With the continuous advancement of the 3G industry, 3G construction is constantly underway. However, the circuit structure of the 3G base station and the 2G base station are different. The 2G base station only has the antenna feed tower, but the 3G base station also has the problem of the RRU (radio frequency remote equipment) on the tower, and the lightning strike environment is relatively bad, which proposes the system lightning protection design. A severe test. Considering the 3G upper tower cable is the optical fiber and the power cable, and generally adopting the fiber without the rib, there is no problem of lightning strike, so the lightning protection of the power source plays an important role in solving the lightning protection of the 3G base station.
Because Power Supply lightning protection is a system engineering, it must be considered as a whole. Generally, it includes the following four aspects: lightning protection of AC power cables, ground connection of base station ground and station equipment, lightning protection of combined power supply system in the station, lightning protection of RRU power line and power port. Only in these four aspects of comprehensive protection can achieve the desired lightning protection effect.
This paper discusses four aspects of lightning protection of 3G base station power supply and provides a complete lightning protection solution for 3G mobile base station power supply.
2 3G mobile base station power supply lightning protection schemeLightning protection for AC power cables
(1) Protection of the AC power cable of the inbound station. For the conditional base station, the high-voltage side cable and the low-voltage side cable of the transformer should be buried. According to the postal code "YD 5098-2005 Communication Bureau (Station) Lightning Protection and Grounding Engineering Design Specification" (hereinafter referred to as 'Postmark') requires that when using a special transformer, the buried length of the high-voltage power cable should not be less than 200M. When the low-voltage cable enters the machine room The buried length should not be less than 15m (when the high-voltage power cable has been laid buried, the low-voltage cable is generally not required), and the low-voltage buried cable should be buried with a metal sheathed power cable or steel pipe. Introduced into the equipment room, the cable metal armor layer should be connected to the transformer ground and the machine room ground at the two ends." However, for high-voltage side cables, buried installation investment and construction are more difficult, and general base stations are difficult to achieve. According to the same standard requirements above, lightning protection lines should be installed along the overhead lines, and high-voltage lightning protection should be installed on the high-voltage side of the transformer. Device.
(2) Install a Class B lightning protection box at the entrance of the AC low voltage power cable into the equipment room. Special attention should be paid to the Class B lightning protection box when installing the "Kevin" wiring to reduce the residual voltage on the lead and give full play to the role of the Class B lightning protection box. For the base station where the AC low-voltage power cable is buried, the attenuation of the lightning current is very obvious after the AC low-voltage power cable is buried, and the B-class lightning protection box can adopt the common varistor lightning protection module with the waveform of 8/20 μs. However, for low-voltage power cables that are not buried, the lightning current may be relatively large. It is recommended to use a high-current-capacity active-ignition type gap-type lightning protection module with a 10/350 μS waveform.
Ground connection between base station ground network and station equipmentThe grounding network of the base station shall be designed in accordance with the seventh chapter of the 'Postmark', "Lightning Protection and Grounding of Small Wireless Base Stations". The grounding resistance shall also meet the standard of less than 10 Ω.
Good ground grid design and low grounding resistance play an important role in the lightning protection of the base station, but this is far from enough. Whether a lightning protection grounding system is successful or not depends on the ground connection (installation) relationship between the devices in the station.
(1) Common unreasonable ground connection of equipment in the station
This is the most common ground connection between equipment in the equipment room. The drawbacks are obvious: the ground lead of the B-level lightning protection box at the entrance of the equipment room is too long to play its due role; the ground wire of the switching power supply is too long, and the residual voltage on the ground line is superimposed on the power supply of the back-end equipment. On the port. For this kind of base station, no matter how good the ground network design is, the grounding resistance is so small that it can not play a good lightning protection effect.
(2) 'Postmark' recommends two equipotential ground connection schemes: ring equipotential bonding and star equipotential bonding.
According to the 'postmark' regulations, when ring-shaped equipotential bonding is used, an annular grounding collection line should be placed along the cable tray and the wall in the equipment room. The ring-shaped grounding collection line should be connected to the ground network at multiple points. The equipment in the station is close to the ring collecting line. Ground."
According to the 'postmark' regulations, when the star equipotential bonding is used, the total grounding busbar of the base station shall be located near the distribution box and the first-stage power SPD, and the grounding busbars of the switching power supply and other equipment shall be connected by the total ground. If the equipment rack is far from the total busbar, a two-stage busbar can be used.
It is recommended to use the equipotential ground connection scheme specified by the 'postmark' for the ground connection of the base station ground station and the station equipment, so that the role of the lightning arresters at all levels can be fully utilized to achieve a good lightning protection effect.
Combined power system lightning protection in the stationFor the lightning protection of the combined power supply system in the station, the lightning protection circuit is relatively simple and mature. According to the 'postmark', the "3+1" with a flow capacity of 40kA (8/20μS waveform) is used on the AC side of the combined power system. The AC C-class lightning arrester of the mode can use the "1+1" DC lightning arrester with a flow capacity of 15kA (8/20μS waveform) on the DC side of the combined power supply.
Speech Translation Mouse,Speech Input Mouse,Voice Search Mouse,Sound Receiver Mouse
Guangzhou Lufeng Electronic Technology Co. , Ltd. , https://www.lufengelectronics.com