Network-constrained unit commitment (NCUC) is one of the most widely used applications in power system and electricity market operations. According to empirical evidence

some of the transmission constraints in a NCUC are inactive. Identifying and eliminating these inactive constraints can improve the efficiency. In this paper

an efficient method is first proposed for identifying the inactive transmission constraints. The physical and economic insights of NCUC are carefully considered and utilized. Both the generating costs and power transfer distribution factor (PTDF) are considered. Not only redundant constraints but also non-binding constraints can be identified via the proposed method. An acceleration method that combines relaxation-based neighborhood search and improved relaxation inducement is proposed for further reducing the computation time. The case study shows that the proposed method can significantly reduce the number of transmission constraints and substantially improve the efficiency of NCUC without impacting the optimality.