Generator contribution coefficients for pricing transmission services

The Federal Energy Regulatory Commission (FERC) in the United States has acknowledged the shortcomings of the traditional contract path method as a mechanism for implementing transmission tariffs and has encouraged the development of alternate tariff schemes. This paper presents an alternate method for determining transmission facility usage by a generator. It outlines and discusses mathematical formulae for decomposing the total real power flow that is estimated to exist in a transmission facility. The decomposition produces numerical results that express a transmission line's total real power flow as the summation of the contributions made by each generator, thereby estimating each supplier's use of the system. The technique generalizes a linear expression that is derived from assumptions similar to those used in DC load flow analysis. Each expression is unique to the dispatch on the system at the time. The technique is applied to the AC power flow solution for a modified IEEE standard 14-bus system to evaluate its accuracy on loop feeds, radial feeds and for counter flows. Each generator's contribution to the line flow is totaled and compared to the original AC load flow solution to evaluate accuracy. The results are then applied to certain flow mile topics.