How should the building be lightning protection?

Lightning is an inevitable natural disaster, and lightning is active at all times on the planet. Therefore, it is necessary to understand the laws of lightning and to master correct preventive measures and self-rescue methods. There are four main types of lightning: direct lightning, inductive lightning, lightning intrusion, and spherical lightning. The lightning protection design and installation of buildings shall be considered as a whole for external lightning protection devices, internal lightning protection devices, the environment outside the building and the lightning protection devices to the whole community. This is one of the important issues in the transformation of modern lightning protection design concepts.

Lightning is an inevitable natural disaster, and lightning is active at all times on the planet. According to statistics, 1800 thunderstorms per second, with 600 lightning strikes, 100 of which were shot down on the ground, causing damage to buildings, power generation, communications and video equipment, causing fires, causing injuries to people, animals, and annual economic losses. About 1 billion US dollars, more than 3,000 deaths. China is also a country with frequent lightning disasters. Therefore, it is necessary to understand the laws of lightning and to master correct preventive measures and self-rescue methods. First, the formation and characteristics of lightning 1. The formation of lightning is a phenomenon of discharge in the atmosphere. During the formation of lightning, some parts of it accumulate positive charges, and another part accumulates negative charges. When these charges accumulate to a certain extent At the level, a discharge phenomenon occurs. Some of this discharge is between the clouds and the clouds, and some between the clouds and the earth. The latter type of discharge is also a lightning strike that destroys buildings, damages electrical equipment, and injures people and animals. This discharge time is short, generally about 50-100 microseconds, but the current is exceptionally strong, reaching tens of thousands of amps to hundreds of thousands of amps. When the discharge produces intense light, this is lightning. When lightning strikes, it will release a lot of heat energy, which can instantly raise the temperature of the air by 1-2 million degrees, and the pressure of the air can reach 70 atmospheres. Such a large amount of energy has great destructive power, which often causes fires and humans and animals. casualties. The principle of lightning generation: When dust, ice crystals and other substances in the air roll and move in the clouds, after some complicated processes, these substances are respectively charged with positive and negative charges. Then, because the same substance is of the same quality, it carries the same charge. After motion, a heavier mass of material with the same charge will reach the lower part of the cloud (generally a negative charge); a lighter mass with the same charge will reach the upper part of the cloud (generally a positive charge). Thus, the collection of isotropic charges forms some charged centers, and when the air between the oppositely charged centers is broken by its strong electric field, an inter-cloud discharge is formed. When the negatively charged cloud layer is close to the ground, the protrusions, metal, etc. of the ground will be induced with a positive charge. As the electric field gradually increases, the thundercloud forms a downward leader downward, and the ground object forms an upward flash. When they meet, they form a discharge to the ground. 2. Main features of lightning: (1) Large inrush current. Its current is up to tens of thousands to hundreds of thousands of amps; (2) the time is short. Generally, lightning strikes are divided into three stages, namely, pilot discharge, main discharge, and residual light discharge. The whole process generally does not exceed 60 microseconds; (3) the frequency is high. The gradient of lightning current varies greatly, some up to 10 kA/μs; (4) The high impact voltage, the alternating current generated by the powerful current, the induced voltage can reach hundreds of millions of volts. Second, the types of lightning, hazards and protection There are four main types of lightning: direct lightning, inductive lightning, lightning intrusion, spherical lightning. (1) Direct lightning: 1. Direct lightning strikes mainly damages the high-rise building, which is the rapid discharge phenomenon between the charged cloud layer (Thundercloud) and buildings, other objects, the earth or lightning protection devices, and the resulting electricity A series of damaging effects such as effects, thermal effects or mechanical forces. Refers to the rapid discharge between the charged cloud layer and a certain point on the earth, mainly damaging buildings, electronic equipment and people in buildings. The peak voltage of a direct lightning strike can usually reach tens of thousands of volts or even millions of volts, and the current peak can reach tens of thousands to hundreds of thousands of amps. The reason is very destructive. The main reason is that the energy contained in the thundercloud is extremely short. Time (which usually lasts only a few microseconds to a few hundred microseconds) is released, and in terms of instantaneous power, it is huge. 2, direct lightning protection against direct lightning is mainly based on the International Electrotechnical Commission IEC1312_1 ~ 3 "Lightning electromagnetic pulse protection", "electronic computer room design specifications", "electronic equipment lightning strike guidelines", "building lightning protection design specifications "Wait. Generally, a lightning rod, a lightning protection belt, a lightning protection line, a lightning protection net or a metal object is used as a lightning receptor, and the lightning current is received, and guided by a metal conductor as a down conductor to a grounding device buried in the earth to disperse flow. Then vent to the ground. (2) Inductive lightning: 1. Inductive lightning is the natural enemy of indoor weak electricity equipment. During the direct lightning discharge process, the powerful pulse current generates electromagnetic induction to the surrounding wires or metal objects, causing high voltage and flashing, which mainly damages the electronic equipment in the building. It is the moment of lightning discharge, the phenomenon of static induction and electromagnetic induction generated by nearby conductors. Electrostatic induction: Due to the action of thunderclouds, the nearby conductors sense and accumulate a large number of bound charges opposite to the thunderclouds. When the thundercloud main discharges, the charge in the thunder pilot channel is quickly neutralized, which is in the vicinity of the thundercloud. The bound charge of the opposite polarity of the thundercloud is released, forming a free charge, which produces a high potential if it is not leaked into the ground. Electromagnetic induction: Due to the rapid change of lightning current (transient pulse), a transient strong electromagnetic field is generated in the surrounding space, which induces a high electromotive force on the nearby conductor. 2. Protection against inductive lightning (1) Power supply lightning protection According to the requirements of building construction, the power distribution system power supply lightning protection should adopt integrated protection. Because the design ideas of the lightning arrester manufacturers are different, the performance characteristics of the lightning arresters are not exhausted. Consistent. (2) Signal system lightning protection is the same as power supply lightning protection. The lightning protection of communication network mainly uses lightning arrester for communication. At present, computer remote networking often adopts telephone lines, dedicated lines, X.25, DDN and frame relay, etc. Communication network equipment is mainly MODEM, DTU, router and remote interrupt controller. Generally, the communication lightning arrester is selected according to the type of the communication line, the communication frequency band, the line level, etc., and the communication lightning arrester is connected in series on the communication line. (3) The purpose of the equipotential bonding equipotential bonding is to reduce the potential difference between the metal parts and the systems in the space where lightning protection is required. Prevent lightning strikes. Connect the main metal casing in the equipment room, UPS and battery box metal casing, metal floor frame, metal door frame, facility piping, cable tray, aluminum alloy window, and connect to the nearest equipotential bonding with the shortest route. With or with other metal objects that have been equipotentially connected, the conductors are connected to each other as many times as possible. (4) Metal shielding and repeated grounding On the basis of the above measures, effective shielding and repeated grounding should be adopted to prevent overhead conductors from directly entering the building and equipment room, as much as possible, and using metal conduits. Shielding, shielding metal pipes are repeatedly grounded before entering the building or machine room, and maximally attenuating the introduction of lightning high voltage from various wires. (3) Lightning intrusion into the lightning wave The lightning wave is a lightning wave that rapidly propagates along the line or pipeline along the impact voltage generated on the overhead line or in the aerial metal pipeline due to lightning strikes. Its propagation speed is 3x108m/s. Lightning intrusion waves can destroy the insulation of electrical equipment, causing high voltages to suffocate people and causing serious electric shocks. There are many lightning accidents caused by lightning invading waves. In low-voltage systems, such accidents account for about 70% of total mine accidents. For example, in thunderstorm days, indoor electrical equipment suddenly explodes or is damaged by fire. It is a kind of accident that people suddenly use electric appliances or make electric shocks when they call. In order to prevent lightning intruding waves from entering the room along the low voltage line, the low voltage line is preferably powered by an underground cable and grounded the metal sheath of the cable. When using overhead line power supply, install a set of low-pressure valve type arrester or 2~3mm protection gap in the outdoor, and ground it together with the insulator iron foot. The grounding device can be used in conjunction with the grounding device of the electrical equipment. The grounding resistance must not be greater than 5 to 30 Ω. The valve type arrester is mounted on the attractive end of the protected object. The upper end is connected to the line and the lower end is grounded. Normally, the gap of the arrester remains insulated and does not affect the operation of the system. When a high-voltage shock wave strikes along the line due to lightning strikes, the arrester gap penetrates and grounds, thus forcibly cutting off the shock wave, and then entering the voltage of the protected object. Only the residual current generated by the lightning current through the arrester and its leads and grounding devices. After the lightning current passes through the gap of the arrester, the insulation state is restored, so that the system can operate normally. (4), spherical mine: in the thunderstorm season with frequent lightning, occasionally find the "fireball" of red, gray, purple, blue, the diameter is generally ten to tens of centimeters, or even more than 1 meter; sometimes it falls from the sky, and then Moving horizontally in the air or along the ground, sometimes panning and sometimes rolling, entering the room through chimneys, open doors and windows and other gaps, or disappearing silently, or making a sound of a wire, or a violent explosion, so people used to call it "Spherical mine". More rare. It is best not to open the doors and windows during thunderstorms, and install metal protection nets with a mesh eye of no more than 4 square centimeters and a thickness of about 2 to 2.5 mm in the air flow of chimneys, ventilation ducts, etc., and then make a good grounding. In the lightning protection standards for international buildings (IEC/TC-81) and China's "Lightning Protection Design Codes for Buildings", there is no provision for the protection of ball mines. It is not difficult to protect the ball mine. In terms of protective ball lightning measures, it is best to use a cage lightning protection net. If the cage lightning protection network condition is not met, install the metal gauze on the windows and doors of the building and ground it; Unnecessary holes on the wall of the object; the upper part of the chimney and the outlet pipe should be installed with barbed wire and grounded; the chimney and vent pipe of the warehouse and factory building where the flammable or explosive objects are stored or damaged should be equipped with a flame arrester and grounded. In particular, measures to protect the ball should be taken for important buildings under tall trees. Third, the overall structure of building lightning protection The overall performance of lightning protection is reflected in the lightning protection design and installation of the building, the internal lightning protection device and the external lightning protection device should be considered as a whole. The overall concept outside the building refers to a comprehensive lightning protection plan for a courtyard, a community and the surrounding environment. At the same time, it cannot violate the requirements of the community planning. For example, whether the installed lightning rod tower affects the beauty of the community, the lightning rod used. Whether the lightning protection belt or lightning protection net matches the facade of the building and whether the low-rise buildings can be protected by lightning protection devices on tall buildings or tall chimneys. The grounding device should also be considered comprehensively. For example, can buildings with close proximity share the grounding body, whether the underground pipe network can use a part of the grounding body, and whether it can be created in a large courtyard or community for future integrated grounding. Equipotential bonding conditions and so on. Therefore, lightning protection design and installation of buildings should consider the overall lightning protection device, internal lightning protection device, the environment outside the building and the lightning protection device to the whole community. This is one of the important issues in the transformation of modern lightning protection design concepts.

Dissolved Oxygen Controller

Dissolved oxygen controller is a device used to monitor and control the dissolved oxygen content in water. Dissolved Oxygen Controllers require a Dissolved Oxygen Sensor to be connected. The sensor is used to measure the dissolved oxygen concentration in the water and transmit the data to the controller. The DO controller controls the dissolved oxygen content in the water body by adjusting other parameters according to the preset dissolved oxygen target range. The dissolved oxygen meter has 2 relays, which can set the closing value and breaking value, and 2-way 4-20mA current output, which can control the device more accurately.
The specific control method depends on the requirements of the application and the design of the system. A common control method is to control the dissolved oxygen content by adjusting the amount of aeration. Aeration is the process of increasing dissolved oxygen by passing air or oxygen through the water. The dissolved oxygen controller can automatically adjust the aeration amount or stirring intensity according to the dissolved oxygen data measured by the sensor to keep the dissolved oxygen concentration within a predetermined range.

It should be noted that the control of dissolved oxygen level involves many factors, including water body temperature, pressure, salinity and other water quality parameters. Daruifuno's dissolved oxygen controller supports compensation function. The dissolved oxygen controller also has RS485 output and time history recording function, and supports various installation methods.

dissolved oxygen controller


Dissolved Oxygen Controller,Dissolved Oxygen Meter, Dissolved Oxygen transmitter

Suzhou Delfino Environmental Technology Co., Ltd. , https://www.daruifuno.com