Power Quality is a measure of how well a system supports reliable operation of its loads. A power disturbance or event can involve voltage, current, or frequency. Power disturbances can originate in consumer power systems, consumer loads, or the utility. Power disturbances are defined in terms of magnitude and duration. Disturbances range from transients that last for microseconds to outages that continue for hours. When a power disturbance falls outside operating limits, equipment may be disrupted or damaged.