74 Chapter 6 Maintenance
NetSure 801 CA7 Power Supply System (New Skelecton) User Manual
Table 6-2 Common instruments for power equipments maintenance
Name
Quantity
Applications
Remark
Multimeter
2 to 3 pieces
Measure AC/DC voltage, current and resistance
Those instruments
marked with * may be
configured or not to
those relatively
less-equipped
equipment room
according to actual
requirements
Earth resistance tester
1 piece
Measure the earth resistance
Megommeter (500V and
1000V withstand voltage)
1 piece/each
Dielectric strength test
AC/DC clamp-on amper meter
1 piece
Measure current
Contact Thermometer
1 piece
Measure the temperature of the surface and
junction points of equipment
High/low-frequency noise
tester
1 piece
Measure noise
*Ampere-hour meter
1 piece
Measure battery capacity
AC/DC load meter
1 piece
Measure and test the load capacity of power net,
rectifier and batteries
Note*: testing devices that can be omitted
6.1.3 Reference Technical Specification For Maintenance
The power supply system consists of AC power supply, DC power supply and earthing system. To ensure
communication quality and power supply security, the power supply quality must conform to some basic quality
standards. Reference standards for AC, DC and earth resistance are shown in Table 6-3, Table 6-4 and Table 6-5.
Table 6-3 Quality standards for DC power supply
Standard
voltage (V)
Voltage variation range
at the receiving end of
telecom equipment (V)
Noise voltage (mV)
Maximum permissible
voltage drop of power
supply circuit (V)
Psophometrically
weighted noise
Peak-peak
value noise
Wide frequency noise
(effective value)
-48
-40 to -57
≤ 2mV
≤ 200mV
0 to 20Mhz
≤ 50mV
@3.4kHz to 150kHz
≤ 20mV
@150kHz to 30Mhz
3
24
19.8 to 28.2
≤ 2.4mV
1.8
Note: The voltage drop at the connectors of DC power supply circuit (including the fuse of the feed line output from the
discharging busbar, and battery connectors) shall be in conformity with the following requirements or the temperature rise shall
not exceed the permissible value: 1. If under 1000A, every hundred ampere
≤5mv; 2. If above 1000A, every hundred
ampere
≤3mv.
Table 6-4 Quality standards for AC power supply
Nominal
voltage (V)
Voltage variation
range at the
receiving end (V)
Nominal
frequency
(Hz)
Variation range
of frequency
(Hz)
Power factor
Remark
Below
100kVA
Above
100kVA
The voltage
imbalance of
three-phase power
supply shall not
exceed 4%
220
187 ~ 242
50
± 2.5
≥ 0.85
≥ 0.9
380
323 ~ 418
50
± 2.5
≥ 0.85
≥ 0.9
Table 6-5 Earth resistance reference standards for communication station
Name of the communication station
Earth resistance (Ω)
Comprehensive building, international telecom administration, tandem office, program
control exchange with over 10 thousand lines, and toll exchange with over 2,000 lines.
< 1
Program control exchange with more than 2,000 lines but less than 10 thousand lines, and
toll exchange with less than 2,000 lines.
< 3
Program control exchange with less than 2,000 lines, fiber terminal station, carrier repeater
station, ground satellite station, and microwave junction station
< 5
Microwave relay station, fiber relay station
< 10
Microwave passive relay station
< 20 (may be up to 30
in the
case of high soil resistivity)