1. Harm of
lightning strikes Lightning strikes are one of the serious natural disasters. With the continuous development of modern communication technology, increasingly busy and complex affairs can be organized in order through computers, networks and communication equipment, but the working voltage of these sensitive electronic equipment is constantly changing. Decrease, their number and scale continue to expand, so the possibility of them being damaged by overvoltage, especially thunder and lightning, is greatly increased. The consequences are not only direct damage to the equipment, but also may interrupt the operation of the entire system and cause difficulties. Estimated economic loss. Therefore, lightning protection of equipment has become an urgent need.
Second, the classification lightning
lightning is generally divided into direct lightning and lightning.
Direct lightning refers to: lightning strikes directly on buildings, structures, trees, animals and plants, and directly destroys buildings and structures and causes casualties due to electric and thermal effects.
Inductive lightning refers to the discharge between thunderclouds or between thunderclouds and the ground, which generates induced voltage on nearby overhead lines, buried lines, metal pipelines or similar conductors, and this voltage is transmitted to the equipment through the conductors, resulting in a network Large area damage to system equipment.
Third, the intrusion passage of lightning
lightning invasion network equipment, mainly in the following four ways:
(1) direct lightning stroke by lightning receptor is directly into the ground, resulting in the net lift near ground, caused by the introduction of high voltage equipment grounding conductor Potential counterattack.
(2) When the lightning current enters the ground through the down conductor, the high current rate of change generates a strong magnetic field around the down conductor, causing the surrounding equipment to induce overvoltage.
(3) The power line or video line, RS485 pan/tilt control line that enters and exits the monitoring center is directly struck by lightning or induced lightning outside the building, and overvoltage and overcurrent enter along the line to invade the equipment.
(4) Into the power supply, pan-tilt control, and video lines of the outdoor camera, the induced lightning current intrudes into the camera and damages the camera.
Fourth, the comprehensive lightning protection system
With the continuous development of modern electronic technology, the power lines, signal lines, and antenna feeders of communication equipment are easily damaged by lightning strikes. In general, lightning strike protection is divided into external protection and internal protection, which are also called lightning strikes. The classification of protection.
(1) External protection: It is composed of air-termination device, down conductor and grounding device, mainly used for the protection installation of direct lightning strike.
(2) Internal protection: It is composed of equipotential bonding system, shared grounding system, shielding system, integrated wiring and SPD, mainly used for lightning electromagnetic pulse protection.
5. Direct lightning protection
(1) A lightning rod should be installed above the pole of the outdoor camera, and the camera should be within the protection range of the lightning rod.
(2) The camera installed with the help of buildings should be within the protection range of the building lightning rod or other lightning protection device. If the building lightning protection device cannot be used for protection, the lightning rod should be installed on the monitoring pole as an air-termination device, and the air-termination device should be nearby. Grounded by the lightning protection belt and lightning protection net of the building.
(3) Small lightning rods should be round steel or steel pipes. When round steel is used, the diameter should not be less than 16mm; when steel pipes are used, the diameter should not be less than 25mm, and the thickness of the steel pipe wall should not be less than 2.5mm. The tip of the lightning rod should be 1m higher than the top of the antenna.
(4) grounded lightning down conductor should be galvanized or round cross-sectional area of not less than 8mm in diameter is not less than 48mm² of
six, lightning protection
outdoor camera is LPZ1 area, vulnerable to an overcurrent induced by power supply cable Intrusion into the camera, the focus of protection is the power supply, while the camera’s power supply, network and other lines must be considered comprehensively.
1. Outdoor monitoring power supply system protection
(1) Outdoor monitoring power supply system general protection:
Outdoor cameras and fiber optic transceivers use many integrated circuits and sophisticated components. The breakdown voltage of these devices is often only tens of volts, and the maximum allowable operating power is only mA level. If the third level of lightning protection is not implemented, the breakdown voltage of these devices is only tens of volts. After the power line surge reaches thousands of volts, this will cause a great impact on the outdoor surveillance camera and cause damage to the camera.
Install Opelei Class I lightning protection device PB15-385/B+C/2, 15kA (10/350μs) here, which can effectively limit the residual voltage to within kV. This level of lightning protection device is installed in parallel, and the rear The power of the connected equipment is not limited.
(2) Outdoor monitoring power supply system power terminal protection:
Install Ou Pele II power lightning protection device PD20-275/2, 10kA (8/20μs) in the outdoor monitoring box, as the power terminal protection of the monitoring power supply system.
2, outdoor camera comprehensive protection
currently using network cameras mainstream high-definition cameras, here you need to install the power control network EU spectrum Ray triple mine SN-3/24.