Chapter 2 Installation Preparation 21
NetSure 801 CA7 Power Supply System (New Skelecton) User Manual
should be no less than 25mm
2
, the cable should be as short as possible, and so is the earth cable of the Class-B
SPD. The SPDs should be inspected periodically to ensure their normal operation.
48VDC
+
-
A
B
C
N
PE
5~10m
Class-B SPD
SPD
DC earth
Protective earth cable
User earth bar
System earth bar
Protective earth
Power
supply
system
SPD earth
SPD earth
DC earth cable
Figure 2-3 Diagram of SPD mounting & system earthing
Earthing requirement
The earthing system in the communication equipment room is generally designed on the principle of common earth,
that is, DC operation earth, SPD earth and protective earth sharing the same earth. The earth resistance should be in
accordance with the specifications listed in Table 2-2.
Table 2-2 Earth resistance requirements for communication station
Earth resistance
Application range
<1Ω
Integrated building, international telecom bureau, tandem station, SPC switching office above 10000 lines,
toll office above 2000 lines
<3Ω
SPC switching office above 2000 lines and below 10000 lines, toll office below 2000 routes
<5Ω
SPC switching office with less than 2000 lines, optical cable terminal station, carrier wave repeating station,
earth station, microwave junction center, mobile communication machine station
10Ω
Microwave relay station, optical cable relay station, small-sized earth station
<20Ω
Microwave passive relay station
<10Ω
Suitable for those whose earth resistance rate is less than 100Ω·m, SPD earth in the interface between
electric cable and aerial electric line
<15Ω
Suitable for those whose earth resistance rate is 100-
500Ω·m, SPD earth in the interface between electric
cable and aerial electric line
<20Ω
Suitable for those whose earth resistance rate is 501-
1000Ω·m, SPD earth in the interface between electric
cable and aerial electric line
Note: the content in the table is adapted from Installation Design Specifications for Communication Power Supply Equipment
2.1.5 Equipment Running Environment Checklist
The equipment running environment checklist is given in Table 2-3.
Table 2-3 Equipment running environment checklist
No.
Item
Index
Pass
1
Ambient temperature in equipment room
-5°C to +40°C
Yes/No
2
Humidity in equipment room
≤ 95%
Yes/No
3
Lighting in equipment room
70 ~ 200Lux
Yes/No
4
Height of equipment room
≥ 3m
Yes/No
5
Static electricity in equipment room
Lay antistatic floor or antistatic rubber
Yes/No
6
Weight capacity and quakeproof ability
Accord with Level 8 quakeproof, and safety must be ensured
Yes/No
7
Radiation
No blockage in equipment radiation passage
Yes/No