The use of electromagnetic transient programs for voltage sag analysis

This paper discusses some of the modeling considerations when simulating voltage sags, and gives examples of voltage sag studies performed by using EMTP. Component models are discussed for overhead lines, underground cables, induction motors and synchronous generators. Examples are given of EMTP simulations of voltage sags due to three-phase and phase-to-phase faults. The influence of synchronous generators and induction motors on the voltage is shown. When voltage sags are only described through one magnitude and one duration, rather simple system and component models are sufficient. However, when the influence of dynamic loads, particularly induction motor loads, on voltage sags needs to be considered detailed power system modeling techniques, like EMTP, are needed.