Estimating harmonic distortion levels for systems with random-varying distributed harmonic-producing loads

With the proliferation of harmonic-producing loads, many power distribution systems are encountering distributed harmonic sources. These sources have comparable sizes and can vary randomly. A method that can determine key probabilistic parameters of the random harmonic distortion levels in such power distribution systems is presented. The results show that the distortion indices follow a normal distribution. Since a normal distribution can be characterised by two parameters, mean value and standard deviation, a method is proposed to estimate the two parameters using commercially available harmonic analysis programs. The proposed method has been tested on three systems and the results have confirmed its validity and usefulness.