Research On Mechanical Characteristics Of Circuit Breaker Based On Force Signal Processing

Circuit breaker is an important electrical equipment in power system, which can both control and protect the grid. Since the reliability of circuit breaker has a major impact on the reliability of the power system, departments of power system pay much attention on it. Overhaul of the circuit breaker plays an important role in ensuring the reliability of the circuit breaker, and currently, the condition-based maintenance is the key direction of the repair methods. Based on the sensor technology, computer technology, and signal processing technology, the condition-based maintenance monitors the real-time parameters of the circuit breaker, and determine the present and future work status of it. Thus, overhaul can be taken before the breaker failure, to achieve preventive maintenance. In order to achieve the condition-based maintenance of circuit breaker, mechanical characteristics on-line monitoring of the circuit breaker is a very important element. This paper focuses on the mechanical characteristics on-line monitoring of VS1vacuum circuit breaker, a new method based on the force sensor and signal processing technology was carried out to accurately measure the instantaneous opening (closing) moment. With this study, a complete mechanical characteristics on-line monitoring of the circuit breaker was achieved.Firstly, in this paper, literature review on the circuit breaker was analyzed and concluded. The importance of its mechanical characteristics on-line monitoring was indicated, as well the measurement of the circuit breaker’s instantaneous opening (closing) moment. And then an improved scheme for the measurement was proposed, based on the force measurement of the switch contact and its subsequent signal processing.To validate the above scheme’s feasibility, structural models of the circuit breaker "VS1" were built in ADAMS environment. And the simulation results suggested that the instantaneous opening (closing) moment could be obtained from the force sensor’s output signal. Specifically, obvious correspondence between the instantaneous opening (closing) moment and the insulation pull arm was found, which could facilitate the following works on sensors’ output signal processing.According to the characteristics of the circuit breaker’s contact system and pull arm structures, a specific force sensor was designed, as well as its signal processing circuit. And then an experimental platform on the mechanical characteristics of the circuit breaker was set up, which could measure the main circuit parameters and the force sensor output signal. Moreover, this platform could not only realize the conventional off-line measurement systems for the mechanical characteristics, but also the on-line ones. According to test results, the previous simulation was validated, namely, the correspondence between the instantaneous opening (closing) moment and the mutation force signal in the pull arm of such circuit breaker.In order to obtain the instantaneous opening (closing) moment of the circuit breaker from the actual force signals, a developed signal processing method was proposed based on wavelet packet decomposition and signal reconstruction. Compared with the conventional off-line measurement, the method base the specific force sensor could realize lower measurement error with less than0.2ms.Lastly, the main study contents were concluded:a completed measurement system for the circuit breaker on-line monitoring was designed in this paper, which could obtain the mechanical characteristics of the circuit breaker, including its displacement, velocity, open gap, over stroke, and etc. On the other hand, the response time and the waveform of the breaker’s control circuit could also be obtained, analyzed and diagnosed.