Study On The Current And Voltage Dynamical Monitoring System Of The Miniature Circuit Breaker

The contact is the execution unit of the miniature circuit breaker. The voltage and currentwave on the contact is the most direct reflection of the circuit breaker’s operating performanceand protection features. During the miniature circuit breaker’s breaking process the waveform ofthe current and voltage on the contact will dynamically change. And the waveform can not onlyreflect the dynamical behavior of the contacts, but also reflect the phenomenon of the arcing andcontact wear. Therefore, it will contribute to research the electrical and mechanical wear on thecontact, the performance degradation of the circuit breaker to study the current and voltagewaveform monitoring technology on MCB contact. It has a very important significance. Thisarticle mainly studies the dynamical monitoring technology of the MCB contact voltage andcurrent. And then further study the calculation method of the arcing energy.First, conduct research on the hardware part of the MCB contact current and voltagedynamic monitoring system. The hardware of the test system is mainly consisted of: the analogload control circuit, the data acquisition circuit and the detection circuit of the voltage andcurrent. In the analog load control circuit, ACSSR is used as a high-speed switching device sothat it can switch the multiple resistances quickly to produce the desired current. The detectioncircuit of the voltage and current consists of filter circuit and sensors which have a shortresponse time, high precision, high linearity and wide frequency range. The detection circuittakes parallel measurement on contact voltage by two sensors which have different ranges toensure the measurement accuracy of the contact’s voltage in the entire range. The dataacquisition circuit selects Advantech PCI-1742U cards for high-speed sampling and transmitteddata in high-speed by DMA.Second, conduct research on the software part of the MCB contact current and voltagedynamic monitoring system. The software of the test system is designed by LABVIEW,including the control program of the analog load, the data collection procedures and the program of data processing (display and storage). In the control program, the system controls the ACSSRactions through the operation on I/O ports of the PCI-1750to produce the test current that isdesired by contact load circuit. In the data acquisition and processing program the Producer-Consumer structure mode is adopted, which carries out the high-speed data acquisition andprocessing synchronously and it can prevent the loss of the sampling points effectively. The dataacquisition program is compiled in the producer cycle to sample the contact signals at a highspeed. The data processing program is compiled in the consumer cycle, which makes themonitoring system sample signals at the speed of750k/s. Due to the large amount of the dataand high sampling speed in the test system, TDMS data stream format is used to save relateddata.In addition, according to the relevant reference material, the project puts forward thecalculation method of arc time and further calculates the miniature circuit breaker’s contactarcing energy under different currents.