Chapter 1 Overview 9
NetSure 731 CC2, NetSure 731 C62 Series Power Supply System User Manual
Interface
Functions
Battery 2 fuse
To negative terminal of the battery string 2
DC output positive busbar
To positive terminal of battery string 1 and 2, and load output positive terminal
Priority load MCB
Negative terminal of 48V supply for priority load. Cut off the priority load output w hen the battery
voltage drops to the BLVD point
1.5.5 Earthing Design
Protective earth, SPD earth, and DC operation earth of the power system have been connected to the earth bar
before it is delivered. During the installation, user should connect the grounding terminal to the user earth bar of the
equipment room, as shown in Figure 1-11.
The protective earth cable of 3-phase 5-line system can be directly connected to the earth bar of the equipment room.
The earth resistance should be in accordance with the specifications listed in Table 1-4.
Table 1-4 Earth resistance requirements for communication station
Earth
resistance
Application range
Basis
< 1
Ω
Integrated building, international telecom bureau, tandem station, SPC sw itching
office above 10000 lines, toll office above 2000 lines
YDJ20-88 Provisional
technical regulations of
computerized telephone
sw itching equipment
installation and design
< 3
Ω
SPC sw itching office above 2000 lines and below 10000 lines, toll office below
2000 routes
< 5
Ω
SPC sw itching office w ith less than 2000 lines, optical cable terminal station,
carrier w ave repeating station, earth station, microw ave junction center, mobile
communication machine station
< 10
Ω
Microw ave relay station, optical cable relay station, small-sized earth station
YD2011-93 Microw ave station
lightning protection and
grounding design
specifications
< 20
Ω
Microw ave passive relay station
< 10
Ω
S
uitable for those w hose earth resistance rate is less than 100Ω·m, SPD earth in
the interface betw een electric cable and aerial electric line
GBJ64-83 Industrial and civil
electrical device overvoltage
protection design specification
< 15
Ω
Suitable for those w hose earth resistance rate is 100-
500Ω·m, SPD earth in the
interface betw een electric cable and aerial electric line
< 20
Ω
Suitable for those w hose earth resistance rate is 501-
1000Ω·m, SPD earth in the
interface betw een electric cable and aerial electric line
