Interchange evaluation for electric power utilities

Three different approaches to calculating tie worth are discussed. The first approach simply involves taking the difference in production cost with and without the given interchange transaction. Next, the method of incrementals is used. Both of these approaches use B-constants in the IE (interchange evaluation) economic dispatch. The third methodology was developed in response to the consideration of an online economic dispatch which uses transmission-loss penalty factors calculated using the latest state estimator data. This methodology is based on incrementals, but instead of using B-constants, the latest penalty factors calculated from state estimator data are used for the IE economic dispatch. These methodologies were tested using data from a large-scale electric utility. It is shown that the online application of the PPD (per-unit power delivered) values for dispatch and tie-worth evaluation using the composite resistance values is feasible