How to deal with outdoor lightning protection in summer thunderstorms?

First, the principle of lightning protection

1. Direct lightning strikes directly into the ground through the lightning receptor [such as lightning rod (belt)], down conductor and grounding device, causing the ground potential to rise. The high voltage is introduced into the electronic device by the device ground wire to cause the ground potential to counterattack.

2. When the lightning current enters the ground along the down conductor, a magnetic field is generated around the down conductor, and various metal tubes (lines) around the down conductor are induced to generate an overvoltage.

3. The power and signal lines entering and exiting the building or computer room are infiltrated into the electronic equipment by lightning voltage and overcurrent that are loaded by direct lightning or inductive lightning outside the building. Therefore, we protect the lightning surge and overcurrent of the entire intrusion in the above three ways.

The complete system lightning protection scheme includes two aspects: external lightning protection and internal lightning protection:

1. External lightning protection includes lightning receptors (lightning rods, belts, wires), down conductors (building reinforcements, manual down conductors), grounding devices (grounding bodies, grounding networks), etc. Their main function is to ensure The building body is protected from the direct lightning strike, and the lightning that may hit the building is discharged into the earth through the lightning rod, the lightning protection belt, the down conductor, the grounding body, and the like.

2. The internal lightning protection system is set to protect the equipment inside the building and the safety of personnel. Install a suitable lightning arrester at the front end of the equipment to be protected so that the equipment, the line and the earth form a conditional equipotential body. The lightning current that may enter is blocked, and the lightning current induced by the internal facilities can be safely discharged into the ground due to lightning strikes to ensure the safety of the connected equipment.

When the lightning occurs in a place close to the building, the lightning induced electric shock that may hit the building body through the lightning rod is sucked into the earth through the lightning rod, and the induced electromotive force generated will cause damage to all the internal metal lines. The induced current is due to the inductive lightning current on the power, network, communication and other lines, which increases the possibility of damage to the sensitive computer and other equipment inside the building. The installation of the lightning rod does not provide a complete internal protection and lightning protection measures. , will greatly increase the chance of lightning damage accidents, at this time the lightning rod has really become a lightning rod.

When a thunderstorm cloud appears near the building where it is located, lightning will not generate lightning currents in the power supply and network system of the internal equipment of the building when the lightning current is not discharged through the lightning protection belt at the top of the building, resulting in damage to the equipment. Therefore, the computer system connected through the power supply, network and communication line inside the building is expected to pass the more traditional method: it is impossible to install the lightning rod to avoid the accident of lightning strike. As the lightning protection of the internal system, only the external protection such as the lightning rod is used. Lei, its role is not sufficient. Only for the characteristics of inductive lightning damage to the equipment, the solution to prevent inductive lightning strikes can be used to avoid lightning strikes on the equipment.

Since there are many ways to generate inductive lightning, there is a possibility of destructiveness in all metal circuits closer to the charged thunderclouds, but some lightning overvoltages are small and will not cause obvious damage to the equipment. However, the existence of overvoltage has an inevitable impact on the long-term service life of the equipment. Therefore, the difficulty of preventing lightning is far greater than that of direct lightning, and the cost of input is higher than that of direct lightning.

For the lightning protection of the system, from the two ways that may lead to lightning: power lines, signal lines, according to the characteristics of each type of equipment, the degree of lightning protection required, select the lightning protection products with appropriate cost performance, to achieve reasonable The price is fully protected. Ensure that the equipment is fully protected against direct lightning strikes and inductive lightning as well as line operating overvoltages.

Second, the specific lightning protection program

(1) Design basis

(1) GB50057-94 (2000 version) "Code for lightning protection design of buildings"

(2) JGJ/T16-92 "Electrical Design Code for Civil Buildings"

(3) GB 50174-93 "Design Specification for Electronic Computer Room"

(4)(99D562) "Installation of lightning protection facilities for buildings and structures"

(5) GB50343-2004 "Building Information System Lightning Protection Technical Specifications"

(6) IEC 1312-1-2-3 "Protection of lightning electromagnetic rush"

(II) On-site environmental analysis

Expressway toll stations have both strong electrical equipment and a large number of weak electrical facilities such as monitoring, communication, and sensing equipment. At the same time, they are mostly located in the suburbs, and the surrounding terrain is empty. The buildings are often nearby to the high point, and the power lines often have to Over the mountains and over the mountains, the information transmission and control lines need to cross complex geological levels, and the soil resistivity changes along the roads due to the roadbed and road construction of the expressway are highly vulnerable to lightning damage, especially inductive lightning and ground potential counterattacks. . However, at present, China has not paid enough attention to the lightning protection problem in highway design and construction. The lightning protection of highway supporting buildings and their electromechanical systems lacks unified planning and comprehensive design, and buildings, roadbeds, lighting, monitoring, communication, charging and other systems. It is often designed and constructed by a number of units, and there are many lightning protection weak links, and accidents that have been damaged by lightning strikes have occurred. Some parts of the light equipment were damaged by lightning, the system lost some functions, the whole system was paralyzed, and the economic losses were heavy. Especially after the highway toll station was struck by lightning, the toll system was not able to carry out the weighting, and the manual charging was not only slow, but also It will cause disputes or disputes because the charges cannot be objectively counted, resulting in blockage of vehicles at highway toll stations and affecting the smooth flow of expressways. With the continuous development of intelligent transportation, the wide application and integration of electronic equipment is increasing, and the degree of damage to lightning electronic equipment will continue to increase. Therefore, it is urgent to strengthen the lightning protection work of highway toll stations.

Highway toll stations include monitoring systems, charging systems, and communication systems. The comprehensive lightning protection of toll stations mainly includes lightning protection for building direct lightning protection, power supply and signal system of network charging system, monitoring system and communication system, and inductive lightning protection and various grounding treatments for auxiliary facilities. Since all the building (construction) of the toll station has basically implemented direct lightning protection lightning protection measures in the civil engineering, most of the direct lightning protection lightning protection measures are basically satisfied with the requirements of GB50057-94 "Lightning Protection Design Code for Buildings". This program does not involve direct lightning protection at the toll booth.

(three), specific programs

1. Network system lightning protection scheme

a. Network Center

The three-phase surge protector is installed in the main power supply of the building where the computer center computer room is installed. The flow capacity is 60KA, with lightning counter, box structure, and the large-flow flow module lightning arrester can be used. The three-phase surge protection of the computer center computer main switch is installed. The flow capacity is 40KA (if single-phase power is used, the single-phase power supply lightning protection device is selected). If there is installation space in the distribution box, you can use the module lightning protection computer or other equipment to take power. The specific model is: it can be directly installed on the network cabinet.

The ingress and egress lines of the network center need to be equipped according to the actual situation. The signal of the network incoming line is not required to be installed with a lightning arrester, but the fiber ribs must be well grounded; the ADSL broadband line enters the front end of the splitter and uses the incoming line as the dedicated line. Install the corresponding dedicated line lightning arrester. If all ports of the switch need lightning protection, multi-port computer network lightning arresters can be used. A total of 16 ports; the high-risk terminal connected to the switch is equipped with a single-port network lightning protection device.

b. External high risk network port

Most of the network lines from the computer center to the charging points are ordinary network cables. These cables are not well shielded due to their long distances. They are easily damaged by lightning induced voltage. The lightning risk of these lines is very high. It is necessary to install network signal lightning protection. The signal lightning protection device has a flow rate of 5KA, which can effectively protect the network line. This type of port corresponds to the high-risk port of the network center.

c. Grounding treatment

All arresters utilize their existing grounding facilities and no additional grounding. (The grounding resistance can meet the requirements according to the results of sampling and grounding resistance).

2. Monitoring system lightning protection scheme

The integrated lightning protection design of the monitoring system should take into account the environmental factors, the law of lightning activity, the importance of the system equipment, and the severity of the consequences of the disaster, and take corresponding protective measures.

(1) In the comprehensive lightning protection design, comprehensive design and maintenance should be carried out in accordance with the principles of comprehensive planning, comprehensive management, optimized design, multiple protection, advanced technology, economical rationality, regular inspection and random maintenance.

(2) The lightning protection design of the integrated lightning protection system shall be protected by direct lightning protection, equipotential bonding, shielding, reasonable wiring, grounding system and surge protection device. We must adhere to the guidelines of prevention and safety first.

(3) Monitoring and comprehensive lightning protection system should adopt different protection standards according to the location of the thunderstorm in the area and the location of the equipment placed in the lightning protection zone.

A. Monitoring center lightning protection plan

a. Power supply: It is recommended to install a three-phase AC power surge arrester (parallel, flow capacity 60KA) at the central power station of the center. As the first-level lightning protection, the box structure, you can also use the large-flow flow module lightning arrester center. Install a single-phase AC arrester at the power switch (parallel, flow capacity 40KA), model: as the second-level lightning protection (if three-phase power, select three-phase power lightning protection box), if there is installation space in the distribution box The module lightning arrester can be used as a power socket for each device to use a multi-function socket as the third-level lightning protection for the power supply to achieve the third-level lightning protection effect. If it is a rack-mounted PDU, it needs to be replaced with a lightning protection PDU. b. Signal line: Since the signal line introduced into the monitoring center only has video signal and pan/tilt control signal, all outdoor camera lead-in lines need to protect the video signal, and each video line adopts video signal arrester before entering the computer room video card. In order to achieve lightning protection, if there are more video signals, you can use the multi-channel video lightning arrester, which has 12 channels and 16 channels. For the PTZ control line, since the line adopts the coding control mode, the signals may have been merged before the introduction, so that only the remaining lines that will enter the computer after the merger are protected against lightning protection, and the corresponding logarithmic control line arrester can be used to protect the cloud. Station control signal.

c. Outdoor camera lightning protection

1) For outdoor cameras, video signal lightning arresters are used for each camera video line. For outdoor cloud platforms, control lines are used for each line.

Each camera gun power line is equipped with a camera gun-specific power supply arrester. If the camera power supply is 12 volts or 24 volts DC drawn from the control center, you can use the universal DC power supply lightning arrester or the power terminals at the front and rear ends. Anti-induction lightning protection.