Objective In metro tunnel sections, evacuation lighting adopts a power supply voltage not exceeding DC 36 V, which leads to challenges such as long power distribution distances, large cable cross-sections, high construction costs, and installation difficulties. Therefore, it is necessary to propose a system using DC 220 V voltage for evacuation lighting in metro tunnel sections, and corresponding anti-electric-shock protection measures.
Method Since the DC 220 V power supply does not fall under safety extra-low voltage (SELV), to address the hazard of electric shock to personnel, the proposed DC power distribution system adopts an IT grounding protection form. In addition, three independent anti-electric-shock measures are proposed: first, insulation monitoring and secondary control are used to cut off faulty circuits; secondly, the PE (protective earthing conductor) line forms a large fault current for tripping to cut off faulty circuits under bipolar insulation faults; thirdly, PE conductor line reduces touch voltage.
Result & Conclusion Analysis and verification show that each independent measure can prevent personnel from electric shock hazards. After implementation, the three measures will effectively prevent electric shock hazards by working together. This provides an effective solution for current metro design and construction, and contributes actively to the high-quality development of rail transit.
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