Short-circuit-constrained transmission expansion planning with bus splitting flexibility

Incorporation of the short-circuit level constraints in the transmission expansion planning (TEP) has a direct impact on the final solution. Conventionally, in TEP models, a substation is tackled as a single node where are all transmission lines, power transformers, and generating units are connected to each other. However, bus splitting is a common option in most substations that divides the connected elements into two groups. Doing so, bus splitting can alter the flow path impedances and accordingly manage the short-circuit levels. Here, the short-circuit level constraints are modelled in terms of conventional TEP and bus splitting decision variables. The modelling process is very complex and some non-linear terms appear in the models. To have a tractable model in real-world problems, the non-linearities are converted to linear equivalents making the final TEP model conforming the mixed-integer linear programming format. The performance of the proposed model is examined on the 24-bus reliability test system. The results show that incorporation of the bus splitting option in the TEP problem decreases the total cost of the optimal expansion plan.