Lightning Protection Professional Technical Knowledge In The Process Of Integrated Wiring
Today, with the development of economy and technology, the construction of smart cities, fiber-to-the-home, broadband China and other huge projects, the integrated wiring project is also accompanied by the progress of these projects, and the engineering volume is constantly increasing. In addition to the environmental factors around the wiring and the inherent quality of the equipment, the most important thing to consider in the design of the integrated wiring project is man-made damage and lightning damage. Today, let's take a look with you: it is necessary to understand the knowledge of lightning protection technology in the construction of integrated wiring engineering projects.
1. Lightning pulse current Iimp: an analog lightning current of 10/350μs waveform similar to natural lightning characteristics (peak value, charge amount and specific energy); the lightning current arrester must be able to discharge such lightning current several times without damage.
2. Nominal voltage UN: It is consistent with the rated voltage of the protected system; in the information technology system, this parameter indicates the type of protector that should be selected, and it marks the effective value of the AC voltage.
3. Rated voltage UC (maximum continuous operating voltage): It can be added to the specified end of the surge protector for a long time without causing changes in the characteristics of the surge protector and activating the maximum voltage effective value of the protection element; the UC value must be consistent with the protected The nominal voltage of the system matches and is within the specification limits of the system installation booklet.
4. Nominal current IN: the maximum working current through the specified end of the surge protector. Nominal discharge current isn: According to special classification test requirements, there is an inrush current peak value of 8/20μs waveform through the surge protector.
5. The maximum discharge current Imax: the surge current peak value of the 8/20μs waveform that the surge protector can discharge safely. Total discharge current: the total pulse current discharge capability of multi-phase surge protector or combined single-phase surge protector.
6. Voltage protection level UC: the maximum voltage of the protector in the following tests, the flashover voltage of 1.2/50μs (100%) standard lightning pulse; the flashover voltage of 1KV/μs slope; the residual voltage of rated discharge current; As far as the power system lightning arrester is concerned, according to the overvoltage classification of DIN VDE0110-1; 1997-04, it can be divided into one, two, three and four protectors, and the protection level determines its installation position; the protection level in the information system must be consistent with the protection level System and device compatibility matches.
7. Interruption capability (subsequent current arc extinguishing capability) If: the effective value of the main subsequent current that can be extinguished by the lightning arrester itself under UC, see EDIN VDE0675-6/A: 1996-03;
8. Short-circuit withstand capacity: when connected with the superior fuse, the maximum short-circuit current that the lightning arrester can withstand;
9. Overload protection: Overload protection equipment installed to prevent overheating damage to the protector due to overload of the main power supply line. e.g. fuse or fuse
10. Composite wave UOC: It is a wave of a 1.2/50μs open circuit voltage pulse and an 8/20μs short circuit current pulse sent by a mixed wave generator. The open circuit voltage is represented by UOC, and its value is mostly expressed in a class D lightning protection device.
11. N-PE protector: N-PE protector is a protector that can only be installed between N-PE wires.
12. Working temperature zone (nominal temperature zone): Indicates the temperature range in which the SPD can work normally.
13. Response time tA: It mainly reflects the action sensitivity of the special protection element in the protector. The breakdown time can change within a certain period of time depending on the slope of du/dt or di/dt.
14. Thermal tripping device: The protector with voltage control resistor (varistor) has a suspension tripping device, so when a certain temperature is reached (overload or failure), the protector can be cut off quickly connection to the mains to prevent fire. The function of the tripping device can be tested by simulating an overload of the protector.
15. Protection level: The protection level (IP number) of the packaging material of the lightning arrester is tested according to the standard of DIN EN60529 (VDE 0470 Part1).
16. Protection circuit: A protection circuit can be multi-level, and a protector can be composed of spark gaps, varistors and semiconductors. Decoupling elements are sometimes required between stages to achieve energy matching.
17. Data transmission rate VS: Indicates how many bits are transmitted in one second, unit: bps; it is the reference value for the correct selection of lightning protection devices in the data transmission system; the data transmission rate of lightning protection devices depends on the transmission mode of the system . The transmission rate is derived from the frequency bandwidth. The theoretical relationship between the transmission rate and the frequency bandwidth in the signal system is: Vs=2fG (Vs=1.25fG in practical applications)
18. Frequency bandwidth fG: The frequency bandwidth reflects the frequency response of the protector, that is, the frequency when the insertion loss is 3db. If other parameter changes are not considered, refer to the 50 ohm system frequency.
19. Return loss aR: Return loss indicates the proportion of the front wave being reflected at the protection device (reflection point), and is a parameter that directly measures whether the protection device is compatible with the system impedance.
20. Insertion loss aE: the ratio of the voltage before and after the protector is inserted at a given frequency. If other parameter changes are not considered, refer to the 50 ohm system frequency.
21. Discharge current at UN: continuous current from non-fault line to ground or line to other external conductive parts at nominal voltage UN.
22. Thunderstorm day: A thunderstorm day can be heard more than once in a day. Direct lightning strike: Lightning strikes directly on buildings, producing electrical effects, thermal effects and mechanical forces. Inductive lightning: When lightning discharges, electrostatic induction and electromagnetic induction are generated on nearby conductors, which may cause sparks between metal parts.
23. Intrusion of lightning waves: Due to the effect of lightning on overhead lines or metal pipelines, lightning waves may invade the house along these pipelines, endangering personal safety or damaging equipment.
24. Lightning electromagnetic pulse: the effect caused by the direct lightning strike and the nearby lightning strike as the interference source. The vast majority are disturbances through connecting conductors, such as lightning currents or partial lightning currents, potential rises in devices struck by lightning, and electromagnetic radiation disturbances.
25. Equipotential connection: Connect the conductive objects of separate devices with equipotential connection conductors or surge protectors to reduce the potential difference between them caused by lightning current.
26. Flaky thunder: The discharge between clouds is mostly flake lightning. Because the lightning of linear thunder is covered by the cloud body, the light of the lightning illuminates the upper cloud, and the lightning presents a flake of light. Flake mines have little effect on the ground.
27. Linear thunder: The discharge between the thundercloud and the earth mostly appears in the form of a line. Usually the lower part of the thundercloud is negatively charged, and the upper part is positively charged. Due to the negative electric induction of the thundercloud, a large amount of positive charges are induced on the nearby ground, thus forming a strong electric field between the ground and the thundercloud. Like the discharge between thunderclouds, when the charge density accumulated somewhere is very high, causing the electric field strength of the air to reach the critical point of ionization, it will trigger the linear lightning to strike. Ribbon lightning: It is a type of linear lightning. During the lightning process, there happens to be a horizontal strong wind blowing through the lightning channel, which separates the discharge channels of several lightning bolts, and the lightning channel widens as seen by the naked eye.
28. Spider lightning: Spider lightning specifically refers to the spectacular discharge phenomenon with large-scale horizontal development and multi-branched discharge channels observed near the cloud base during the dissipating phase of thunderstorm clouds or the layered rainfall phase. The reason why it is called "spider" lightning is that this kind of discharge develops at a significantly slower speed than ordinary lightning under the cloud and advances in the form of multi-level bifurcations. The development characteristics of each channel are similar to the crawling of a spider. The spider-like lightning seen with the naked eye is very spectacular. According to observation experience, this kind of lightning generally does not appear often. At present, there is no systematic observation and statistical results. During the dissipating period of thunderstorm clouds that are developing vigorously in southern my country, this phenomenon of spider discharge has been observed with ordinary cameras.
29. Ball lightning: referred to as ball thunder and ball flash. The ball mine is a colorful flame-like sphere, usually in the form of an orange or red sphere with a diameter of 100-300 mm, sometimes it may be blue, green, yellow or purple, and the largest diameter can reach 1000 mm; ball mines exist The time is a few hundredths of a second to a few minutes, usually between 3 and 5 seconds, and the radiation power is less than 200W.
When the ball mine falls from the sky, the sound is small, sometimes silent, and sometimes it makes a hissing sound. Only when it encounters objects or electrical equipment during the fall and jump will it make a deafening explosion. The object is destroyed in the explosion and produces the smell of ozone, nitrogen dioxide or sulfur.
After the ball mine falls vertically from the sky, it sometimes jumps up and down horizontally at a speed of 1 to 2 meters per second at a height of about 1 meter from the ground; sometimes the ball mine rolls at a height of 0.5 to 1 meter from the ground, or suddenly It rises 2 to 3 meters, so it is often called a rolling mine among the people. Ball mines often enter the room through holes in buildings or unclosed doors and windows, or roll into buildings along vertical building shafts, and most of them disappear when they encounter charged objects.
30. Bead-shaped lightning: a rare kind of lightning, some people think it is composed of ball mines. Lightning can be divided into intra-cloud lightning, inter-cloud lightning (cloud lightning), cloud-to-ground lightning (ground lightning) and so on according to the spatial location where it occurs. Among them, ground lightning is divided into landing mines and direct lightning strikes, which are the main research objects of lightning protection.