Distribution Network Grounded Fault Signal Acquisition System Based On μC/OS-Ⅱ

With the development of economy and society, the electricity power consumption is increasing. Distribution network fault affects the quality of electricity power supply, and even cause power outages. The statistical data from electric company shows that a large part of the distribution network fault is caused by ground fault. In order to restore power supply quickly and minimize the negative impacts of distribution network fault, it is necessary to use fault diagnosis device to detect the fault line. Accurate and rapid acquirement of zero sequence voltage and zero sequence current signals when the fault occurred are the basis of faulty lines electing by fault diagnosis device.This paper mainly studies a system which collects and uploads data of zero sequence voltage and zero sequence current signals from the distribution lines. The system comprises eight collectors and CAN Bus. Each collector can upload the collected data to fault diagnosis device through the CAN Bus. Though analyzing the characteristic of the fault signals (zero sequence voltage and zero sequence current signal), a method for collecting transient fault signals is suggested. According to the requirements of this method, acquisition system hardware have been designed. The μC/OS-Ⅱ operating system have been modified and transplanted in the hardware. Communication protocols for uploading data to the fault diagnosis device have been made. Software of acquisition system has been written to realize collection and uploading.Through laboratory test, the fault signals which are simulated have been collected and uploaded to the fault diagnosis device by acquisition system. The signal waveforms which show on fault diagnosis device are consistent with the fault signal waveforms which simulation on MATLAB. According to the upload data, the fault line is selected exactly by fault diagnosis device. This suggests that acquisition system have collected and uploaded the zero sequence voltage and the zero sequence current signals when the fault occurs.In the transformer substation, data which were collected by the acquisition system can accurately indicate zero sequence current from each distribution lines and the zero sequence voltage from bus, and transient fault signals can be captured completely when grounding fault occurs. The fault diagnosis device can accurately select the fault line based on the acquired data, which indicates the acquisition system can be applied on faulty line selection.The acquisition system can capture both grounded faulty transient signals and stationary signals, and upload data to the fault diagnosis device. The uploaded data can be used as criterion for the fault diagnosis device.