Abstract: HPL550B2 type circuit breaker is connected in series with a spring non-charged intermediate relay normally open node in the closing circuit. When this relay is damaged, no monitoring signal is sent in the background, and the circuit breaker cannot be reclosed when the circuit is faulty. The paper deeply analyzes the potential safety hazards of failure risk in the closing circuit of this type of circuit breaker, and proposes an improvement plan. The actual field test verifies the feasibility and effectiveness of the plan, and improves the operational reliability of the equipment and system.