To meet the requirements of low-latency, high determinism, and high reliability in smart substations, and to enhance adaptability to dynamic mixed traffic, this paper proposes a greedy-algorithm-based TSN-SPQ hybrid scheduling strategy. It integrates time-sensitive networking (TSN) technology with the strict priority queuing (SPQ) mechanism, and differentiates transmission paths according to message priority levels. It ensures deterministic transmission for high-priority messages while improving bandwidth utilization efficiency for low-priority traffic. A greedy algorithm is introduced to dynamically allocate time-slot windows in the TSN gate control list, prioritizing high-priority demands. This enables dynamic, conflict-free time-slot allocation and efficient bandwidth reuse under burst traffic scenarios. Furthermore, based on network calculus theory, the end-to-end delay upper bound of the hybrid scheduling strategy is rigorously derived. Simulation studies are conducted to compare the performance of different scheduling strategies. The results demonstrate that the proposed strategy significantly enhances the adaptability of smart substations to dynamic and complex traffic scenarios, providing critical technical support for their stable and reliable operation.