Determining a relationship between Eskom Distribution network performance improvement and infrastructure investment cost

The paper illustrates a reliability modelling approach followed by Eskom Distribution in order to better understand the relationship between the cost of network infrastructure improvements and the expected return on this investment in terms of improved reliability of the network on a system-wide basis. This is achieved by following a pragmatic sample-based approach, acknowledging that the ultimate would be to be able to model each individual feeder in a system in a simultaneous system-wide approach. Our results to date show that the most cost-effective approaches to improving reliability is not always transparent and can vary substantially between feeders and geographical locations. This is a classic illustration of the Pareto principle - in this case 80% reliability improvement for 20% of the cost. Furthermore, significant improvements in network performance may require topology changes; and there is a diminishing return on investment in terms of additional improvement in reliability for more costly infrastructure investments. The preliminary results illustrate that distribution system-wide reliability assessment is the key to optimising investments in order to provide customers more and better service in an intelligent and cost efficient way.