Some considerations on probabilistic aspects and harmonic standards

The increasing presence of current and voltage harmonics in distribution and transmission systems is well known. The harmonics are due to the wide-spread use of nonlinear loads both for efficient energy utilization in residential, commercial and industrial areas and for increasing the flexibility of power systems; they can seriously damage the system components and operation. Over the past several years electric utilities have experienced and research groups have confirmed the nondeterministic nature of harmonics, due to continual changes in system configurations, in linear load demands and in operating modes of nonlinear loads. Taking into account the time-varying nature of harmonics, it is most useful to introduce random variables and to apply probabilistic techniques of analysis