International Science and Technology Journal

Voltage sags, is one of the most common power quality disturbances, that cause misoperation of an electronic and electric sensitive load such as computers, power electronic devices and programming logic controllers (PLCs), …. etc. This research paper presents new method for the classification of voltage sag types by using phase-impedance. The network simulation and protection coordination software (SIMP) was included in the CD with Digsi software introduced in this research paper to calculate the impedance (phase-to-phase and phase-to-earth) in any network points for normal mode and fault condition as well as for different types of network faults and network structures. This method is based on a comparison between the phase impedance in the load mode and the phase impedance in the electrical fault mode and gives more accurate results in classifying the voltage sag. Keywords: Voltage sags, power quality, phase-impedance, simulation and protection coordination software (SIMP), Digsi software.