The paper introduces that a closing coil of breaker failed to operate during the commissiong of 110 kV Zengjiachong smart substation and analyses the operating principles of anti-bouncing circuit of breaker operating mechanism

outlet circuit in smart terminal and logical anti-bouncing and the connection among each other.By calculating the holding current

the conclusion is achieved that the fault cause was mismatch between holding current of HBJ coil in smart terminal and anti-bouncing contactor coil of breaker operating mechanism.The problem has been solved by replacing impedance paralleled with HBJ coil and the method was verified to be available.Although network has been used in smart substation

the ordinary copper cables do still exist in operating mechanism circuits and smart terminals

so the original method is still valid.The breaker and operating box are designed and manufactured by separate suppliers

and the mismatch problem still needs attention.