The Study Of Single Phase Short-circuit Fault And Protection For10kV Distribution Network With Neutral Grounding Through Low Resistor

Neutral grounding without impedance, neutral grounding through suppressioncoil and neutral grounding through low resistor are the most common neutralgrounding in the10kV distribution network. There are different characteristics andapplication advantages with different neutral grounding. With the development ofdistribution network structure and capacity, low resistance grounding system hasgradually become a better choice. This paper describes the principles of three maingrounding system and their characteristics. focus on the single-phase faultsteady-state and transient short-circuit current of the low resistance grounding system,the distribution of Zero-sequence capacitive current and the distribution of the stepvoltage. It also made a single-phase fault simulation analysis in low resistancegrounding system with different transition resistance. The experiment of single-phasefault in low resistance grounding system is designed and made, and the step voltagedistribution data near the short-circuit fault are gotten. The zero-sequence currentprotection about low resistance grounding system is study.The study of this paper focuses on the following aspects:The development and application trends of neutral grounding in10kV distributenetwork are introduced in this thesis, The overview of the distribution networkshort-circuit fault and protection are also talked in the paper.The steady-state and transient equivalent circuit of low resistance groundingsystem when single-phase ground fault occur are proposed through careful analysis,The steady-state and transient short-circuit ground current are calculated in details.The zero-sequence capacitive current distribution and characteristics are given. Thestep voltage and grounding resistance are elaborated.MATLAB software and its application in power system simulation are described.The simulation model of10kV distribution network with low resistance groundingwhen the single-phase fault occurs is established. The short-circuit ground current,low resistance current, the zero-sequence voltage and three-phase voltage simulationwaveforms are gotten through simulation while the short-circuit transition resistanceare different. The dates are close to the theoretical calculation.Two common short-circuit experimental program are designed and theexperiment procedures and some notes are given in detail. It is demonstrated that the theoretical analysis about the short-circuit current and the step voltage in the paper iscorrect.The zero sequence current protection scheme of the low resistance groundingsystem is study. The detection and acquisition method of zero sequence current, areintroduced. the zero sequence current protection configuration and tuning methods ofthe low resistance grounding system, performance and stability issues are discussed,Finally, the principles and programs of low resistance grounding system are made.