The paper presents a solution algorithm to improve the poor accuracy of generalised generation shift distribution factor (GGDF). A modified power transfer distribution factor (MPTDF) is used to consider the nonconformity of the demand change. Line flows can be obtained directly without running a load flow program when the system operating point is shifted to a new one. The potential performance of the proposed method is demonstrated by means of four example systems. Compared with the fast decoupled load flow (FDLF) technique, the proposed method has a much more rapid execution time and high solution accuracy. This method is very suitable for real-time application in power system operation.