Abstract:

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.

Key words: metro station, lowvoltage distribution, equipotential bonding, circuitbreaker, surge protector device (SPD), earth fault protection