TABLE OF CONTENTS Initial studies of the reliability impact of unconventional energy sources (generally renewables) have dealt with the problem only at the generation level (HLI) and have mainly centred on large-scale hydro, small-scale run-of-river hydro, and wind energy conversion systems. Very little has been done regarding generation embedded in distribution systems. The first attempts to include unconventional energy sources in reliability analysis of the generating system used the loss-of-load approach. A method which included frequency and duration concepts is presented in [28] for wind energy conversion systems. The method presented in [28] is enhanced to consider different types of units within the same wind farm [29, 30] and average wind velocity spatial correlation [30]. Another approach using the cumulant method including the failure and repair characteristic of the wind turbines is illustrated in [31]. Correlation between load and the power output of unconventional units is taken into account in [32]. Later publications use a loss-of-energy approach (LOEE). Methods based on the load modification technique were developed in [33, 34], with economic assessment included in [33]. None of these previous approaches consider explicit modelling of all the factors affecting the source of generation, e.g. wind farm, and instead treat the overall plant or farm as a single entity. The effects of the individual components and factors are therefore masked and the impact of being embedded in a weak network is generally neglected. However, some recent publications have appeared that have included these additional factors [35 39].
