INTRODUCTION The issue of power quality has become very critical due to loads sensitive to power quality disturbances. Sometimes the loads themselves become the main cause of deteriorating power quality. Electronic devices such as computers, process controls and communications equipment are sensitive to disturbances in the electrical system. The effect of power quality disturbances on equipment can be considered in terms of susceptibility and vulnerability. Temporary malfunction of a device due to disturbances in the system refers to susceptibility. This phenomenon can be observed in computing devices where if the transients exceed a threshold, an error occurs. Equipment is said to be vulnerable if the electrical transient exceeds its insulation withstand level. This phenomenon can be observed in a rectifier which fails if subjected to transient voltages above a certain level. The Institute of Electrical and Electronic Engineers (IEEE) IEEE1100 standard defines power quality as "the concept of powering and grounding sensitive electronic equipment in a manner appropriate for the operation of that equipment." equipment” [2].2.2 POWER QUALITY PERSPECTIVES [26] The energy quality perspectives are as follows: • This perspective concerns the customer side of the meter. In this, the focus is on current disturbances that negatively affect equipment. • This perspective also concerns the customer side of the meter. In this regard, the equipment manufacturer must be aware of the level of power disturbances and their frequencies of occurrence in order to determine the tolerance limit of the equipment. • This perspective is that of public service. They are interested in power...... middle of paper ...... conditions.2.5.1.1 Voltage sag It is also known as voltage sag. This is one of the most common power quality problems. It is defined as a reduction in the normal voltage level between 10 and 90% of the nominal effective voltage at industrial frequency. Its duration is between 0.5 cycle and 1 minute. The magnitude of voltage drop depends on various factors such as fault type, fault location, and fault impedance. The duration over which a voltage drop occurs depends primarily on how quickly the fault is cleared by the protective device. Starting large induction motors, connecting heavy loads and faults in consumer installations can lead to a voltage drop. This can cause computer equipment to malfunction, electrical rotating machines to lose efficiency, and electromechanical contactors and relays to trip...