Main measures of network camera lightning protection
(I) main forms of lightning attacking webcam
The main forms of lightning attack are direct lightning and induction lightning.
1. Thunder is a direct lightning strike on the network camera, causing mechanical damage, which is the most serious damage, but this form rarely occurs in reality
2. induction thunder
Due to the rapid change of lightning current, a strong electromagnetic field is generated around it. The webcam in the magnetic field and its transmission line induce a strong electromotive force, that is, electromagnetic induction; at the same time, the webcam and transmission line in the magnetic field will also induce the opposite charge of lightning, forming electrostatic induction. Induction mine will cause great damage to the monitoring system, which is more common in reality, and is the key protection object.
(II) the network camera is the front-end equipment of the security monitoring system, which belongs to the weak current equipment. Its sensitive components have low tolerance, and are unable to withstand the impact of lightning current. At the same time, this kind of equipment is distributed in the open air, and becomes an important object of lightning attack. In case of lightning stroke, the lightning current will enter the terminal system along the transmission lines such as power supply and signal, while damaging the camera, causing serious damage to the monitoring center. Main measures
(I) lightning protection of front-end acquisition equipment (including network camera)
1. Direct lightning protection measures
When the front-end acquisition equipment (including the network camera) of the monitoring system is within the scope of the direct lightning protection area (lpzoa), the direct lightning protection measures shall be taken, specifically, the lightning rod shall be installed near the network camera, and the protection scope shall be calculated strictly according to the radius of the rolling ball.
When the lightning rod is installed on the installation pole of the camera, the steel pipe of the installation pole can be used as the down lead; when it is installed next to the camera, the distance between the two installation poles shall be more than 3m.
2. The connecting cable of the camera shall be shielded, that is, the connecting cable shall be laid through steel pipe and placed in the steel pipe of the camera mounting rod;
3. The camera metal mounting rod shall be grounded, and the grounding resistance value shall not be greater than 4 Ω.
4. The front end of the network camera shall be equipped with an adaptive surge protector for monitoring signal, which is generally a three in one surge protector ks-e3 / 24 / m for monitoring, network and power supply. The product features are as follows:
Large discharge current, multi-level protection;
Built in fast semiconductor protection device, fast response, low residual voltage;
Excellent core components and performance;
Energy saving, environmental protection, easy installation, suitable for all kinds of standard interface types;
Low insertion loss to ensure smooth line;
The standing wave coefficient is small and the working frequency range is wide.
(II) lightning protection of transmission cable of monitoring system
The transmission cable of the monitoring system shall be protected against lightning wave invasion, and the cable with shielding effect shall be adopted, or the whole process shall be laid with metal pipe through wire. The shielding layer shall be electrically connected, and both ends shall be grounded or connected with equipotential. The part passing through the (lpzoa) area shall be buried. If it is impossible to lay underground, reinforced concrete pole shall be used for overhead laying.
(III) lightning protection for terminal equipment of monitoring system
1. Shielding measures
If the terminal equipment of the monitoring system is non-metallic shell, shielding measures shall be taken, and the distance between the terminal equipment and the structural column of the external wall shall not be less than 1 m.
2. Equipotential bonding
The terminal equipment shall adopt equipotential connection and grounding, and be connected with the lightning protection grounding, protection grounding and other common grounding systems of the building.
Exposed conductive parts of electronic equipment, working grounding of electronic system, etc. shall be connected to the equipotential bonding network through conductor.
3. Reasonable wiring
The integrated wiring of monitoring system shall meet the requirements of technical specifications.
To sum up, the network camera lightning protection is a systematic and comprehensive lightning protection project, which can play a good protective role only if it is carried out in an all-round way