Based on Maxwell's electromagnetic field theory, the high-frequency electronic equipment in the center body of a satellite communication earth station's antenna feeder has been repeatedly damaged by lightning, and it is proposed that the lightning protection system of the satellite communication earth station is a systematic project. Lightning protection measures. A simple lightning strike solution is proposed for the lightning protection of a satellite station.
Keywords satellite earth station electronic equipment lightning protection
1. Brief description of satellite communication Satellite communication is radio communication with artificial satellites as relay stations. It works in the microwave band. Satellite communication has become an important modern communication method and has been widely used at home and abroad. During the Gulf War, the United States used satellite communications to handle about 90% of the communications business in the US military theater. The advantage of satellite communication is that the communication distance is long, and the cost of building a station is independent of the communication distance. It works in broadcast mode, which is convenient for multiple access, large communication capacity, many types of services that can be transmitted, stable and reliable performance, no geographical restrictions, and flexibility. Features. China's satellite communication is developing rapidly. Fixed satellite communication earth stations, vehicle-mounted satellite communication earth stations, portable satellite communication earth stations, mobile satellite communication earth stations, etc. are widely used in domestic military and civil satellite communication networks. With the development of satellite communication technology and the demand for satellite communication services, domestic satellite communication has developed from a single C-band to C, UHF, Ku multi-band satellite communication. In earthquake relief, portable satellite communication earth stations and mobile satellite communication earth stations have fully played its role. This article only discusses the lightning protection of a fixed satellite communication earth station on the ground.
2. The electronic equipment of a satellite station was damaged by lightning several times, and a lightning rod was installed on the roof of the computer room of a satellite communication earth station. The height of the ground is about 27 meters to protect the communication equipment of the computer room. In the antenna field, three tower lightning rods were placed side by side, about 32 meters above the ground. To protect the antenna field of the antenna feeder system level and the high-frequency design of the antenna tail 
Figure 1 The antenna of a high-frequency electronic device of a satellite station has been damaged by lightning
Equipment (low noise amplifier LNA and high power amplifier HPA). Over the past few years, the high-frequency part of the antenna feed system has been damaged by lightning many times, not in this antenna, but in another antenna. Why can't the tower lightning rod of about 32 meters high be used to protect the high frequency electronic equipment of 2-5 meters high and be damaged by lightning? The antenna of the high-frequency electronic equipment of a satellite station successively damaged by lightning is shown in Figure 1. In Figure 1, the two low-noise amplifiers (LNA) in the center body of the tail of the right C-band antenna are damaged during a lightning strike, and the two Ku-band antenna high-frequency equipment in the middle and left are damaged during another lightning strike. The following discusses the generation of lightning and lightning protection.
3. Lightning
3.1 Lightning is a rapidly changing electromagnetic field. There are several views on lightning, one is a constant voltage circuit, another is a constant current circuit, and the third is a rapidly changing electromagnetic field. The electromagnetic waves it radiates are extremely wide, including the ratio Light waves with higher microwave frequencies. The author agrees with the third viewpoint that lightning is a rapidly changing electromagnetic field. The electromagnetic field energy of lightning is converted into light energy, sound energy and heat energy of objects in the electromagnetic field.
3.2 The formation of lightning The formation of lightning. Due to the atmospheric space field, the clouds separate and become charged. The distribution of charge in the thundercloud is uneven, forming multiple accumulation centers. Whether in the cloud or between the cloud and the ground, the electric field strength is inconsistent. When the electric field strength in the densely charged area of ​​the cloud is large to a certain extent, the cloud will start the pilot discharge. Pilot, when the pilot meets the oncoming pilot, it forms an ionization channel from the cloud to the ground. It is the main discharge stage of lightning, accompanied by lightning flashes. The feature was struck by lightning. Simply put, when a charged cloud layer gradually accumulates a sufficient amount of charge, it will break through the air, produce lightning, and form lightning.
4. Lightning rod
4.1 The lightning rod is a lightning rod The lightning rod is actually a lightning rod. Russia calls it the "air-termination device", and the United States and Britain call it the "conductive pin". Lightning protection devices that receive direct lightning strikes are called lightning receptors, for example: lightning protection belts, lightning protection nets, lightning protection wires, Faraday cages, etc. The lightning rod is a type of lightning receptor. The protection function of the lightning rod is to intercept the lightning and make it hit itself, so that the building is protected from direct lightning strikes. The lightning rod safely guides the energy of the lightning into the ground along the tower or down conductor. The protection scope of the lightning rod adopts the rolling ball method. The upper space of the lightning rod is its lightning-inducing airspace, and the lower space is its protection range, so that it is not directly struck by lightning.
4.2 Application environment of lightning rod
4.2.1 Lightning rod lightning protection should not be used in mountainous buildings. Thunderstorms on slopes below the mountain often produce lateral lightning strikes. Lightning protection belts or lightning protection nets should be used.
4.2.2 Lightning rod lightning protection should not be used in high-rise buildings according to the "lightning protection" specification, the height of the lightning rod is greater than 60 meters, the protection range of the rolling ball method is invalid. There is a space above the overhead lightning rod that may itself be struck by lateral lightning (referred to as the side impact area on the needle bar). The elevated lightning rod has a strong ability to induce lightning, so that the lightning strike density of the ground near the elevated lightning rod is greater than the average lightning strike density there (called the lightning flash zone). Lightning protection belts or lightning protection nets should be used as far as possible for lightning protection. Only antennas and other short-needle lightning protection are used.
4.2.3 Lightning rod should be used for lightning protection of small buildings in plain areas
5. Lightning induction high voltage and lightning electromagnetic pulse 5.1 Lightning induction high voltage and lightning electromagnetic pulse lightning rod can prevent direct lightning and protect buildings. However, with the development of science and technology, a large number of electrical, electronic and microelectronic devices are now used. During thunder and lightning, electromagnetic induction and lightning electromagnetic pulses are generated around the discharge channel to cause the lightning high voltage induced by the power line, signal transmission line, and antenna feeder to cause discharge through these lines, damaging electrical, electronic, and microelectronic equipment.
5.2 Lightning protection inductors use high voltage and lightning electromagnetic pulses and use surge protectors (SPD).
The surge protector is installed in the external connection line (power line, signal line, antenna feeder line) of the electronic equipment, and the lightning overvoltage and overcurrent are discharged to the ground to protect the equipment. Lightning protection device is mainly composed of discharge gap, discharge tube, high frequency diode, varistor, transient diode, thyristor high and low pass filter according to different frequency, power, transmission rate, impedance, standing wave, insertion loss, bandwidth, voltage, current And other requirements, made various series of surge protectors.
5.2.1 Waveguide shunt-type electronic surge arresters Traditional surge arresters cannot be considered, irreconcilable, and mutually restrictive among the operating frequency (F), withstand power (W), and current capacity (I). As we all know, more than 99% of the energy of lightning shock waves is distributed in the frequency domain below 100KHz, and the energy of the useful signal wave is distributed in the frequency domain of more than several hundred kilohertz. Therefore, it is entirely possible to use high or low pass filter combinations composed of concentrated or distributed parameter circuit elements Network (passive, reciprocal network). Lightning waves and useful signals are shunted so that lightning waves enter the ground and useful signals are transmitted normally.
6. The electronic information lightning protection system must have a qualified grounding grid. There are various methods for grounding systems. The better one is to choose the low-resistance non-metal grounding module of Zhongguang Lightning Protection Company. The advantage is that it is suitable for soil with high soil resistivity, highly corrosive soil, and frozen soil in alpine regions. An outpost in Nathula, Tibet, is 4,500 meters above sea level and belongs to alpine volcanic stone ground, as shown in Figure 2. In the past, the lightning protection network of electronic equipment or barracks buildings in this area has been made many times to 960Ω and low to 180Ω. After multi-car dirt and drag reducing agent, the lowest can only be 53Ω. Far from reaching the national standard requirements of less than 4Ω. Adopt Zhongguang Lightning Protection Company's low resistance non-metal grounding module. After calculation, 60 modules were used. After testing with the Japanese instrument 4102 type ground resistance instrument, the ground network resistance was reduced from the original 53Ω to 3.5Ω, reaching the national standard of lightning rod ground network resistance of less than 10Ω and equipment ground network resistance of less than 4Ω. Overcame the problem of a lightning protection ground network that has long been unresolved in the high-altitude volcanic rocky ground in Tibet.
Figure 2 The stony ground of Nadula Volcano in Tibet at an altitude of 4500 meters
7. Comprehensive lightning protection In recent years, lightning protection has developed from a Franklin-type lightning rod to prevent direct lightning strikes to a new stage of comprehensive lightning protection engineering. The electronic information lightning protection system should be a comprehensive lightning protection project. It consists of direct lightning protection measures, equipotential bonding measures, shielding measures, standardized comprehensive wiring, design and installation of SPD, and perfect and reasonable grounding system.
8. Investigation on the causes of lightning strikes Based on the aforementioned six elements of comprehensive lightning protection, the causes of lightning strikes were investigated. And mainly carried out key investigations against direct lightning strikes, induction lightning strikes and ground nets. The resistance of the grounding network conforms to the "Code". The three tall tower lightning rods are normal. The equipment in the power distribution room, main room, and antenna field high power amplifier equipment are normal. The power distribution room is protected against lightning in the first class, the host room is protected against lightning in the second class, and the high power amplifier room in the antenna field is protected against lightning in the third class. What was damaged by the lightning was the electronic equipment of 2 KU band antennas, whose working frequency was 12GHZ frequency band. After investigation, the power lines, signal lines and antenna feed lines connected to the electronic equipment are not equipped with lightning protection devices (ie SPD) for preventing lightning strikes. The distance between the lightning protection tower and the transmission cable is less than 2 meters.
The lightning rod is a lightning receptor, that is, a lightning arrester. It can prevent direct lightning, but not induction lightning. A good ground network can make the lightning current enter the ground through the lightning rod, tower or down conductor. Lightning waves generated by lightning are rapidly changing electromagnetic fields, which will induce overvoltages in signal lines, power lines, and antenna feed lines, and will enter electronic equipment at both ends of the line. The changed induced electromagnetic field will also induce overvoltage in the signal line, power line, and antenna feed line, and will be introduced into the electronic equipment at both ends of the line. If the electronic equipment at both ends of the above line is not equipped with a surge protector, the induced overvoltage current will damage the electronic equipment. For lightning protection of electronic equipment, only the lightning rod is installed, and no lightning protection device against induction lightning strike is installed. The higher the lightning rod, the easier it is to bring in distant lightning, which increases the number of induced lightning strikes, and does not install anti-induced lightning strike devices, which is tantamount to leading the lightning to hit electronic equipment. Therefore, both the design unit and the construction unit for the lightning protection engineering of electronic equipment should be units with design qualifications and construction qualifications. The construction process should be strictly supervised and checked, and strictly checked and accepted upon completion. Check and maintain after completion.
9. Conclusion In summary, the lightning wave of lightning is a rapidly changing electromagnetic field. The lightning protection system of the satellite earth station shall adopt comprehensive lightning protection measures. That is, direct lightning protection measures, equipotential bonding measures, shielding measures, standardized comprehensive wiring, design and installation of SPD, and perfect and reasonable grounding system. The lightning rod is a lightning rod, which can prevent direct lightning strikes, but it also leads the lightning, which increases the number of induced lightning strikes of electronic equipment. Without the installation of anti-inductive lightning strike devices, electronic equipment will be more easily hit by lightning. The design and construction of lightning protection projects should be conducted by units with design qualifications and construction qualifications. Strict supervision and control shall be conducted during construction, and strict acceptance shall be carried out upon completion. The lightning protection system of a satellite station should be transformed. Measures to prevent direct lightning strikes can be appropriately modified. The location, height and number of lightning towers can be recalculated and constructed. Surge protectors against induction lightning strikes should be installed at both ends of the power lines, signal lines, and antenna feed lines from the antenna field to indoor equipment. (The reconstruction of Xiangxi Lightning Protection into a program is described in another article).
References [1] "Lightning Protection Technical Specifications for Building Electronic Information Systems" (GB50343-2004)
[2] Wang Deyan, Waveguide Shunt Theory China Anti-Radar 2003 No. 6: 61-68
[3] Yu Hao, Physical Concept of Lightning Protection Technology in the 21st Century, China Lightning Protection Shower, 2003, Issue 2: 6-9
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