Introduction to Power Quality

In recent times, due to increase in non linearity of loads and automated industrial processes, Power Quality has become a great concern for all stakeholders like utility, equipment manufacturers and end users / consumers.

Any deviation in operational performance beyond its tolerance limit, tripping or reduction of life of equipment, caused due to variation in voltage, current or frequency is termed as power quality problem.

Among all power quality problems voltage variation is the most occurring problem. It could be short duration or long duration RMS voltage variations. Voltage sag is the most common short duration voltage variation caused due to transmission system faults, with variation in magnitude and duration.

In industries about 75% of motors used are induction motors. Hence impact of voltage sag on operation of induction motor is very important study. By IEEE standard 1159 definition, the duration of voltage sag is less than 1 minute , typically of 200 -300 msec, governed by the fault clearing practices . Instantaneous response of Induction motor to voltage sag needs to be evaluated in terms of torque and speed, using dynamic equation of induction motor. Voltage sag tolerance of Induction motor can be evaluated for different magnitudes and duration of voltage sag to check its vulnerability at various loading conditions.

This course includes basics of power quality issues ,classification of RMS voltage variations, importance of voltage sag study,voltage sag characteristics,Effect of voltage sag on equipment, Voltage tolerance curves and Area of vulnerability.