this book treats various power-quality disturbances and the way the measurements of these disturbances are processed. from the beginning, a clear distinction is made between disturbances that are continuously present (variations) and disturbances that occur occasionally (events). for each group, the origin of the disturbances is examined in detail; the extraction of information from the measurements is discussed, including advanced signal-processing techniques as well as signal-processing methods from standard documents; methods are discussed for further processing the features extracted from the signal processing into site and system indices. the authors not only examine existing material, they also cover material that is not covered in standard documents or in the scientific literature.