What are harmonics in electrical systems?

Harmonics in electrical systems refer to voltage or current waveforms that occur at integer multiples of a fundamental frequency. This means that if the fundamental frequency of an electrical system (such as the standard 60 Hz in North America or 50 Hz in many other parts of the world) is known, harmonics would be found at frequencies like 120 Hz, 180 Hz, 240 Hz, and so on.

These harmonics result from non-linear loads such as computers, sensors, and other electronic devices that draw current in a non-linear manner, distorting the sinusoidal waveform of the electrical supply. Understanding harmonics is crucial because they can lead to issues such as overheating in transformers, increased losses in the electrical system, and interference with communication lines.

The other options provided do not accurately describe harmonics. For instance, random fluctuations in voltage pertain to noise or transients rather than harmonic frequencies. Similarly, completely stable current levels do not incorporate the variations or distortions introduced by harmonics. Finally, power surges relate to temporary increases in voltage rather than the frequency components associated with harmonics. Hence, acknowledging harmonics as integer multiples of a fundamental frequency reinforces the vital role they play in understanding and managing electrical systems efficiently.