The distribution system performance is measured and reported on by the network interruption performance and the quality of supply technical measures.

Network interruption performance measures comprises of reliability of supply (frequency of supply interruptions) and availability of supply (duration of the supply interruptions) technical measures that reflect how the customers are affected. Quality of supply measures show the quality of voltage level supplied to customers and comprises of voltage dips (X, T, S and Z type), voltage regulation, total harmonic distortion and voltage unbalance-related measures.

The 12-month moving average targets for these measures are based on the regulatory and operational sustainability requirements to improve the overall technical performance and customer satisfaction. Significant emphasis is placed on an integrated improvement strategy with specific short and medium term initiatives to improve the technical performance levels..

The table above provides an overview of the key distribution technical performance measures and performance. The distribution and reticulation network transformer unavailability levels are measured by the distribution supply loss index (DSLI) and reticulation supply loss index (RSLI) respectively.