Study On Single-Phase-to-Ground Fault Line Selection Device For 10kV Outlet Of Substation

In China, small current grounding of transformer neutral point operation mode it is widely used in low voltage distribution grid. Especially in the lOkV power grid with 10kV substation, arc suppression coil grounding is the most used at the neutral point grounding method. However, due to different geographical characteristics and load characteristics, there are still some places where use the neutral ungrounded mode of operation. Some of the existing line selection device only for a single grounding mode fault line selection, and its use of the line selection algorithm is also more simpler. This leads to the low reliability of the line selection device and the large error of line selection. Based on this situation, thesis designs the single-phase-to-ground fault line selection device for substation 10kV outlet line.First of all, the fault characteristics of the two systems are analyzed in detail by simplifying the steady-state and transient equivalent circuit for the neutral point ungrounded system and the neutral point by the arc suppression coil grounding system. Furthermore, the energy method, the fifth harmonic method and the wavelet analysis method are used as the basis of the line selection algorithm. The principle of the above three algorithms is introduced in detail, and the selection criteria of each algorithm are constructed respectively. On basis,the process of comprehensive route selection is discussed in detail. And further using Matlab to build a lOkV circuit simulation model, and were extracted fault information required for each algorithm.Through the analysis and comparison of the characteristics of the fault information to verify the algorithm, and achieved good experimental results.Finally, the hardware and software design of the device are given. In terms of hardware, due to the requirements of the complex line selection algorithm, this device uses the ARM + DSP structure. Taking ARM chip STM32F103ZET6 as the core to form the line control module, the data acquisition and processing module is composed of DSP chip TMS320F28335 as the core processor. Software is given the overall line selection process, and was drawn two modules of the main program flow chart.