地铁低压配电设计问题研究

Research on Design Issues for Low-voltage Distribution in Metro Project

为使地铁工程中的低压配电设计更加合理、安全、可靠,结合一些设计问题案例,采用理论分析和数值计算的方法对低压配电设计问题进行研究。通过对等电位联结设计常见方案存在的问题进行理论分析,得出应按区域设置局部等电位联结板(LEB),不应互联在一起,并且LEB应就地连接结构钢筋;通过对安全特低电压(SELV)照明线路保护管选用金属管时存在的电气安全问题进行分析,得出地铁场所中的SELV照明线路保护管应选用绝缘型管材;通过对配电箱进线开关电器选用隔离开关、断路器2种方案的优缺点进行研究,得出设计人员应重视隔离开关的应用,视具体情况选用开关电器;通过对35 k V系统或0.4 k V系统发生接地故障时以及发生雷击时N导体对地电位情况进行研究,得出选择断路器极数时应考虑使用环境场所;通过对电涌保护器(SPD)应用、区间配电回路接地故障保护问题进行研究,提出合理的技术方案。研究结论对指导低压配电设计工作具有重要意义。

The rationality,safety and feasibility of low-voltage distribution design in metro project are very important.Hence,the low-voltage distribution design is studied by theoretical analysis and numerical calculation based on some design cases.The problems exist in conventional scheme designed by equipotential bonding is theoretically analyzed,and it is concluded that the local equipotential bonding(LEB)should be set according to the region,it should not be connected together,and it should be connected to the structural reinforcement in place.The electrical safety problems when the metal tube is selected for safe extremely-low voltage(SELV)line protection is analyzed,and it is concluded that the insulating type tube should be selected for SELV line protection tube in metro project.The advantages and disadvantages of the two schemes of disconnecting switch and circuit-breaker for the incoming switch in the distribution box are studied,and it is concluded that the disconnecting switch should be paid more attentions to,and the incoming switch type should be rationally selected according to actual conditions.The ground potential of N conductor of 35 kV system or 0.4 kV system in case of ground fault or lightning strike is studied,and it is concluded that the environment should be considered when selecting the pole number of circuit-breaker.The application of surge protector device(SPD)and the grounding fault protection of interval distribution circuit are studied,and a rational technical scheme is put forward.The results is of great significance to the work of low-voltage distribution design.