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R250D-E
Hardware Installation and Maintenance Guide
Item
Power cables
leading in the
equipment room
need to be
equipped with a
surge protector
Grounding for
DC power
distribution
Equipotential
connection
General
requirements for
grounding
Grounding
resistance
Issue 01 (2016-09-30)
Requirements
l After the 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.
l 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.
l The ground cable of the surge protector should be no longer than 1
m (3.28 ft).
l 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.
l 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).
l 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.
l Apply joint grounding to the working ground and protective ground
of devices, which means the two share one grounding network.
l The cable tray, rack or shell, metal ventilation pipe, metal door or
window of the equipment should be grounded for protection.
l Do not connect the neutral line of the AC power cable with the
protective ground of any telecom equipment in the equipment room.
l Do not install a fuse or switch on the ground cable.
l All ground cables should be as short as possible, and arranged in a
straight line.
l The grounding resistance must be lower than 1 ohm.
l 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.
l Measure the grounding resistance periodically to ensure effective
grounding.
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
5 Appendix
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