Based On The Resonant Grounded System Capacitive Current Detection Method Of Comparative Study

The neutral resonance grounding by arc-suppression coils has been widely utilized in mid-voltage distribution network in China. In order to rapidly and accurately extinguish arc and deal with single-phase grounding fault, high demands are put forwards in the detecting of the grounding capacitive current of network. However, most of existing detection methods has the disadvantages of low detective precision. Even more, some measurements require direct adjustment grid system’s running status, which is not conducive to the persons and the grid safety. So the research on the detection method of the capacitive current has important significance.Based on the above mentioned problems, in this dissertation, we firstly perform the comparison researching on the detection approaches of the grounding capacitive current in different ways of neutral grounding, including the neutral non-grounding and the neutral grounding by arc-suppression coils. After studying the theories of the existing approaches, the comparing and analyzing researches are performed by the simulative single-phase grounding under the MATLAB/Simulink platform, and the simulative experimental results of the commonly used methods are given. Then, the researches on the single signal injection method are performed and the simulative experiments are carried out. Based on the single signal injection method, we present an improved detection approaches based on special frequency signal injection method, in which two special frequency signals are injected in the low-voltage side. The purpose of the new method adopting vector calculation is to decrease the times of injection signal and simplify the practical operation. The signals are injected from the low voltage side of distribution network, and the capacity is calculated by measurements of the amplitude and phase of zero-sequence voltage. Apparently, the capacitance can exactly measure without operation in high-voltage side, and can realize the automatic arc-suppression control easily. The MATLAB/Simulink is utilized to build the simulation model of grid network. The simulation results under different operational situation are analyzed to prove the feasibility and accuracy of the new approach. Finally, based on the improved twice signal injection detection approach, a hardware implementation scheme based on TMS320F28335 of IT Company is presented, and the preliminary circuit modules are designed. A double T notch-filter is adopted in the analog input channel, which can deal with the problem of frequency interference, and can be helpful in improving detective accuracy. The detection results can be real-time displayed on the man-machine interaction LCD screen.