How do video surveillance surge protectors protect the device?

In order to adopt effective lightning protection measures for the video surveillance system, the composition of the video surveillance system and the causes of lightning damage should be accurately understood first.

Thunderstorm season video surveillance surge arrester facilities

I. What are the reasons for damage caused by lightning to the video surveillance system?

(1) The composition of the video surveillance system generally consists of the following three parts:

I. Front-end part: It is mainly composed of a camera, a lens, a head, a protective cover, a stand, and a decoder.

II. Transmission part; use cables, wires to take overhead, buried or laid along the wall and other methods to transmit video, audio or control signals.

III. Terminal Part: Mainly consists of picture splitter, monitor, control equipment, video storage device and so on.

(2) The main reason for damage caused by lightning to the video surveillance system

I. Direct lightning: lightning strikes directly on the open camera, causing equipment damage or lightning strike directly on the overhead cable and causing damage to the cable. This lightning strike caused the most serious damage, but the probability of occurrence was relatively small.

II. Inductive lightning: also known as secondary lightning, it is divided into electromagnetic induction and electrostatic induction. When lightning strikes and flickers in nearby areas, a strong transient electromagnetic field will be generated around the strike channel. The monitoring equipment and transmission lines in the electromagnetic field will induce a large electromotive force. This phenomenon is called electromagnetic induction; when a charged lightning cloud appears, it will induce thunderclouds on the buildings and transmission lines under the thundercloud. The opposite charge, this phenomenon is called electrostatic induction. The equipment damage caused by induced lightning is not damaged by direct lightning, but the probability of occurrence is very high, accounting for more than 80% of modern lightning accidents.

III. Lightning Invasion Waves: When a power cable, signal transmission line of a monitoring system or other metal cable entering a monitoring room is struck by a lightning or is induced by lightning, a lightning wave intrudes into the device along these metal wires/conductors, causing a high potential difference to damage the device.

Second, video surveillance system lightning protection measures?

(1) Lightning protection of front-end equipment: The front-end equipment has two distribution modes, outdoor and indoor, and the indoor distribution will not be subject to direct lightning strikes. However, it is necessary to consider the protection against lightning over-voltage against the equipment, while the outdoor equipment needs to be protected at the same time. Consider preventing direct lightning strikes.

Front-end equipment such as cameras should be placed within the effective protection range of the lightning rod. For front-end equipment that is already within the protection scope of other lightning rods or high-rise buildings' original lightning protection system, it is generally no longer necessary to consider direct lightning protection; for front-end equipment that is not within the protection scope of any lightning protection system, it should be considered Lightning protection problem.

(2) Lightning protection of transmission lines: More than half of the monitoring system's lightning accidents are caused by lightning intruding wave overvoltages induced on the lines connected to the system. Therefore, doing well the line protection connected to the system is a part of the overall lightning protection that cannot be ignored. The video surveillance system is mainly transmission signal lines and power lines.

The safe wiring method shall be laid through the whole process of wearing the metal pipe. At the same time, it must be noted that the two ends of the metal pipe must be effectively grounded. The power supply of the camera generally uses AC220V or DC12V. The camera is powered by a DC transformer. The single-phase power surge protector should be connected in series or parallel to the front of the DC transformer. If the transmission distance of the DC power source is greater than 15 meters, the camera should be connected in series with a low-voltage DC lightning arrester.

(3) Lightning protection of terminal equipment: The lightning protection of the monitoring room is the core of the lightning protection system. It should be conducted in various ways from direct lightning strike protection, lightning intruding wave, equipotential bonding and surge protection.

The main equipment of the monitoring room includes the monitoring center computer, video matrix, hard disk recorder, intercom system, and power supply of the monitoring room. The location of the equipment room of the monitoring system equipment should be selected in the LPZ advanced area and avoided in the top three floors of the building; when the size of the lightning protection grid on the building surface part does not meet the requirements of the system anti-jamming, the shielding should be installed on the sky surface. Floor. Use unshielded cables. Before entering the home, wear a metal tube and bury it in the ground at a horizontal distance of 10 meters or more. If it is impossible to wear a metal pipe buried in a house due to conditions, the length of the access shield pipe or the trestle shall be extended. Equipotential bonding and grounding shall be performed at both ends of the metal pipe or trestle bridge and at the junction of the lightning protection zone. When the monitoring system equipment is a metal enclosure, short conductors are used to connect it to the equipotential bonding strip. If it is a non-metallic shell, when the shielding of the building where the equipment is located does not meet the equipment's electromagnetic compatibility requirements, metal screens or other shields shall be installed to shield the equipment. The metal mesh shall be connected to the equipotential bonding tape for equipotential bonding. Computers, telecommunications, and monitoring equipment should be protected by a distance of about 1 meter from the building's external walls. In order to prevent the building from being hit by direct lightning, strong electromagnetic fields are generated around the down conductors that leak into the ground along the outer wall and damage the microelectronic equipment.

I. Lightning protection measures for the power system of the monitoring room

Because 70% of the lightning high voltage is invaded from the power line, in order to ensure the safety of the equipment, three levels of lightning protection should be set on the general power supply.

a. A three-phase surge protector is installed at the main power distribution section of the building in which the monitoring room is located. The flow capacity is 80 kA (waveform 8/20 μs) and is used as the primary protection of the power supply.

b. Install a three-phase modular power surge protector at the power distribution box in the monitoring room. The maximum flow capacity is 40 kA and it is used as the second level of protection.

c. Install a single-phase series arrester in front of the monitoring room UPS power supply or monitoring equipment and install them in series to protect the power line at the third level.

d. A single-phase lightning protection socket with a flow capacity of 10 kA is installed in front of the equipment in the monitoring room to provide lightning protection for the fine power supply and to clamp and filter the power supply.

If it is not possible to classify the power surge protector, it is recommended to install the BC composite three-phase power source lightning arrester in the monitoring room. A single-phase series power surge arrester is installed before the UPS power supply in the monitoring room as the third-level protection of the power line. The flow-through capacity of the 10KA single-phase power supply lightning protection socket is installed in front of the monitoring room equipment. As a fine power lightning protection, power clamp and filter.

II. Lightning Protection Measures for Control Room Control and Intercom System

a. The control room video uses a 16-port modular video lightning arrester to protect the video input port of the hard disk recorder from being damaged by surge voltage. Camera guns that transmit signals from optical fibers do not consider installing video surveillance surge protectors.

b. The RS232 interface of the hard disk recorder uses the RS232 interface arrester to protect the serial port of the hard disk recorder from being destroyed by the surge voltage.

c. All control lines entering the control room are equipped with control line lightning arresters.

d. Install the audio line lightning arrester in the wired intercom system, install the lightning arrester only on the end of the intercom host.

The above are just some basic lightning protection measures. The real video monitoring system needs lightning protection to be comprehensively considered in all aspects, and the lightning protection technology is also very complicated. The performance requirements for various monitoring and arrester devices are also relatively high, but everyone can Taking the above lightning protection as a basis, and deepening in all aspects, the monitoring system can be protected from lightning strikes to the maximum extent and effectively achieve the purpose of lightning protection and disaster reduction.