Research Of New Technology On Singie-Phase-to-Earth Fault Location In Distribution Network

Most of the distribution network in china is the small current grounded system, in which the single-phase-to-earth fault location has not been solved for a long time. According to the idea of locating the fault section firstly and the fault point secondly, this paper analyses the zero sequence network characteristics after the single-phase-to-earth fault happens in different distribution network, obtains fault segment positioning principle in ungrounded system and resonant grounding system and designs distribution network single-phase-to-ground fault segment location system based on above-mentioned principle.For the single-phase grounded fault in the ungrounded neutral system, zero-sequence current phase criterion and amplitude criterion can be got by amplitude and phase characteristics of zero-sequence current. In the resonant grounded system, the compensation of the arc suppression coils makes the amplitude of fault current decrease and its polarity changed, so that single-phase-to-earth fault location gets more difficult. Live location method is proposed for single-phase-to-earth fault section in neutral point resonant grounded system. By this method, the compensation current of arc-suppression coil is adjusted after the fault occurs and the fault section can be confirmed by variation of zero-sequence current in the line. The method is proposed that the zero-sequence current is converted by zero-sequence voltage when single-phase-to-earth via resistance occurs, which settles the problem that zero-sequence voltage changes after the arc-suppression coil is adjusted.The distribution network single-phase-to-ground fault segment location system based on above-mentioned principle mainly includes two parts, the system master station and detection terminals. The system master station can realize receiving remote data, issuing control command, processing data and judging fault. The detection terminals which include current detection terminal and voltage detection terminal, mainly realize the data acquisition of zero-sequence voltage and zero-sequence current, wireless transmission of related information. GPS technology is taken to ensure the sample synchronicities of voltage and current, and GPRS technology is taken to realize the related data information wireless transmission of zero-sequence voltage and zero-sequence current.In the wake of the fault segment location, the fault point location is made by the "S" signal injecting method. The paper analyzes the influence of capacitance and grounding resistance on "S" signal injecting method and concludes the prerequisite to correct location. A method is proposed to improve the accuracy, by which the vector relationship of "S" signal voltage and current vector is tested to locate the fault point. The voltage vector is tested in the transformer substation, while the current vector is tested on the line. So it puts forward to a technique scheme based on GPRS mobile communication technology and synchronized vector measurement, and introduces the structure of fault location device. The site experiment results show the correctness and applicability of this method.Furthennore,The fault loeation device we design has been put into use in the field and running well. Also its reliability and feasibility have been fully verified.