Indices for the characterisation of bursts of short-duration waveform distortion.

Harmonic bursts are short-duration waveform distortions which result from the sudden variations in nonlinear loads; they often cause damage to common power system components. A probabilistic model is proposed that describes these disturbances in terms of suitable stochastic processes. The use of this model results in indices that can be used to characterise the system state. The indices are based on appropriate mean values of random functions which measure the quality degradation in terms of the occurrence of disturbance levels higher than a fixed value. They are particularly suited to the characterisation of the risk related to the severe burst occurrences and can allow a suitable prediction of system behaviour over time. A numerical application is presented to illustrate the physical meaning of these indices. The key feature of the proposed model is that it can be used for both burst amplitude and duration characterisation.