Application of steady-state harmonic distortion limits to the time-varying measured harmonic distortions

Harmonic distortion limits recommended by the majority of known standards are for the steady-state harmonics. The harmonic distortions measured in the field, however, vary with time. How to apply the steady-state limits to the actual measured harmonics has been a concern for verifying compliance to harmonic standards. In this panel paper, the problem of time-varying harmonics is examined and a solution is proposed. The proposed solution is to convert the time-varying distortion data into two magnitude-duration curves. The steady-state limits are then modified and applied to the magnitude-duration curves.