Phenomenon of voltage sag and swell happen directly from utility side or at customer side because of operation of certain types of equipment. Mitigation of such phenomenon is important as many of the equipments are sensitive to such conditions and may undergo irreversible damage. In recent years many novel systems for voltage sag and swell detection have been proposed albeit most of them targeted towards utility side voltage sag and swell detection and mitigation. Our present project is an attempt to develop customer side voltage sag and swell detection system based on embedded system. Again facility for automatic changeover of power source is considered to facilitate supply of clean power as long as the phenomenon exits. Hereby we present the concept, design and field results of our attempt.