Fundamentals of slow voltage variations analysis

The power quality (PQ) indicators, related to slow voltage variations, are expressed usually both absolute and relative values. Consequently, the paper presents the complete family of slow voltage variations indicators in expression of absolute, relative and percentage. The necessity of an expressive analysis of voltage variations led to idea of the voltage wave decomposition in actions and harmonics that represents a new concept of voltage variations analysis. The unitary step actions are equivalent to an infinite harmonics numbers whose interpretation detached from context, would be meaningless. In terms of electric power systems these actions are found in the interventions of the dispatcher, supplier or end-user for maintaining the rms voltage within limits. The highlighting of voltage wave levels and then the harmonic analysis of the variations which it presents is proved to be the most accurate method of slow voltage variations analysis. Also, a measurement extending upstream the point of interest represents another contribution to an expressive voltage variation analysis. Overall, the paper offers a new analysis base for causal interpretation of voltage variations in a network point of interest.