Design of the mechanical condition monitoring system for Molded Case Circuit Breakers

In this paper, a mechanical condition monitoring system of Molded Case Circuit Breaker (MCCB) is designed and developed. The operation principle of the monitoring system, the hardware design and the software design are introduced in detail. The three-phase voltage, the voltage between auxiliary normally closed contacts and the motor current are detected during the opening operation, closing operation and reclosing operation of MCCB, wherein these operations are driven by the motor. The mechanical condition characteristic parameters, including closing time, opening time, reclosing time, three phases asynchronous time, closing speed, opening speed, reclosing speed and the force on the handle, can be calculated by analyzing the voltage signals and current signals. The test results show that the system has a good performance. Moreover the characteristic parameters of circuit breaker, obtained in the test, provide test data for the theory research on remaining life prediction of MCCB.