Developments in overhead reticulation switchgear in Southern Africa

All recent additions to the South African distribution system have been made at 22 kV and the very size of the country means that these are often long and extended in rural situations and in conditions where the lightning flash density can reach 11/12 flashes per km per year. ESKOM, the electricity supply commission, has developed a 300 kV BIL line structure as a means of combating the natural elements which beset the system. This paper describes a new range of switching and isolating devices which have been developed over the past 7 years as a means of providing equipment which is compatible with the scale of development of this network. Emphasis has been placed on such aspects as reliability, performance, cost (including that of installation) and operator safety. The challenge was to combine these aspects of performance with the vast amount of experience which has been accumulated in other areas of distribution engineering, but which has largely by-passed the development of the pole mounted devices