What Is a Lightning Protection System?
AC power supply lightning protection modules are suitable for power supply protection in power distribution rooms, power distribution cabinets, switch cabinets, AC and DC power distribution panels, communications, electronics, electricity, networks, energy, railways, highways and other systems; · Outdoor input in buildings Power distribution boxes and building-level distribution boxes; · For low-voltage (220 / 380VAC) industrial grids and civil grids; · Signal lightning arresters for overvoltage protection against line intrusion; lightning rods for direct lightning protection; Medium is mainly used for the three-phase power input or output terminal in the power supply screen of the automation room and the main control room of the substation.
Lightning protection
AC power supply lightning protection modules are suitable for power supply protection in power distribution rooms, power distribution cabinets, switch cabinets, AC and DC power distribution panels, communications, electronics, electricity, networks, energy, railways, highways and other systems; · Outdoor input in buildings Power distribution boxes and building-level distribution boxes; · For low-voltage (220 / 380VAC) industrial grids and civil grids; · Signal lightning arresters for overvoltage protection against line intrusion; lightning rods for direct lightning protection; Medium is mainly used for the three-phase power input or output terminal in the power supply screen of the automation room and the main control room of the substation.
- Chinese name
- Lightning protection
- Foreign name
- anti-thunder
- Scope of application
- Communication base station, 4G base station, lightning protection ground network reconstruction
- Principle
- Intercept by composition
- Classification
- Grounding body and ground wire
(1) Formation of Thunder Cloud
The generation of thunder and lightning began with the generation of thunder clouds. In fact, there are several types of clouds related to thunder and lightning, such as stratocumulus, rain stratum, cumulus, and cumulonimbus. The most important is cumulus cloud, which is thundercloud. Thunder cloud is a huge, opaque and charged dark cloud cloud composed of water droplets, ice crystals and gas dust over the atmosphere. The fundamental reason for its formation is the movement of water vapor. With the continuous development and accumulation of thunderclouds, lightning and thunder phenomena will be caused. This is thunderstorms.
1) Classification of thunderstorms
There are two main types of thunderstorms: frontal thunderstorms and thermal thunderstorms.
Frontal thunderstorms are due to the fact that when two air masses flowing on the surface meet, cold air masses flow below the hot air masses due to their high density, forming a relative movement at the interface between the two and lifting the hot air masses sharply. And vortices so that cumulus clouds will form. At this time, if the temperature of the hot air mass is high enough and the water content is sufficient, a huge thunderstorm cloud can be formed.
Thermal thunderstorms occur in the mountains. Due to sunlight, the temperature of the hills and the ground rises, and the hot air flows to the sky due to the low density. The temperature of nearby trees, lakes, and rivers is lower, and the relatively cool air around them is higher and lower to the hills. The area is concentrated, and at the same time, these air currents are heated by the high temperature of the hill surface and flow into the sky, thus forming a thermal thunderstorm.
2) The electrification mechanism of cumulonimbus
There are three main theories of the cumulus cloud electrification mechanism:
Water-absorbing charge effect. There is an electric field in the atmosphere that moves downwards, causing the positive and negative ions of the air to move downward and upward, respectively. Neutral water droplets are also subject to polarization in the electric field, with a negative charge at the upper end and a positive charge at the lower end. When a large water droplet falls, its lower end absorbs negative ions and repels positive ions. Because the large water droplet drops fast, the negative charge on its upper end has no time to absorb the positive ions above it, so the entire water droplet is negatively charged. The small water droplet is carried upwards by the air flow, and the polarized negative charge at the upper end will absorb positive ions, so the small water droplet is positively charged.
Freezing effect of water droplets. Experiments have found that when water freezes, ice will have a positive charge, while non-frozen water will have a negative charge, so when the updraft in the ice crystal region in the cloud removes the water above the ice particles, it will cause the charge to separate And electrify different cloud regions.
Water drop rupture effect. Use a strong airflow to blow off the water droplets in the air. The larger residual droplets are positively charged and the finer droplets are negatively charged. This is because there are many electrons on the surface of the droplet.
3) Thundercloud discharge mechanism
Due to the uneven distribution of the charges in the clouds, many charge centers are formed, so the electric field strengths between the clouds, between the clouds, and between the clouds and the ground are different. Ground discharge occurs only when the cloud-to-earth field strength is the highest and reaches a certain value. Similarly, when the electric field strength between clouds reaches a certain critical value, an inter-cloud discharge will also occur. In fact, the vast majority of discharges occur between or within clouds.
The mechanism of thundercloud's ground discharge: The cloud with a large amount of charge generates electrostatic induction to the earth, and the earth induces a large number of heterosexual charges, which causes a strong field strength between thundercloud and the earth. At 30kV / cm, a pilot discharge will be generated from the thundercloud to the earth (in some cases, the lightning pilot is emitted from the ground surface upwards). When the leader reaches the ground or meets the ground leader, a strong discharge is generated by charge neutralization to generate a lightning strike. Discharge usually occurs more than once. The first current is very large and the subsequent lightning current is much smaller.
(2) Lightning waveform and main parameters
1) Simulated lightning impulse voltage wave
Simulate the lightning impulse voltage waveform.
The main parameters:
Apparent origin O1 refers to the point where the straight line and the horizontal axis intersect with point A (at 30% of the voltage peak) and point B (at 90% of the voltage peak) on the wavefront.
Time T: refers to the time interval between the two points A and B on the voltage wave.
Wavefront time T1: refers to the time interval from the apparent origin O1 to the point D (= 1.67T).
Half-peak time T2: refers to the time interval from the apparent origin O1 to the voltage peak, and then drops to half of the peak.
2) Simulated lightning impulse current wave
Simulate the lightning impulse current waveform.
The main parameters:
Apparent origin O1: refers to the point where the straight line and the horizontal axis intersect at point C (at 10% of the current peak) and point B (at 90% of the current peak) on the wavefront.
Time T: refers to the time interval between two points C and B on the current wave.
Wavefront time T1: refers to the time interval from the apparent origin O1 to E (= 1.25T).
Half-peak time (wave tail time) T2: refers to the time interval from the apparent origin O1 to the current peak, and then drops to half of the peak value. The longer the wave tail, the greater the energy.
3) Describe the main parameters of lightning
In addition to the parameters mentioned in the waveform diagram, the parameters used to describe lightning include lightning protection areas, thunderstorm days, lightning activity areas, and ground lightning density.
Lightning protection zone: A protected area is classified according to the environment inside and outside the communications bureau (station) building, the communication room and the protected equipment. These protected areas are called lightning protection zones. (LightningProtectionZones, LPZ).
Thunderstorm day: It is used to characterize the frequency of thunder and lightning activity. As long as you hear thunder within one day, it will be recorded as a thunderstorm day.
Lightning activity area: According to the number of annual average thunderstorm days, lightning activity is divided into less mine area, medium mine area, more mine area and strong mine area:
Low minefields are areas where the average annual number of thunderstorm days does not exceed 25 days;
Central minefields are areas where the average annual thunderstorm days are within 25 to 40 days;
The minefield is an area where the average annual number of thunderstorm days is within 40 to 90 days;
Strong minefields are areas where the average annual number of thunderstorm days exceeds 90 days.
Ground Thunderfall Density: The number of times of landfall per square kilometer per year.
(3) Division of lightning protection area
A lightning-prone area is divided into different lightning protection zones (LPZ) from outside to inside according to the environment inside and outside the station building, the communication room and the protected equipment.
Lightning protection zones should be zoned according to the following regulations:
1) LPZOA area
The exposed area, the exterior of the building, and all objects in this area may be subject to direct lightning strikes and conduct all lightning currents. The lightning electromagnetic field in this area is not attenuated.
2) LPZOB area
Objects in this area are unlikely to be subject to direct lightning strikes, but the magnitude of the lightning electromagnetic field in this area is the same as that of the LPZOA area.
3) LPZ1 area
It is impossible for objects in this area to be subjected to direct lightning strikes, and the current flowing through each conductor is smaller than that in the LPZOB area. The lightning electromagnetic field in this area may be attenuated, which depends on shielding measures.
4) Follow-up lightning protection zone (LPZ2, etc.)
When it is necessary to further reduce the lightning current and electromagnetic field, a subsequent lightning protection zone should be introduced, and the requirements of the subsequent lightning protection zone should be selected according to the environment required by the system to be protected.
At the interface of the two lightning protection zones, all metal objects passing through the interface should be equipotentially connected, and shielding measures should be adopted. General principles for dividing minefields.
All power lines and signal lines enter the protected space LPZ1 area from the same place, and are equipotentially connected to the equipotential bonding belt 1 located in the LPZOA area and the LPZ1 area (usually grounded in the incoming room). These lines are in the LPZ1 area and LPZ2 The equipotential bonding strip 2 is then connected to the equipotential bonding strip at the interface of the zone. Connect the shield 1 outside the building to the equipotential bonding strip 1 and the inner shield 2 to the equipotential bonding strip 2. The LPZ2 structured in this way prevents the lightning current from being introduced into this space, nor can it pass through this space.
Lightning protection refers to the prevention of direct lightning or lightning by forming an integrated system that intercepts, guides, and finally releases to the ground.
Meet outdoors
Lightning protection grounding is divided into two concepts. One is lightning protection to prevent damage caused by lightning strikes; the other is grounding, a measure of power consumption that is used to ensure the normal operation of electrical equipment and personal safety.
by
GB 15599-1995 | Lightning Safety Specifications for Petroleum and Petroleum Facilities |
GB 50057-2010 | Code for design of lightning protection of buildings |
GB 50343-2012 | Technical specifications for lightning protection of building electronic information systems (with descriptions) |
GB / T 21431-2008 | Technical specifications for building lightning protection device detection |
GBJ 79-1985 | Code for design of communication grounding for industrial enterprises |
GA 267-2000 | Computer Information System Lightning Electromagnetic Pulse Safety Protection Specification |
JR / T 0026-2006 | Technical Specifications for Lightning Protection of Computer Information System in Banking Industry |
QX | Technical Specifications for Lightning Protection of New Generation Weather Radar Stations |
QX | Technical specifications for lightning protection of automatic weather stations |
QX | Meteorological information system lightning protection electromagnetic pulse specification |
QX | Meteorological station (station) lightning protection technical specifications |
YD 2011-1993 | Lightning protection and grounding design code for microwave stations |
YD 5068-1998 | Design specification for lightning protection and grounding of mobile data communication base stations |
YD / T 5098-2001 | Communication Bureau (Station) Lightning Overvoltage Protection Engineering Design Code |
GA173-2002 | Lightning protection device for computer information system |
QX 10 [1] .1-2002_ | Surge protectors. Part 1: Performance requirements and test methods |
IEC 62305-1-2006 | Lightning protection |
IEC / TR 61400-24-2002 | Wind turbine generator system. Part 24: Lightning protection devices IEC61400-24 |
IEC 60364-5-54 | Electrical installations of the building. Part 5-54: Selection and installation of electrical equipment. Grounding measures, protective conductors and protective jumpers IEC60364-5-54 |
IEC 60099 | lightning arrester |
GB 15599-1995 | Lightning Safety Specifications for Petroleum and Petroleum Facilities |
GB 50057-2010 | Code for lightning protection design of buildings |
GB 50343-2012 | Technical specifications for lightning protection of building electronic information systems (with descriptions) |
GB / T 19271-2003 | Protection against lightning electromagnetic pulses |
GB / T 19663-2005 | Protection against lightning electromagnetic pulses |
GB / T 19663-2005 | Information system lightning protection terminology |
GB / T 19856-2005 | Lightning protection |
GB / T 21431-2008 | Technical specifications for building lightning protection device detection |
GB / T 21714-2008 | Lightning protection |
GB / T 2900.12-2008 | Electrotechnical term lightning arrester, low voltage surge protector and components |
GB / T 7450-1987 | Guidelines for lightning protection of electronic equipment |
GJB 5080-2004 | Lightning protection design and use requirements for military communication facilities |
GJB 1210-1991 | Ground lap and shield design implementation |
GJB 2269-1996 | Technical requirements for lightning protection of the rear ammunition warehouse GB / '1' 3 4 8 2 Lightning strike test methods for electronic equipment GB / T 3 4 8 3 Guidelines for lightning strike test methods for electronic equipment GB 9 0 3 2 Technical requirements for pulsed push-button telephones GB 9 0 3 3 Pulsed push-buttons for telephones Technical requirements for dials GB 9 0 3 4 Technical requirements for dual-tone multi-frequency keypads GB 9 0 3 5 Technical requirements for dual-tone multi-frequency keypads for telephones GB / T 1 5 2 7 9 Technical requirements for automatic telephones |
Lightning protection product certification and product testing agencies:
1. Beijing Lightning Protection Device Testing Center
2. Shanghai Lightning Protection Device Testing Center
3. Institute of Communication Signals, China Academy of Railway Sciences
Lightning protection equipment can be broadly divided into: power lightning protection devices, power protection sockets, antenna feeder protection devices, signal lightning protection devices, lightning protection testing tools, lightning protection devices for measurement and control systems, and ground electrode protection devices. A complete set of lightning protection devices includes lightning receptors, down conductors and grounding devices. The above-mentioned needles, wires, nets, and belts are all just air-termination devices, and lightning arresters are special lightning protection devices. The sum of lightning receptors, down conductors, grounding devices, surge protectors and other connecting conductors.
1. You should stay indoors and close the doors and windows; people working outdoors should hide in the building.
2. It is not suitable to use TV, stereo and other electrical appliances without lightning protection measures or insufficient lightning protection measures, and it is not suitable to use taps.
3.Do not touch the antenna, water pipe,
1) Protected neutral must be insulated. The PE wire connecting the power distribution device and the electric machine should be an insulated multi-strand copper wire with a cross section of not less than 2.5mlIf. The PE wire of the hand-held power tool shall be an insulated multi-strand copper wire with a section of not less than 1.5m.
2) It is strictly forbidden to install switches or fuses on the PE line, it is forbidden to pass the working current, and it is strictly forbidden to disconnect the wire.
3) The color markings of the phase line, N line, and PE line must meet the following requirements: Phase line L1 (A), L2 (B), L3 (C) phase sequence insulation colors are yellow, green, and red; The insulation color is light blue; the insulation color of PE wire is green / yellow. In any case, the above color markings are strictly forbidden to mix and substitute.
4) When the construction site and the external power line share the same power supply system, the grounding and zero protection of the electrical equipment should be consistent with the original system. Part of the equipment should not be connected to zero for protection, and other equipment should be protected for grounding.
5) When the TN system is used for protection connection, the working neutral line (N line) must pass through the total leakage protector, and the protection neutral line (PE line) must be repeatedly grounded by the power input neutral line or the power supply side zero At the line, a local TN-S zero-connection protection system is formed (Figure 2).
6) In the TN zero-connection protection system, no electrical connection can be made between the working neutral line and the protective neutral line of the total leakage protector.
7) In the TN connection zero protection system, the PE neutral line should be laid separately. The repeating ground wire must be connected to the PE wire, and it is strictly prohibited to connect to the N wire.
8) When the primary side is powered by a zero-voltage protection system with a voltage of 50V or more, and the secondary side is a safety isolation transformer with a voltage of 50V or less, the secondary side must not be grounded, and the secondary line should be protected by an insulating tube or rubber protection. Set of soft lines. When a common isolation transformer is used, its secondary side should be grounded, and the exposed conductive part of the transformer that is normally uncharged should be connected to the zero line of the primary circuit protection. The above transformers should also take protective measures against direct contact with live parts. [5]
