Evaluation of transmission system usage contributions

The impact of generators and loads on transmission line flows is of much interest in competitive electricity markets. Equitable methods to set transmission usage charges in system operated in normal as well as in congested states are needed. In this paper, a method for determining the impact of generation and load values on transmission line flows has been developed to derive useful factors for allocating transmission charges. By using these factors, allocation can be attributed to generators, loads, or transaction-related net power injections. The developed procedure adopts circuit theory to evaluate individual power contributions of each generator and load on total power flowing in system lines. Derived relationships highlight dominant and opposite flows. Tested using the simple Ward-Hale six-bus test system and the IEEE 118-bus test system under a variety of operating conditions, the suggested procedure confirms the effectiveness of the proposed method to selectively assign line flow burden to generators and loads.