The advanced on-line monitoring system is applied to monitor the circuit breaker closing and opening motions and current waveform of closing and opening coil in order to obtain the running state of the spring and to monitor the spring fatigue performance at any time. It solves the problem that the spring which is the most important component in the operating mechanism is difficult to monitor in the running status. Meanwhile

some common faults

such as whether the coil is binding or the auxiliary switch is failures etc. can be judged from the current waveform of the closing and opening coil. It provides effective guarantee to reliable and safety operation of the circuit breakers.