Modeling of the behavior of AC undervoltage relays during voltage dips

This paper proposes a dynamic model for the behavior of an AC undervoltage protection relay during voltage dips. The behavior is expressed by means of standardized voltage tolerance curves and highly depends on the point on-wave (phase angle) of the dip initiation. Using the model, it can be explained that AC undervoltage relays are much more sensitive to voltage dips of e.g. 50% Urated than to short interruptions (0% Urated), caused by the magnetic behavior. The model takes into account the electrical, magnetic and mechanical system equations. An experimental set-up with a programmable power source as dipgenerator is build to validate the model. Finally, a complete weaving machine is represented to analyze the influence towards voltage dip immunity by adding an undervoltage protection relay