The Research Of Optimization Of The Netrul Grounding Mode Of 10kV Power Grid In Yangjiang

The 10 kV power grid in Yangjiang area has three grounding modes: ungrounded neutral point,grounded neutral point through arc suppression coil and grounded neutral point through small resistance.With the economic development of Yangjiang area,the scale of distribution network in Yangjiang area is expanding,the cabling rate of 10 kV power grid lines is also increasing,and the system capacitance current is growing rapidly;The important load of10 kV power grid is increasing day by day,and the requirements for power supply reliability are also increasing;Considering the above factors comprehensively,the original neutral point grounding mode of 10 kV power grid may not match the current operation demand and needs to be optimized.In addition,as an energy base,the photovoltaic power supply is gradually connected from the 10 kV grid grid,which will also cause changes in the fault characteristic current of the 10 kV grid.How to make better decisions on the grounding mode of the branch transformer of the distributed power supply remains to be studied.The main work of this paper includes:(1)This paper analyzes the operation characteristics of three neutral point grounding modes of 10 kV power network,namely,ungrounded,arc suppression coil grounded and small resistance grounded,and their application in Yangjiang area;(2)The optimization of neutral point grounding mode is studied,focusing on the optimization of neutral point resistance value of small resistance grounding mode.The objective function is obtained by weighted summation of three evaluation indexes of line selection accuracy,single-phase grounding fault current and non fault phase overvoltage multiple on the membership degree of the optimal value interval.The relationship between neutral point grounding resistance value r and the objective function is established through fuzzy membership function,Then the particle swarm optimization algorithm is used to solve the maximum of the objective function and the corresponding neutral resistance r.(3)The single-phase grounding fault characteristics of 10 kV power grid after the inverter type distributed power supply is connected to the grid are studied.The influence of different grounding modes combination of 10 kV power grid neutral point and distributed power grid connected transformer neutral point on 10 kV power grid fault current and zero sequence current is analyzed.Finally,the decision-making principle of neutral point grounding mode of distributed power grid connected transformer is given based on the simulation calculation to verify the theoretical analysis results.Through the research in this paper,the effectiveness of particle swarm optimization method for the neutral point grounding mode of 10 kV power grid is verified.In addition,the principles that should be followed for the optimization of the neutral point grounding mode of grid connected transformers of distributed generation are also proposed,which has a good guiding significance for the optimization and reconstruction of the neutral point grounding mode of 10 kV power grid in Yangjiang area.