A Novel Method Of Fault Line-Selection Based On The Model Parameter Identification In The Small Current Grounding System

The ground-fault of ungrounded system is used in the distribution net of 6-66kV. It has the virtue of proving power supply’s reliability. But fault selection is not solved when single-phase grounded fault appears, as the small fault current and many reasons. Based on voltage difference of the system the paper puts forward a method of selection line which has higher anti-transition resistance ablility.To address this issue, the paper described the existing theories on fault line selection systematically, and pointed out the defects and drawbacks of those, and summarized the main reason of the fault line selection difficulties in the current. It proposed a new approach to fault line selection based on the model parameter identification method.To a simple isolated neutral system with multiple outlet or arc-suppression-coil-earthed system, when single-phase grounded fault appears we established mathematical model of the zero sequence parameter for every line under non-fault, The model parameter estimation of least square can be solved by the Newton iteration, according to the zero sequence voltage and the zero sequence current. Then compared to the actual difference voltage and the experiential difference voltage to judged the fault line.This paper proposed a new approach to fault line selection, it is very different to the traditional thought. It was proven that the approach had high accuracy, strong resistance for more than to the transition resistance, and had some practical significance to the difficult of the single-phase grounded fault selection in the non-grounded neutral system.