The users of electric energy expect a reasonable degree of reliability and quality of service. In a broad sense, Power Quality (PQ) can be defined as “any power problem manifested in voltage, current, or frequency deviations that result in failure or disoperation of customer equipment”. Also PQ can be defined as “a set of electrical boundaries that allows equipment to function in its intended manner without significant loss of performance or life expectancy”.The users of electric energy expect a reasonable degree of reliability and quality of service. In a broad sense, Power Quality (PQ) can be defined as “any power problem manifested in voltage, current, or frequency deviations that result in failure or disoperation of customer equipment”. Also PQ can be defined as “a set of electrical boundaries that allows equipment to function in its intended manner without significant loss of performance or life expectancy”.Conditions that provide satisfactory performance at the expense of life expectancy or vice versa are not acceptable. Why should power quality be a concern to facility designers, operators, and occupants? When the quality of electrical power supplied to equipment is deficient, performance degradation results. Also, good power quality for one piece of equipment may be unacceptable for another piece of equipment sitting right next to it and operating from the same power lines, and two identical pieces of equipment can react differently to the same power quality due to production or component tolerances. Some machines even create their own power quality problems. Given such hostile conditions, it is important for an engineer entrusted with the design or operation of power systems, or manufacturing process plant to be knowledgeable about the basics of power quality.