What is harmonic distortion in power systems?

What is harmonic distortion in power systems?

• A. Presence of DC content
• B. Impedance mismatch causing distortion
• C. Presence of harmonics (multiples of the fundamental frequency) that distort the waveform
• D. Noise on switching of devices

Answer: (C)

Harmonic distortion means the waveform is not a pure sine because it contains harmonic frequency components—multiples of the fundamental frequency. In power systems, voltages and currents should be sinusoidal at the mains frequency. When non-linear loads or switching devices draw current in a pulsed or non-sinusoidal way, additional frequency components appear. These harmonics mix with the fundamental and distort the overall waveform, which is exactly what harmonic distortion describes. The presence of harmonics is also what’s measured by tools like total harmonic distortion (THD). Other phenomena like a DC offset, impedance-related reflections, or switching noise can occur for other reasons and do not define harmonic distortion.

Harmonic distortion means the waveform is not a pure sine because it contains harmonic frequency components—multiples of the fundamental frequency. In power systems, voltages and currents should be sinusoidal at the mains frequency. When non-linear loads or switching devices draw current in a pulsed or non-sinusoidal way, additional frequency components appear. These harmonics mix with the fundamental and distort the overall waveform, which is exactly what harmonic distortion describes. The presence of harmonics is also what’s measured by tools like total harmonic distortion (THD). Other phenomena like a DC offset, impedance-related reflections, or switching noise can occur for other reasons and do not define harmonic distortion.