| Neutral grounding is a major technology for the prevention of grid safety accidents,each of which has its own applicable conditions.China’s distribution network mainly uses small current grounding way.But with the rapid development of the city,small current grounding way exposed a variety of problems.Therefore,this paper proposes changing the neutral grounding method into a small resistance grounding way,and carries out both technical and economy feasibility assessment of the transformation program.This paper introduces the use situation of the neutral grounding method in the distribution network at home and abroad.And analyzes the principle of non-grounded,the arc-suppression coil grounding and small resistance grounding.At the same time,the electrical characteristics of single-phase grounding fault are briefly introduced.In the transformation program,this paper works from the determination of the best neutral grounding resistance and the relay protection adjustment.First of all,limiting the range of the neutral grounding resistance according to the system technical requirements and safety considerations.And then establishing the relationship between the equipment cost and the neutral grounding resistance,and determine the resistance with the best economy.Making adjustment suggestions on the protection of major equipment according to the characteristics of single-phase grounding fault.At the same time,this paper assesses the transformation program at both technical and economy aspects.First establishing the fault trip rate model under different neutral grounding methods,which contains the type of line.Then,in order to achieve the purpose of the technical assessment,this paper quantitatively calculates the power supply reliability index,which considering the grid structure and automation level of the distribution network.Finally,this paper establishes a whole life cycle cost model to achieve the purpose of economy assessment of the transformation program. |
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