The grounding extraction device in the subway grounding system must be connected to the grounding grid through grounding extraction lines when connected to electrical equipment to meet the protection requirements for fault currents. Previous practices involved directly extracting grounding extraction lines from the structural base or through PVC pipes. This method often fails to meet the protection requirements for fault currents, as groundwater can easily seep out from the grounding extraction lines, not fulfilling the design specifications or providing adequate protection. The grounding extraction device is specifically designed and produced to address this issue. It can be widely used in grounding extraction devices for subway systems, electrical equipment, and integrated grounding grids, effectively preventing groundwater overflow and providing excellent protection against stray currents.

Installation precautions for grounding lead-out devices:

1. The outer surface of the grounding lead-out device protective tube is coated with anti-rust paint (epoxy coal tar thick paint).

2. The grounding lead-out device's protective tube extends 100mm above the ground-level building structure. The reserved length of the grounding lead-out wire is at least 400mm above the opening of the protective tube.

3. The grounding lead-out device protection tube passes through the center of the steel reinforcement mesh on the structural bottom plate (without contacting the structural reinforcement), and the space between the grounding lead-out wire and the protection tube is filled with insulating filling material; insulation between the grounding lead-out wire and the structural reinforcement.

4. The location of the grounding lead outlet point should be near the cable well under the platform slab or in the cable channel beneath the strong/weak electrical equipment room on the platform level, avoiding the undertrack air duct, structural walls, and tracks, etc. The position of the outlet point must be confirmed by relevant authorities.

5. Strengthen the protection of the grounding lead-out device during construction to prevent mechanical damage and chemical corrosion.

6. The connection between the grounding lead-out wire and the grounding grid is done using thermal fusing (hot welding) method.