Comparison of two use-of-system methods for allocating transmission supplementary cost

The use-of-system allocation methods are being accepted to allocate transmission supplementary cost. Two such methods: power flow comparison (PFC) method and generalized generation distribution factors (GGDF) method are compared in this paper. GGDF was originally developed for security evaluation, and then found useful for allocating transmission cost. This method is accepted in several papers. Like other distribution factors, GGDF considers only real power flows. However, the PFC method considers both real and reactive power flows. An example system shows that the two methods show nearly the same cost allocation if only real power flow is considered. With the inclusion of reactive power flow, the PFC method shows a cost shift among users, which is more accurate in allocating transmission cost.