electrical hazards if proper harmonic mitigation filters or oversized neutral wiring are not implemented.