Requirements for Lightning Proof Grounding

Table 1 lists the requirements for lightning proof grounding.

Table 1 Requirements for lightning proof grounding



Capital construction

  • Use reinforced concrete to construct the equipment room.
  • Install a lightning proof device like a lightning rod outside the room.
  • The lightning proof ground shares the same grounding body with the protective ground of the room.

Power cables leading in the equipment room need to be equipped with a surge protector

  • After the AC low-voltage power cables are led into the room, install the surge protector for the power cables in the AC voltage stabilizer and the AC power distribution panel (box). Correctly ground the surge protector nearby.
  • After the DC power cable is led into the equipment room or outdoor cabinet from outdoors or outside the cabinet, install a power lightning protection device for the DC power cable. The lightning protection device should be grounded in proximity.
  • For an equipment room in urban area, install a power supply surge protector with the nominal discharge current of no less than 20 kA. For an equipment room that is built in a suburb and subject to lightning strikes, install a power supply surge protector with the nominal discharge current of more than 60 kA. For an equipment room that is built in a mountain area and subject to frequent lightning strikes, or in a separate high-rise building in a city, install a power supply surge protector with the nominal discharge current of more than 100 kA.
  • The ground cable of the surge protector should be no longer than 1 m (3.28 ft).

Grounding for DC power distribution

  • Connect the DC working ground (positive pole of the -48 V DC power supply or the negative pole of the 24 V DC power supply) with the indoor collective ground cable nearby. The total ground cable should meet the maximum load of the equipment.
  • The power equipment must have a DC working ground cable, which can connect the power equipment to the collective ground cable of the telecommunication site (or the protective ground bar of the equipment room).

Equipotential connection

  • Properly ground the devices and auxiliary devices in the room such as mobile base station, transmission, switching equipment, power supply equipment, and cable distribution frame. Connect all PGND cables to the collective protective ground bar. Connect all PGND cables in one equipment room to one protective ground bar.
  • Apply joint grounding to the working ground and protective ground of devices, which means the two share one grounding network.
  • The cable tray, rack or shell, metal ventilation pipe, metal door or window of the equipment should be grounded for protection.

General requirements for grounding

  • Do not connect the neutral line of the AC power cable with the protective ground of any telecom equipment in the equipment room.
  • Do not install a fuse or switch on the ground cable.
  • All ground cables should be as short as possible, and arranged in a straight line.

Grounding resistance

  • The grounding resistance must be lower than 1 ohm.
  • The upper end of the grounding body should be at least 0.7 m (2.30 ft) over the ground. In cold areas, bury the grounding body below the frozen ground.
  • Measure the grounding resistance periodically to ensure effective grounding.

Routing of signal cable

  • Do not arrange the signal cables overhead in the equipment room. All signal cables must be led into the site underground.
  • Use the cables with a metal jacket or place them into a metal pipe if they come out/in the equipment room.
  • Ground the idle lines inside the cable in the equipment room.
  • Signal cables should be deployed on internal walls. Do not deploy outdoor aerial cables.
  • Keep signal cables away from power cables and surge protection devices.

Collective ground cable

  • Use a ground ring or ground bar for the collective ground cable.
  • Do not use aluminum cables as ground cables. Adopt measures to prevent electrification corrosion when connecting different metal parts together.
  • Use a copper busbar as the collective ground cable with a cross-sectional area of no less than 120 mm2 (0.19 in.2), or use the galvanized flat steel of the same resistance. Insulate the collective ground cable from the reinforcing steel bars of the building.

Grounding lead-in

The grounding lead-in should be a maximum of 30 m (98.42 ft) long. Use the galvanized flat steel with cross-sectional area of 40 mm x 4 mm (1.58 in. x 0.158 in.) or 50 mm x 5 mm (1.97 in. x 0.197 in.).

Copyright © Huawei Technologies Co., Ltd.
Copyright © Huawei Technologies Co., Ltd.
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