<p>Driven by the increasing integration of renewable energy, power dispatch has become a critical task in high-voltage power systems (HPS). To ensure reliable operation of the HPS, it is essential to evaluate the transmission capability of the HPS and identify feasible transmission line routings that support effective dispatch decisions. In the HPS, power capacity should be multistate since the power generators and conductors may exist in states such as complete failure, partial failure, and maintenance. Therefore, the HPS is modeled as a multistate power grid network (MPGN) in this study, where power plants, substations, and transmission lines are represented by sources, vertices, and edges, respectively. Network reliability, defined as the probability that the MPGN can successfully transmit the required power to meet demand, is adopted to assess the performance of the HPS. A novel algorithm is proposed based on the concept of minimal paths to identify all minimal power vectors, which are used not only to calculate network reliability but also to determine feasible transmission line routings. To validate the practicality of the proposed algorithm, a real-world MPGN in Taiwan is demonstrated to measure the network reliability and observe transmission line routings. Results reveal that different MPVs offer varying trade-offs between utilization and redundancy of the MPGN, which provides the administrator with practical options for dispatch planning.</p>