Locking plug is known as NEMA connectors. NEMA stands for the National Electrical Manufacturers Association, a USA-based organization that forms a set of globally recognized and internationally applied standards for the manufacturing of electrical equipment. These standards outline the voltage and amperage configurations of plugs and receptacles to make it easier for consumers to differentiate them. NEMA connectors, including power plugs and receptacles, are among the electrical product categories covered by NEMA standards.