Which of the following best describes the measurements used by sensors to monitor power quality?

• A. Voltage
• B. Current
• C. Power factor
• D. Harmonics

Answer: (D)

Power quality measurements focus on waveform integrity. When loads are nonlinear, they distort the voltage and current waveforms by creating harmonic content—multiples of the fundamental frequency. Sensors that monitor power quality analyze these waveforms, often using techniques like FFT, to quantify how much harmonic distortion exists (for example, total harmonic distortion and the magnitudes of individual harmonics). This harmonic information directly reflects waveform quality, which is why harmonics are the best descriptor for power quality measurements. Voltage and current alone tell you the signal levels, and power factor relates to efficiency, but neither captures the waveform distortion that defines power quality problems.