System should operate at normal frequency and voltage to maintain quals ity of supply. In the case of sensitive loads like computers, clocks. VCRs.
etc. (see Sec. 2.2.5), power quality can be defined as the relative absence of utility-related voltage variations—particularly, the absence of outages. sags, surges and harmonics as measured at the point of service(see Table 1.3). Generally, in adverse cases, the system tends to operate on low
voltage and low frequency. On low voltage, different.types of load respond differently to voltage
variation. For every one per cent drop in voltage, approximate wattage reduction will be 1.6% in filament lamps, 1.4% in fluorescent lamps and 2% in resistance loads. Induction motors draw more current, resulting in overheating and reduction in the life of the motors.insulation of motor winding may be weakened due to overheating,which may cause short circuit and burning of motors in due course. The line losses will be high due to increase in current. This will further increase the voltage drop in
the line.