The design of overhead lines (new lines, uprating or refurbishment) in the deregulated environment is critical to the competitiveness and profitability of the utility company. Should, for example, the design limit the power transfer to levels, which prohibit sales of MW at peak periods, the losses can be enormous. This fact, as well as the limitations imposed on capital expenditure, make the optimisation of line design a critical activity. The design of lines in the past has generally been practised with a few well-known tower, conductor and foundation combinations being used. The cost of these to the company when compared to other combinations is rarely determined. An indicator termed the “Appropriate Technology Indicator” or ATI has been developed and has been in use in Eskom, South Africa for the past 9 years. This allows for many different design combinations to be investigated and objectively compared. It has resulted in extremely competitive line designs to be developed as well as standards to be altered to the best option. Network planners can also chose the best impedance option from a wide range of conductor types. This paper describes the different aspects of line design as well as formulation of the ATI. A case study applying the ATI is also discussed with results indicating that the standard normally applied would have been the worst option of those investigated. The ATI is a tool that has manifested large benefits to line design in South Africa and can be applied in all aspects of line design be it new lines, uprating of existing lines or refurbishment of lines.
Line design, indicators, optimisation, deregulated
