Lightning Protection Measures for Microwave Communication Stations
2023-11-07 13:12:03
1, lightning characteristics:
Lightning is an atmospheric physical phenomenon. The formation of a lightning must have three conditions. One is that there is a sufficiently high positive and negative charge potential difference in the atmosphere. When the electric field in the sky is enhanced to a point where the potential gradient is greater than 3×10 6 V/m, a breakdown discharge, ie, lightning, occurs. Lightning can occur between the cloud and the cloud or between the cloud and the earth. A lightning consists of several discharge pulses. Each discharge pulse has two phases: the preparation phase (pilot process) and the return stroke phase (main discharge process).
According to IEC 1312-1, the lightning current can be regarded as being composed of the first lightning current if (10/350 μs) and the subsequent lightning current is (0.25/100 μs).
IEC TC81 (Protection Commission for Lightning Protection) uses an oblique triangle waveform with an inrush current of 10/350μs called lightning current (Lightning) and an 8/20μs impulse current called surge current (Surge). Both are different concepts. The community calls it direct lightning and induced lightning. Direct lightning and induced lightning are two forms of lightning strikes.
Direct lightning is the lightning current that directly hits an electrical device or circuit and causes a powerful lightning current. It is discharged into the ground by being hit by an object.
Inductive lightning refers to the occurrence of electrostatic induction or electromagnetic induction in a device or circuit when a thunderstorm occurs in the vicinity of a building or system. Thundercloud progresses from the pilot discharge process to the main discharge process. Lightning overcurrent or overvoltage due to charge release on the object. .
The main parameters of lightning are as follows:
Thundercloud charge 20-100C
Ground electric field strength>30kV/cm
Lightning current amplitude 20kA
The main energy of the lightning current frequency is concentrated in 100Hz-1kHz, the highest frequency can reach 106Hz.
2. The main ways of lightning intrusion For microwave communication stations, full consideration must be given to lightning intrusion methods. Only in this way can we conduct targeted lightning protection. The main methods of lightning intrusion are:
(1) Lightning directly hits the lightning rod or other lightning protection device on the microwave tower. The lightning current flows into the ground through the iron tower and the ground network. The ground potential rises, counterattacking the equipment and damaging the communication equipment;
(2) Lightning is introduced into the engine room via the antenna feeder, and after the rack enters the ground, the induced voltage (flow) is generated on the coaxial cable, which invades and damages the microwave engine.
(3) The external audio cable of the communication room is struck by lightning, and the overvoltage (flow) of the audio cable invades the communication device;
(4) The power line is struck by lightning, and lightning strikes the AC and DC power distribution system and the rectifier system through the transmission line, damaging the power system;
(5) When the lightning receiving device outside the communication room receives lightning, a powerful lightning current flows through the down conductor to the ground to discharge a high-frequency electromagnetic field around the communication room. This high-frequency electromagnetic field is in the form of coupling and conduction, causing various wires around it to generate inductive current (pressure) invasive devices.
The situation of lightning strikes is diversified. The above does not represent all of them. Each communication station must carefully analyze the various possibilities of lightning strikes and take the initiative to prevent lightning, according to its own actual conditions.
Lightning is an atmospheric physical phenomenon. The formation of a lightning must have three conditions. One is that there is a sufficiently high positive and negative charge potential difference in the atmosphere. When the electric field in the sky is enhanced to a point where the potential gradient is greater than 3×10 6 V/m, a breakdown discharge, ie, lightning, occurs. Lightning can occur between the cloud and the cloud or between the cloud and the earth. A lightning consists of several discharge pulses. Each discharge pulse has two phases: the preparation phase (pilot process) and the return stroke phase (main discharge process).
According to IEC 1312-1, the lightning current can be regarded as being composed of the first lightning current if (10/350 μs) and the subsequent lightning current is (0.25/100 μs).
IEC TC81 (Protection Commission for Lightning Protection) uses an oblique triangle waveform with an inrush current of 10/350μs called lightning current (Lightning) and an 8/20μs impulse current called surge current (Surge). Both are different concepts. The community calls it direct lightning and induced lightning. Direct lightning and induced lightning are two forms of lightning strikes.
Direct lightning is the lightning current that directly hits an electrical device or circuit and causes a powerful lightning current. It is discharged into the ground by being hit by an object.
Inductive lightning refers to the occurrence of electrostatic induction or electromagnetic induction in a device or circuit when a thunderstorm occurs in the vicinity of a building or system. Thundercloud progresses from the pilot discharge process to the main discharge process. Lightning overcurrent or overvoltage due to charge release on the object. .
The main parameters of lightning are as follows:
Thundercloud charge 20-100C
Ground electric field strength>30kV/cm
Lightning current amplitude 20kA
The main energy of the lightning current frequency is concentrated in 100Hz-1kHz, the highest frequency can reach 106Hz.
2. The main ways of lightning intrusion For microwave communication stations, full consideration must be given to lightning intrusion methods. Only in this way can we conduct targeted lightning protection. The main methods of lightning intrusion are:
(1) Lightning directly hits the lightning rod or other lightning protection device on the microwave tower. The lightning current flows into the ground through the iron tower and the ground network. The ground potential rises, counterattacking the equipment and damaging the communication equipment;
(2) Lightning is introduced into the engine room via the antenna feeder, and after the rack enters the ground, the induced voltage (flow) is generated on the coaxial cable, which invades and damages the microwave engine.
(3) The external audio cable of the communication room is struck by lightning, and the overvoltage (flow) of the audio cable invades the communication device;
(4) The power line is struck by lightning, and lightning strikes the AC and DC power distribution system and the rectifier system through the transmission line, damaging the power system;
(5) When the lightning receiving device outside the communication room receives lightning, a powerful lightning current flows through the down conductor to the ground to discharge a high-frequency electromagnetic field around the communication room. This high-frequency electromagnetic field is in the form of coupling and conduction, causing various wires around it to generate inductive current (pressure) invasive devices.
The situation of lightning strikes is diversified. The above does not represent all of them. Each communication station must carefully analyze the various possibilities of lightning strikes and take the initiative to prevent lightning, according to its own actual conditions.
Led Night Light,Projection Small Night Light,Led Star Projector Light,Rechargeable Night Light
Shenzhen You&My Electronic Technology Co., Ltd , https://www.ymledtrade.com