Research On DC Power Supply System Of Municipal Facilities

There are complex environments,long power supply distances and numerous electrical equipment,large potential safety hazards,and frequent electric shock accidents in municipal power supply scenarios.Existing municipal scenarios use AC systems for power supply,and related studies have shown that direct current causes less harm to humans.Therefore DC power supply system is proposed.At the same time,with the application of LED street lights and the gradual promotion of smart light pole,the DC power supply system is more suitable for powering many of the DC devices,and it is also more conducive to the access of distributed power supplies.This thesis studies the voltage level,grounding method,main wiring type and safety protection of the DC power supply system of municipal facilities.First of all,in order to propose a municipal facility DC power supply system with better safety than the original AC system,it is necessary to determine the safety evaluation index to evaluate the safety performance of the system,which specifically includes setting the risk level based on the effect of human current,fitting the relationship between human resistance and contact voltage according to the standard,and establishing electric shock models of different schemes to determine the expected contact voltage.The safety evaluation index is used to evaluate the safety performance of the AC and DC system,and finally a set of schemes for the DC power supply system of municipal facilities with safety performance superior to AC is obtained.Secondly,the formula derivation and calculation verify that the above scheme can meet the power supply capacity requirements of municipal power supply scenarios.Then,in the set of schemes,the calculation cost of a system scheme that meets the requirements of power supply capacity is selected,which proves that the DC system is not less economical than the AC,economical efficiency is not inferior to AC.Finally,choose different schemes to draw cost curve to optimize power supply radius and line loss to optimize the cost of DC power supply system,and propose a typical DC power supply system.Thirdly,the safety protection scheme is designed on the basis of a typical DC power supply system,mainly for overcurrent protection and electric shock protection.The calculation and analysis proves that the DC system can be protected by DC power supply overcurrent.Then,based on the original AC system,an electric shock protection scheme based on DC RCD was designed for different grounding methods,and the effectiveness of the scheme was proved by fault analysis.The ripple voltage of the power supply system will generate AC residual current through the cable to ground distribution parameters and the equipment to the housing path,which will affect the detection and action of RCD,so path analysis and impedance calculation are performed to lay the foundation for its simulation calculation.Finally,a typical DC power supply system simulation model is established,and the system power supply capacity is verified by the system terminal voltage;the safety protection effect is verified by controlling system failure;according to the above AC residual current theory,the model is created to calculate and analyze the AC residual current,which proves that the system the amplitude of the AC residual current can reach 100 m A,which should be given sufficient attention when designing and developing the RCD of the DC power supply system of municipal facilities.