Beginning in the late nineteenth and extending through the early part of the twentieth century utility frequencies ranging from 16⅔ Hz to 140 Hz were in use and utility grids were not interconnected. Eventually, 50 Hz and 60 Hz emerged as standards allowing utility grids to be interconnected and equipment design to be standardized. Other utility frequencies continue to exist, however, their use is limited to specific applications. In addition to 50 Hz and 60 Hz alternating current (AC), a few direct current (DC) distribution systems remain in parts of Argentina, India, the Madeira Islands, and South Africa.
Europe, Australia, Eastern Japan, most of Asia and Africa, along with Argentina, Bolivia, and Chile in South America utilize 50 Hz while North and Central America, Brazil, Columbia and Peru in South America, Liberia, Saudi Arabia, the Phillippines, South Korea, and Western Japan utilize 60 Hz The map shown below provides a graphical representation of this information.