Rational Utilization Rate Evaluation of the Transmission Network Based on the Transmission Line Total Transfer Capability

In the context of energy transition, the rapid development of renewable energy brings more uncertainty to the operation of power systems. Evaluating the rationality of the power grid planning scheme under this situation is a major challenge. The transmission line utilization rate is the key index for evaluating the utilization of transmission resources, but the traditional calculation method of transmission line utilization rate usually takes the limit transmission power of the line thermal stability as a reference, neglecting the influence of the grid operation state on transmission capacity. Therefore, it is impossible to analyze the reasons for the limited utilization of transmission resources from the index itself. The total transfer capability (TTC) of the transmission line is generally less than the thermal stability limit power under the system safety constraints. This study researches the calculation method of the transmission line TTC. Specifically, based on the optimal power flow model, the transmission line TTC under the system safety constraints from a single period and multiple periods will be calculated. Simultaneously, the corresponding linearization method was designed to reduce the difficulty of solving the model. Then, based on the transmission line TTC, an improved utilization rate index calculation method that can effectively represent the utilization level of transmission lines is proposed. Finally, transmission line TTC is discussed in the case study, and the rational utilization rate index of the transmission line is evaluated to determine the reasons for the limited utilization of transmission resources, which can verify the rationality and effectiveness of the model and method proposed in this paper.