Small Current Grounding System Single-phase Fault Line Selection And Ranging

Neutral un-effectual grounded system is widely used in the distribution networks in China. It has the virtue of proving power supply's reliability. Since Single phase earthed faults accounts for more than 80% of the total faults in the grid, it is crucial to select the fault circuit and set out the location of the fault point. But till now fault selection and fault location when single-phase permanent earthing appears haven't been solved ideally.At first, the paper analyzes the steady and transient procedure in the non-effectively grounded system when single phase earthed fault occurs. Special attention is paid to the transient procedure of Peterson coil grounded system after faults. Then, it introduces the basic principle of the wavelet analyzation and its application in power systems. In the viewpoint of the digital signal processing, we use the wavelet to help select the fault. Transient components are extracted from the fault signal by the means of the wavelet analyzation. Subsequently the comparision is conducted in the aspects of gate value, magnitude and the polarity.This paper studies single-phase earthing fault selection and fault location in the non-effectively grounded system. By means of the simulation of the a typical 10kV system, we verify the feasibility of such selection method. Meanwhile, a hardware design based on the ARM micro processor is conducted for the single phase earthed fault.Fault location has been a hot topic till now. The paper analyzes three existed methods in traveling wave measurement and bring forward wavelet analyzed fault locating theory in locating sinle phase earthed fault point. Combined with A type traveling wave fault location theory, singularity in detecting signals of of wavelet analyzation can help recognize the head wave;Travelling wave are made to reflect and refract between the fault point and the bar when fault occurs.The travel time and speed will determine the fault location.