Main Article Content
World over, the power system network has undergone restructuring process where vertically integrated utility is unbundled into generation, transmission and distribution sectors. This process has facilitated entry of private players in generation and distribution of power and introduced competitive environment in the power market. The available transfer capability (ATC) gives an assessment of probable transfer of power in the grid between different areas within the constraints of transmission system security and reliability. The estimation of ATC provides information on power transfer capability for current system condition and helps power marketers to make good decisions for power transactions between the utilities. In the proposed work, an attempt has been made to compare two methods of ATC calculation, i.e., repeated power flow (RPF) and power transfer distribution factor (PTDF) for bilateral transaction. Simulations carried out in MATLAB on IEEE 6 bus system shows that RPF is time consuming and slow. The PTDF method is then used to estimate ATC of a larger 39 bus New England test system for different system conditions of generation failure and line outage. For these conditions, critical line and critical amount of ATC is then determined.