At which point is harmonic distortion least pronounced?

Harmonic distortion is least pronounced at individual nonlinear loads because at this level, the contributions to distortion are localized. Nonlinear loads such as variable frequency drives, switching power supplies, and other similar devices generate harmonics that are confined to their source. Thus, the impact of harmonic distortion is significant close to these devices but diminishes as you move away from them in the electrical distribution system.

Once you reach the main panel or other distribution points, the effects of harmonics can accumulate from multiple sources, leading to higher levels of distortion. Additionally, circuit breakers and transformers may introduce their own characteristics that can affect the quality of power, further increasing distortion levels as they interact with the harmonics created by nonlinear loads.

By assessing individual nonlinear loads in isolation, one can clearly identify and measure their specific contribution to harmonic distortion without the influence of other factors or loads. Therefore, harmonic distortion is least pronounced at these individual points, making them the optimal choice when analyzing distortion levels.