Impact of Transmission Line Capacity Expansion on Electricity Operation Cost and Selling Price

The reliable and cost-effective electric power system operation is one of the main drivers to keep the pace of the sustainable economic growth of a country. This paper investigates the techno economic justification of transmission line capacity expansion in the ever-increasing generation supply on the national power system grid. An optimal power flow model of the southern zone of the Power Grid Company of Bangladesh (PGCB) is developed and Lagrangian method is used to validate the model. The small test system consists of 9 buses, several generators run by 6 different types of fuel to serve the load connected through transmission lines. Using practical data set, several plausible case studies have been simulated. Focus is given on Sikalbaha-Anowara transmission line capacity expansion planning. The results show that generator operating cost and selling price of energy are 9493.32 $/Hr. and 22 $/MW-Hr. respectively despite the increasing capacity of the generator at bus 4. The simulation results show that the cost of energy reduced to 1475 $/MW-Hr. per day compared to highly congested line. This reduction is further improved to 1296 $/MW-Hr. per day for uncongested transmission line. Both the operation cost and electricity selling price is significantly reduced if the capacity of the heavily loaded line gets expanded.