APPLICATION OF ENERGY-BASED INDEXES IN GENERATING-SYSTEM RELIABILITY-ANALYSIS

The loss of load expectation (LOLE) is the most frequently used reliability index in generating system reliability analysis. Energy based reliability indices, however, are receiving more and more attention, particularly with regard to systems that have energy limitations or with regard to systems that include intermittent sources. In this paper the use of energy based reliability indices, such as the expected unserved energy (EUE) and the energy index of unreliability (EIU), is compared with the use of LOLE in generating system reliability analysis. The comparison is made for two aspects: the minimum required capacity expansion (MRCE) if the load is increased and the load carrying capability (LCC) of intermittent sources. To compare the results of applying LOLE, EUE and EIU in generating system capacity expansion, the IEEE Reliability Test System (RTS) is used as reference. Wind turbines and photovoltaic units are added to the RTS so that the load carrying capability of these intermittent sources can be calculated. The relative differences in the computed MRCE are found to be small: less than about 10% of the expansion of the generating capacity. In the case of intermittent sources, relative differences of similar magnitude are found for the load carrying capability. It is found that the differences in MRCE caused by the use of alternative reliability indices can be related to the slope of the loss of load probability as function of the load. The difference in LCC can be related to the occurrence of hours with high load and low intermittent energy production.