The Application Of Choosing The Fault Line And Detecting The Transient Signals Based On Wavelet Transform For Single Phase-to-Grounding Fault In Small Current Neutral Grounding System

The single-phase grounding fault frequently occurs in neutral ungrounded system, the fault line and fault location must be found to avoid a phase-to-phase short as soon as possible. In this dissertation, choosing the fault line and detecting the fault location in small current neutral grounding system are summarized in detail. Subsequently, the transient course and characteristics of zero sequence capacitive current are introduced and analyzed. According to the characteristics, it is presented that the realization of choosing the fault line based on the post-fault-transient electrical quantities. The Morlet wavelet transform is applied in choosing the fault line and detecting the transient high frequency signals. The virtues and flaws in various criterions and algorithm have been compared. I have designed a simulative circuit and a hardware installation of high-speed data collection. I have completed the transmission of parallel data between 8255 and PC, and the data-sample based on the 14-bit high-speed A/D converter and DMA controller. Plenty of experiments show the real, imaginary, module and angle of wavelet transform can accurately choose the fault line and precisely identify the high frequency of transient signals.