Research On Line Selection Method For Single-Phase Grounding Fault In Complex Distribution Network

The low current grounding mode,adopted in distribution network of our country mostly at present,has the advantanges of reliable power supply.However,the difficulty of fault line selection is increased due to the various fault conditions and unconspicuous fault signal.With the development planning and distributed generation,the structure of distribution network is becoming increasingly diversified and complex,such as hand-in-hand ring and multi-segment multi-contact distribution network.With changing fault characteristics due to different structure,line selection methods,mostly suitable for radial distribution network,will be of great urgency and practical significance to research complex distribution network.Firstly,the development status and significance of low current grounding system are introduced.Steady and transient fault characteristics of traditional radial distribution network are analyzed in non-grounding and resonant grounding system.Draw on the experience of analyzing radiation distribution network,the fault characteristics of complex distribution network,taken hand in hand and loop distribution network as representation,are analyzed about steady and transient characteristics of zero-sequence current to find relationship and difference between fault line and normal line.In addition,the influence of distributed generation,connected with grid by transformer,is analyzed and simulated.Compared the fault characteristics of radiation distribution network,it is found that there are some differences in the complex distribution network.Line selection methods suitable for radiation distribution network will be face with some problems in complex distribution network,which is verified by simulation test results.Secondly,taken the problems of methods mentioned above into consideration,new methods of line selection for complex distribution networks,according to the steady and arc grounding fault characteristics analyzed,is proposed with different neutral grounding modes,including amplitude to phase comparison method and the active component method based on the steady-state component as well as mutual product summation method based on the transient component,of which procedure and flow chart are given and applicable conditions and limitations are pointed out.As a result,a comprehensive analysis method is proposed based on steady and transient state comprehensive analysis.Carried out on the MATLAB/Simulink simulation platform,the simulation results show the effectiveness of the method proposed.Finally,a line selection device,according to the methods proposed,is designed in complex distribution networks with automatic identification of distribution structures.