Radio community antenna television system and cable television system of lightning and the lightning protection of microwave system has many similarities, such as days of feeder line lightning protection, signal transmission cable lightning protection requirements are basically consistent. Just signal cable television system to the alleys from families, some of its body, the details shall be explained. At present the wireless television USES the common receiving device to occupy the majority, therefore it actually and the cable television system in the lightning protection technology is consistent.
Except the antenna and the part directly connected with the antenna will be destroyed by direct lightning, other lightning hazards mainly come from the transmission line and the lightning wave of the power line. In terms of the form of lightning invasion, the ground potential is mainly increased by direct lightning strike. Therefore, doing a good job in lightning protection of equipment and correctly selecting and installing lightning protection devices are the key measures to do a good job in lightning protection of TV system.
1. Lightning protection measures for radio towers and equipment
Used in radio, television and communication equipment. Its transmitting and receiving antennas are often put on a tall tower, they are more exposed to the lightning space. So the antenna are often a target of a lightning strike. But most of the metal antenna has the protection performance, even if the microwave parabolic antenna, horn antenna, satellite ground stations. As long as its grounding metal stents have good electrical connection is not bad been hit by lighting. For example, folding type symmetrical oscillator, it is necessary to provide a short circuit for lightning protection of antenna oscillator and coaxial cable from the structure, so that the lightning current can be directly transmitted to the ground for safety.
As mentioned earlier, most microwave towers are steel in themselves and do not require special protection other than proper grounding at the bottom. However, all waveguide, coaxial, and other cable metal sheaths must ensure a good electrical connection between the tower top and the tower body, and repeated electrical connections must be made every 30 m or so to ensure voltage equalization. The broadcast tower usually USES the cable, should pay attention to causes the cable fixed point not to be damaged, and its outer skin metal and the steel bar welding.
The radio equipment in the tower must do equipotential connection with many points of the tower, which is the necessary guarantee of personal and equipment safety.
A good grounding structure of zui radio station is a closed balanced grounding device embedded around the foundation of a building or tower, because such a grounding device not only makes the connection between points convenient, but also can achieve potential balance in the closed loop.
Radio towers are often built on hilltops, where the foundation is often rock, and low grounding resistance is costly and difficult to achieve. In this case, it is more important to ensure that all power cables, metal sheaths, waveguides entering the building, tower legs, neutral wires of power transformers, and all external metal pipes, etc. are well equipotential connected than to make certain that the grounding limits are very low. In this case, it should be noted that when lightning strikes the tower, the potential of the tower itself will increase, which may lead to a very high step voltage and contact voltage. Therefore, corresponding measures should be taken to prevent contact voltage and step voltage. Equipotential connection is a good way to prevent stepping voltage and contact voltage zui.
3. Lightning protection of signal feeder
1. Coaxial cables down the vertical pole (frame) of the antenna shall be led by double shielded cables or single shielded cables through the metal pipe. The outer shielding metal film of the double shielded cables or the ends of the metal pipe shall be well connected with the vertical pole and the ground network. And between the cable core and the shielding layer should be equipped with the appropriate shenzhen lightning arrester.
Set up near the antenna of the antenna amplifier, if using a separate power supply, power supply cord shall be separate wear metal pipe laying, metal tube must be reliable grounding on both ends of the fore and aft, the feeder line lightning protection device must be mounted to the harpies sometimes. The power cord of the zero line should be with the coaxial cable of the metal shielding layer or threading tube to do a good electrical connection. Signal system and power system in order to achieve zero potential. It is strictly prohibited to use ordinary wire overhead Ming fu.
2. Both ends of the overhead cable suspension line and metal pipes in the overhead cable line shall be connected to the ground. Overhead cable lines in the suburbs shall be grounded at branch poles, lead poles, terminal poles, poles for installing antenna amplifiers, and every 5-10 poles for linear lines. The signal source and power supply at the input end of each intermediate amplifier shall be connected to the appropriate lightning arrester. The grounding end of the lightning protection shall be grounded at the same point as the cable shielding layer.
3. Outdoor power lines that supply power to system equipment or user equipment from outside.
4. When buried cables enter the building, the outer metal shielding layer of cables shall be grounded close to the place where cables enter the building.
5. When the overhead cable is directly introduced and the overhead metal pipe enters the user, it shall be electrically connected with the grounding device.
6. Electrical equipment grounding devices and buried metal pipes in the system shall be electrically connected with lightning protection grounding devices. If not connected, they shall be separated by no less than 3 m.
7. Cables shall not be laid directly between the roofs of two buildings to prevent direct lightning strikes. Cables shall be lowered along the walls to the protection area against direct lightning strikes and shall not hinder the operation of vehicles. Its suspension wire (metal wire) should make good ground.
8. All TV receivers shall be installed with shenzhen thunder son TV signal lightning protection device and special power supply lightning protection module for electronic equipment power supply. Transmission of lightning current from signal transmission lines and electric W lines.
9. The camera shall be supplied by the special lead line of the monitoring room through the isolation transformer. The remote camera can be powered nearby, but the equipment should have a switch, fuse and voltage stabilizer in addition to the lightning protection device.