Abstract: This paper analyzes and optimizes a logic design flaw identified in a specific nuclear power unit under particular switchyard operating conditions. During maintenance on a 500kV single-busbar in the switchyard, with one unit operating in a configuration where its generator is connected solely via a 500kV tie breaker, a single-phase autoreclosure of that tie breaker can induce a transient process. This transient may trigger a spurious actuation of the Turbine Overspeed Protection Control (OPC), which employs a "one-out-of-three" voting logic. The false OPC signal causes a power mismatch between the primary and secondary circuits, leading to a sharp pressure drop in the steam generator header. This drop activates the S-signal, indicative of a significant event, ultimately resulting in a reactor trip, containment isolation, and the inadvertent initiation of passive engineered safety features (including safety injection and core makeup tanks). To eliminate this risk, this paper proposes an optimization to the OPC logic, thereby enhancing the operational reliability of the unit under such special conditions.