Sub-transmission substation expansion planning (SSEP) considering load uncertainties using a new clustering method

The adequate design of sub-transmission system leads to efficient economical and technical planning. However, the fast growth of electrical networks has brought more uncertainties to the planners. Failure in considering the uncertainties of both the size and location of load centers in substation expansion planning (SEP) may cause various consequences such as reliability problems. This research proposes a new possibilistic mathematical approach to cover uncertainties of load locations as well as load sizes in the sub-transmission substation expansion planning (SSEP) problem. The site and capacity of the desired substations and MV feeders are determined through the approach for the planning years. Fuzzy functions of load sizes and load locations are put into the clustering method in the expansion planning. Accordingly, mathematical clustering is modified by fuzzy arithmetic. Unlike existing heuristic and metaheuristic techniques, the proposed method is finitely convergent to a solution. A test, along with a real system, is used to demonstrate the functionality of the presented approach. Comparison of energy not supplied (ENS) costs adding to investment costs in different cases considering DG installations, indicates that compared with traditional methods, the new method has improved the expansion planning result.