Cambium PTP 670 Series, Руководство пользователя

Страница: 152 / 594

Chapter 3: System planning Site planning
Page 3-17
Drop cable grounding points
To estimate how many grounding kits are required for each drop cable, refer to the site
installation diagrams (
Figure 36 , Figure 37 and Figure 38 ) and use the following criteria:
•
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.
•
The drop cable shield must be grounded at the building entry point.
For mast or tower installations ( Figure 36 ), use the following additional criteria:
•
The drop cable shield must be grounded at the bottom of the tower, near the vertical to
horizontal transition point. This ground cable must be bonded to the tower or tower ground
bus bar (TGB), if installed.
•
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.
•
In high lightning-prone geographical areas, the drop cable shield must be grounded at
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 ( Figure 38 ), use the following additional criteria:
•
The drop cable shield must be bonded to the building grounding system at its top entry
point (usually on the roof).
•
The drop cable shield must be bonded to the building grounding system at the entry point
to the equipment room.
LPU location
Find a location for the top LPU that meets the following requirements:
•
There is room to mount the LPU, either on the ODU mounting bracket or on the mounting
pole below the ODU.
• The drop cable length between the ODU and top LPU must not exceed 600 mm.
•
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 grounding system.
Find a location for the bottom LPU that meets the following requirements:
•
The bottom LPU can be connected to the drop cable from the ODU.
• The bottom LPU is within 600 mm (24 in) of the point at which the drop cable enters the
building, enclosure or equipment room within a larger building.
•
The bottom LPU can be bonded to the grounding system.
Multiple LPUs
If two or three drop cables are connected to the ODU, the PSU and Aux drop cables each
require their own top LPU, and the copper SFP drop cable requires a top surge protector, not a
PTP 670 LPU (
Figure 46 ). Optical cables do not require LPUs or ground cables ( Figure 47 ).
The copper SFP drop cable requires a bottom surge protector, not a PTP 670 LPU ( Figure 48 ).
The Aux drop cable may require an LPU near the auxiliary device.