Cambium Networks cnWave, Руководство пользователя

Страница: 74 / 248

System Planning 74
l
The PSU shall be connected to ODU drop cable using cable joiner and appropriately rated cables
should be used.
Lightning Surge Protection Units (LPU)
All drop cables connected to the ODU (e.g. PSU and AUX drop cables) requires their own Lighting
Protection Unit (LPU) or Gigabit Surge Suppressor installed close to the ODU and close to the
enclosure/building entry point. The copper SFP drop cable also requires surge protection. Optical cables
do not require lightning surge protection or ground cables. Guidance on the positioning of required
lighting surge protection is given in the
Lightning Surge Protection Units Location .
Drop cable grounding points
To estimate how many grounding kits are required for each drop cable, use the following criteria:
l
The drop cable shield must be grounded near the ODU at the first point of contact between the
drop cable and the mast, tower or building.
l
The drop cable shield must be grounded at the building entry point.
For mast or tower installations, use the following additional criteria:
l
The drop cable shield must be grounded at the bottom of the tower, near the vertical to the
horizontal transition point. This ground cable must be bonded to the tower or TGB, if installed.
l
If the tower is greater than 61 m (200 ft) in height, the drop cable shield must be grounded at the
tower midpoint, and at additional points as necessary to reduce the distance between ground
cables to 61 m (200 ft) or less.
l
In high lightning-prone geographical areas, the drop cable shield must be grounded at the spacing
between 15 to 22 m (50 to 75 ft). This is especially important on towers taller than 45 m (150 ft).
For roof installations, use the following additional criteria:
l
The drop cable shield must be bonded to the building grounding system at its top entry point
(usually on the roof).
l
The drop cable shield must be bonded to the building grounding system at the entry point to the
equipment room.
Lightning Surge Protection Units location
Lightning Surge Protection Units or Gigabit Surge Suppressors must be installed at two points on drop
cables:
l
There is room to mount the LPU, either on the ODU mounting bracket or on the mounting pole
below the ODU.
l
The drop cable length between the ODU and top LPU must not exceed 600 mm.
l
There is access to a metal grounding point to allow the ODU and top LPU to be bonded in the
following ways: top LPU to ODU; ODU to a grounding system.
Find a location for the bottom LPU that meets the following requirements: