A study on probabilistic optimal reliability criterion determination in composite power system expansion planning

The optimal design of composite power system expansion planning is an important part of the overall planning task of electric power system under competitive electricity market environments. One of main keys of the successful generators and grid expansion planning comes from optimal reliability level/criteria decision, which should be given for constraint in the optimal expansion problem. However, it´s very difficult to decide logically the optimal reliability criteria of a transmission system as well as generation system expansion planning in a society. This paper approaches a methodology for deciding the optimal reliability criteria for an optimal composite power system expansion planning considering generation and transmission systems simultaneously. A probabilistic reliability criterion, LOLE_R (loss of load expectation), is used in this study. The optimal reliability criterion LOLE_R* is decided at minimum cost point of total cost curve which is the sum of the utility cost associated with construction cost and the customer outage cost associated with supply interruptions for load considering forced outage rates of elements (generators and lines) in long term forecasting. The characteristics and effectiveness of this methodology are illustrated by the case study using MRBTS size system.