Research On Distribution Detworks Fault Location Based Signal Injection

The small current neutral grounding system are adopted mostly in low and medium voltage distribution networks. The advantages of this kind of system are highly reliability and small current when single-Phase-to-earth fault happened. Fault location of single-Phase-to-earth small current neutral grounding system has not been well resolved due to its little current and complicated connection of the branches.Usually we can use traveling wave method, signal injection method and fault indicator technology to locate the fault,but each of these method has it's shortcomings when facing the most difficult problem of distribution network—too many branches, long lines and large grounding resistance,so none of them can solve distribution network fault location problem thoroughly.Aiming at characteristics of low and medium voltage distribution lines and single-phase-to-earth fault, integration location methods of wave-AC and AC-DC for distribution network is put forward based on signal injection. The method and detect of AC signal injection method and detect scheme ,which are to the foundation of accurate location for integration location methods, are put forward. By analyzing the effects of the inductance and distributed capacitance of the line to the AC signal injected to the line,the paper set up the lumped parameter of the line model. Based on the discussions, functions of location reliability with line's distributed capacitance and grounded fault resistor are derived. What's more,two detect schemes are proposed.C-wave method displays the advantages, such as positioning speed quickly and no detecting fault along the lines. C-wave-AC can locate fault point quickly in long line with less branches when fault happens. For DC signal injected method overcomes the influence of distributed capacitance and the resistor,AC and DC are integrated to settle all the faults of the single-phase-to earth, such as large resistor, fault line with long and short branches, and etal.Furthermore, the concept of the resistance and length product is defined ,which is regarded as an elect basis for achieving integrated positioning. The location method proposed is corrected and validated by simulation and field experiments.The design and development of Three kinds of signal sources, pulse signal source, AC signal source and DC signal source,are introduced. Performances of Three kinds of signal sources are analyzed respectively and circuits are designed.Besides,control parts are also described and researched.