Significance of an operational measure of distribution network reliability

As electrical distribution networks become more active, it is important to identify the conditions in which traditional measures of network performance still provide accurate representations of network behaviour. This work describes the development of algebraic relationships an aggregated network model, expressions for the risk to which the system is exposed under different operating periods are developed incorporating two different probabilistic representations of outage time. Comparison of these algebraic expressions is used to identify physical conditions in which an annual measure of network vulnerability may not characterise truly the network´s vulnerability within a shorter time-horizon. Results obtained from the simulation of the short term reliability of a realistic test system confirm the trends observed in the analytical studies. Together the results illustrate the potentially conservative nature of using long-term measures of reliability or risk to guide decisions regarding short-term network operation.