Among all the faults of the circuit breaker

the mechanical fault occupies a considerable proportion. It is of great significance to take the on-line monitoring method for mechanical characteristics. This paper is devoted to the investigation of 12 kV AC medium voltage vacuum circuit breaker

develops an on-line monitoring device for it.This device is based on STM32 F407 and is equipped with RT-Thread real-time operating system

monitoring the current signal of the opening and closing coils

the angular displacement signal and the vibration signal. HNC-661 Hall current sensor was used to collect the current signal of the opening and closing coils for judging the starting time of the opening and closing operation of circuit breaker. WDD35 D4-5 kΩ angular displacement sensor is used to measure the travel-time curve of the movable contacts indirectly

contributing to the avoidance of high voltage isolation problems of linear displacement sensors. The vibration signal of the operation process of the circuit breaker is collected by the ADXL001-70 BEZ vibration sensor. After the vibration signal is processed by the short-time energy method

the opening and closing instants can be determined

and the mechanical parameter calculation is performed on this basis. This device has the functions of liquid crystal display and data uploading

and realizes online monitoring of the circuit breaker. Compared with the mechanical property tester

the monitoring data of the mechanical characteristic of this device is stable and reliable.