| Recently years,with the significantly increasing investment of construction in China,the development of power distribution network has achieved remarkable results.However,because of the development between urban and rural areas is unbalanced,the energy-use index which includes power and safety in rural areas is lower than that in urban distribution network,especially in the rural areas where the grounding system of low voltage distribution network has low safety issues..At present,the TN-C grounding system of low voltage distribution network is highly recommended by the power supply department due its lower cost.It does not need to install the total leaking protection,thus the cost of wire can be reduced.But the TN-C grounding system must repeat grounding well.Therefore,based on the multi objectives of economic and safety,this paper studies the optimal allocation of TN-C system grounding.This paper reviews the development and research of TN-C system grounding configuration in China and abroad,and discusses the application and research of the optimization algorithm in other aspects of the power grid.It also compares the advantages and disadvantages of particle swarm optimization and several other optimization algorithms,and puts forward the analysis and solution of the particle swarm optimization in TN-C system grounding optimization configuration.The safety issues with all kinds of faults which may appear in TN-C system are analyzed in detail,and it emphasizes the necessity and importance of repeated grounding.At the same time,it points out the safety and economy problems that need to be considered when optimizing the repeated grounding configuration of TN-C system.The constraint optimization theory and multi-objective optimization method are used to optimize the repeated grounding investment and the overvoltage of metal equipment while fault occurring.And the optimization method,optimization principle and particle swarm optimization algorithm are applied to solve this multi-objective optimization problem.The objective function of multi-objective optimization is established by means of linear weighting method.Taking safety voltage as the constraint condition,a mathematical model of grounding optimization for TN-C system is constructed.The symmetric component method is used to decouple the positive,negative and zero sequence networks of the unsymmetrical faults.The fault voltages or fault currents of different types of failures are analyzed and calculated,and then the expression of contact voltage is obtained through series-parallel connection,which constitutes an inequality constraint condition to optimize the grounding configuration of TN-C system.Finally,the particle swarm optimization(PSO)algorithm is applied to solve the multi-objective optimization model of the grounding configuration of the TN-C system.It proposes the basic idea of algorithm and the specific process of solving this multi-objective problem based on MATLAB.According to the simulation analysis of the example,the correctness and feasibility of the optimization algorithm is verified.It provides theoretical and technological support for the reasonable planning and construction of low voltage distribution network TN-C system under the premise of ensuring safety and achieving the lowest construction cost. |
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