**2. Disturbances**

All electrical equipment may fail or malfunction when come across power quality disturbances, depending on the severity of the disturbance. It is essential for engineers, technicians, manufacturers, and power system operators to well understand and face the several power quality disturbances.

Power quality issues include voltage variations (dips, interruptions, flicker, etc.), transients (surges, lightning, and switching events), and grounding issues. **Figure 1** summarizes the common power quality problems.

**Figure 1.** The common power quality problems.

To generalize, power quality issues cover many power system problems like impulsive and oscillatory transients, different types of interruptions, voltage sags and swells, imbalance, under and over voltages, notching, noise, harmonics and interharmonics, voltage fluctuations and flickers, and power frequency variations [6]. In the following sections, these power quality problems are presented.
