Induction motor behavior due to unsymmetrical and symmetrical faults

Abstract

Voltage sags are generally caused by faults on transmission and/or distribution systems. The voltage produced may be either unsymmetrical or symmetrical, depend on type of faults. Unsymmetrical fault is faults caused by single line to ground, phase to phase and two-phase faults and result in unbalanced sags. Symmetrical fault is fault due to three-phase short circuit and causes balanced sag. When the faults occur, the voltage decreases anywhere in power system, the voltage on the faulted phase goes to zero at fault location. Transformer winding connection between the fault location and motor terminal can change sag characteristics on load side and it’s also depend on type of fault. When the voltage sags occur at the terminal of an induction motor, the consequences are speed loss and current peaks may appearing at the fault and voltage recovery instants. This paper presents voltage sag characteristics caused by faults and its influence on induction motor behavior. PSCAD power system simulation was used for simple modeling and the analysis purpose.