An overview of voltage sag theory, effects and equipment compatibility

In the modern industrial world, many electronic and electrical control devices are part of automated processes, to increase energy efficiency and productivity. Due to the fact that most of these devices are designed with the use of modern power electronics, they are characterized by an extreme sensitivity on power quality variations. This paper describes an overview of the theory and effects of voltage sag. Reference to non-rectangular events, and the procedure to evaluate the power systems performance regarding voltage sag, through using particular indices to assess equipment compatibility issues is presented.