This paper offers a systematic literature review of real-time detection and classification of Power Quality Disturbances (PQDs). A particular focus is given to voltage sags and notches

as voltage sags cause huge economic losses while research on voltage notches is still very incipient. A systematic method based on scientometrics

text similarity and the analytic hierarchy process is proposed to structure the review and select the most relevant literature. A bibliometric analysis is then performed on the bibliographic data of the literature to identify relevant statistics such as the evolution of publications over time

top publishing countries

and the distribution by relevant topics. A set of articles is subsequently selected to be critically analyzed. The critical review is structured in steps for real-time detection and classification of PQDs

namely

input data preparation

preprocessing

transformation

feature extraction

feature selection

detection

classification

and characterization. Aspects associated with the type of disturbance(s) addressed in the literature are also explored throughout the review

including the perspectives of those studies aimed at multiple PQDs

or specifically focused on voltage sags or voltage notches. The real-time performance of the reviewed tools is also examined. Finally

unsolved issues are discussed

and prospects are highlighted.