A classification of the power-line voltage disturbances for an exhaustive description and measurement

A classification and related terminology is suggested for the description of voltage disturbances on AC power lines. The current usage in the technical literature and in industrial and instrumentation applications has been incorporated. The disturbances are classed into two categories: waveshape disturbances and superimposed disturbances. The waveshape disturbances are further differentiated according to the type of voltage variations (over- or under-voltages) which are in turn subdivided according to a limit in time duration. The superimposed disturbances are subdivided into persistent and transient types. The former are present as a continuous voltage variation, for an extended period of time, and can be further subdivided into coherent, having a definite frequency spectrum, or random, having a continuous frequency distribution. A persistent random disturbance can be described as stationary or nonstationary, according to whether its spectrum has a statistically constant or nonconstant power density. Experimental examples of transient disturbances are presented and discussed in the light of the proposed terminology and of the physical phenomena (characteristics, origin, propagation, coupling, natural oscillations) involved.