A spectacular development in the use of electric energy took place in the second half of the 20th century, partly because of the growth of the petroleum industry and partly because of the establishment of large hydroelectric plants and some thermoelectric plants. The increased quantity and quality of electric energy gave rise to problems of transmission and distribution. Unlike thermoelectric plants, which may be sited where the consumer demand is greatest, sites of hydroelectric installations are not flexible, and the type of transmission lines in use has therefore changed. Although in the 1950s it was common practice to use lines with transmission voltages of less than 220 kilovolts, transmission lines were later built that could handle higher voltages. In Nigeria, for example, 330-kilovolt lines were strung; similar lines were used in Zimbabwe’s system, which feeds Harare and Bulawayo in Zimbabwe, as well as the Copperbelt in Zambia. This same system is interconnected in the north with the large Katanga (Shaba) region power stations in the Democratic Republic of the Congo. The construction of high-tension lines to supply power to the Katanga Copperbelt was completed in 1982. Much of the power for Egypt’s population centers is supplied by lines from such hydroelectric power stations as that at the Aswan High Dam. Construction of 533-kilovolt lines to transmit power from the Cahora Bassa hydroelectric station in Mozambique to South Africa was completed in 1974. The possibility of supplying landlocked states with energy from the large hydroelectric plants in the coastal states is more likely to be considered in the future.
A number of steam power stations are located in ports and cities near the coasts. The largest installations of this kind operate in Tunis, Tunisia; Casablanca and Oujda, Morocco; Dakar, Senegal; Abidjan, Côte d’Ivoire; and Lagos, Nigeria. Steam power stations using coal are by far the most common, especially in South Africa.
Electric energy consumption in large urban centers, especially when they are near coastal towns and mining areas where industrial activity has taken shape, has increased considerably. Although some countries have extended networks to the rural areas or increased the numbers of isolated low-powered stations and independent networks, progress in rural electrification has not been especially noteworthy.