There is tremendous increase in the number of line frequency powered electronic equipment since last five decades. About 60–70% of electric power is processed through electronic power converters in the rapid expansion of industrial, commercial, transport, residential, and military, and will eventually be 100% by next decade. The technology of power converter has brought revolution in the utility scenarios globally. The use of these power processors is not limited to automation and control but has impact on communication and information technology. All active and passive power electronic equipment employed to process power electronically basically generates unwanted electrical signals, in the form of electromagnetic noise called pollution. This electromagnetic pollution leads to performance degradation and electromagnetic interference (EMI) with other equipment or systems. Undoubtedly, this EMI would ever increase, unless EMC standards are enforced mandatory to follow major compatibility limits. The first part of the chapter reviews the mechanisms that lead to the generation of EMI signals through power electronic equipment and introduces the various noise types along with their propagation mechanisms. Also, the problems caused by the various noise types are presented. An overview of the standards will follow. Further, a brief discussion about various noise mitigation techniques and their evaluation has been presented with emphasis on line harmonics reduction.