| Small current grounding system is widely used in distribution power systems inChina，including neutral non-grounded system and extinction-coil grounded system.The single-phase to earth faults are the most probable faults. Single-phase to earth faultdoesn’t form a short circuit loop.The fault current which caused by single-phase to earthis very small, and the system either maintain a symmetrical three-phase. So powersystem can last some time operation with single-phase to earth. If single-phase to earthlasts a long time,it will cause over voltage that effects electric equipment safety inpower system, and expand the fault,resulting in more serious fault. Because of thecharacteristics of single-phase to earth in small current grounding system and theprinciple and device of detecting fault line, finding grounding line in small currentgrounding system have not been solved. The problem of detecting fault line remains tobe further studied.Firstly，this thesis has analyzed the features of single-phase grounding fault thatoccurs in small current grounding system from two aspects of transient and steady. Onthat base, we point out colligating many methods of detecting fault line to amulti-method to detect fault line, which utilizes the technology of information fusion.Then this thesis has established a multi-method detecting fault line in small currentgrounding system, which bases on fuzzy theory. The multi-method detecting fault linecolligated three methods that include the zero-sequence current comparative method;the signal injection method and wavelet-packet transform method.Finally, with "DSP+ARM" dual-CPU system, a comprehensive line selectiondevice hardware platform and the overall software architecture has been designed,which is based on a small current grounding systems fault line selection principle andsimulation results. There is16-bit hardware-based device of TMS320F206chips andhigh-performance32-bit ARM chip LPC2214among them. This paper emphasis in thedesign process of weak signal processing ability, and the hardware device can meet theneed of data processing and signal acquisition requirements; what’s more devicesoftware is modular in design, clear in structure and easy to debug, so the project has a certain practical value. |
