Shell Technology for Development Award
The Winner: GIBB Africa
Four hundred homes in Southern African villages now have mains power, thanks to an old technique reworked by GIBB Africa. It will soon provide power for thousands more homes.
The technique is single wire, earth return (SWER): in other words, the power goes out along a single wire, mounted on simple poles with long spans, and then uses the earth as return. GIBB has shown SWER can transmit power to small users in outlying areas more cheaply than conventional transmission with three conductor wires. Eskom, the South African power company, expects to save about £10 million in 1998 by using SWER.
Power is one of the modern amenities that many South Africans yearn for. SWER means more of them can have it soon.
Householders will use the same 230-volt lighting and appliances as those supplied conventionally; but the lines that carry power to their local transformer will be SWER.
Australia and Brazil have used SWER for years to take power long distances to outlying farms. Eskom and the Botswana Power Corporation need to supply customers who are closer at hand and greater in number, but for whom they cannot justify a conventional supply.
GIBB looked at the science and showed that SWER could take higher currents and voltages than those used in Australia, and that suitable switchgear and other equipment were available. A GIBB system is able to provide 500 kilowatts of power.
The 19,000 volts of the SWER line helps overcome one of the problems of SWER, that of distinguishing the normal return flow of power through the ground from the abnormal flow when a conductor wire has fallen and needs to be repaired. The voltage, and South Africa's insulation co-ordination standards, also mean that SWER performs well even in the presence of lightning.
GIBB has further had to show it can protect people and animals from high voltages in the electrodes connecting the SWER system to earth. SWER is safer than conventional systems in one important respect. If a conductor wire breaks, the wire on the far side of the break cannot be alive and unsafe.
So GIBB was able to persuade Eskom and Botswana Power to adopt an unfamiliar technology. Botswana, which had to change its regulations on the earthing of power systems, decided on a £500,000 pilot scheme, now nearly complete, for five villages near its eastern border. It expects to use SWER for 60 more villages. Eskom, where GIBB has trained staff, expects to use SWER for more than half the 500,000 power connections it plans for 1998.
GIBB Africa, PO Box 3965, Cape Town, South Africa
Fax: 00 27 21 24 5571