There are four main types of lightning strikes:
1. Direct lightning
Direct lightning contains great energy, and the lightning current with a peak voltage of up to 5000kv enters the ground, which has great destructive power. Will cause the following three effects:
(1) The huge rich current flows to the ground within a few microseconds, causing the ground potential to rise quickly, causing a counterattack accident and endangering the safety of people and equipment.
(2) The lightning current generates powerful electromagnetic waves, which induce extremely high pulse voltages on the power line and signal line.
(3) The lightning current flowing through electrical equipment generates extremely high heat, causing fire or explosion accidents.
2. Conductive thunder
The lightning strikes the line at a distance or the extremely high voltage generated by electromagnetic induction is transmitted from the outdoor power line and communication line to the indoor electrical equipment in the building.
3. Induction mine
Frequent discharges between clouds produce strong electromagnetic waves, causing common mode and differential mode interference, which affects the operation of electrical equipment.
4. Switch overvoltage
The inductive and capacitive loads in the power supply system are turned on or off, ground short-circuit, power line short-circuit, etc., can generate high-voltage pulses on the power line, the pulse voltage can reach 3 to 5 times the normal voltage, which can seriously damage the equipment . The damage effect is similar to that of a lightning strike.
The most effective way to prevent street lights from being damaged by lightning:
1. Combination of external lightning protection and internal lightning protection
The exterior of the general LED street light is made of conductive material, which is equivalent to a lightning rod. In the design, down conductors and ground nets must be installed. These systems constitute an external lightning protection system. The system can avoid fire and personal safety accidents caused by direct lightning strikes of LED street lights. The internal lightning protection system refers to the protection of the equipment inside the street lamp by grounding and setting voltage protection. The system can prevent the intrusion of induced lightning and other forms of overvoltage, which can cause damage to the power supply, which cannot be guaranteed by external lightning protection systems. The two are complementary to each other. The internal lightning protection system must be connected to the external lightning protection system or set with overvoltage protectors on many components such as the housing, cables entering and leaving the protected area, and metal pipes, and equipotential connection is performed.
2. Lightning protection equipotential connection
In order to completely eliminate the destructive potential difference caused by lightning, power lines, signal lines, metal pipes, etc. must be equipotentially connected with overvoltage protectors, and local equipotential connections must be made at the interface of each inner protection zone. The local equipotential junctions should be connected to each other, and finally connected to the main equipotential place.
3. Set up lightning protection zone
In addition to power supply equipment, LED street lights will also be equipped with some communication equipment to control the switch and brightness of the street lights. These equipment and power supplies need to be placed in the lightning protection area, and the protection area is directly shielded by the shell. The electromagnetic field here is much weaker.
4. High-quality protection equipment-lightning protection module and overvoltage protection module
The function of the lightning arrester is to connect the protected system to the equipotential system within the shortest time (nanosecond level), so that the equipment ports are equipotential. At the same time, the huge pulse energy generated by the lightning strike in the circuit is released to the ground through the short-circuit line, which reduces the potential difference between the equipment interfaces and protects the equipment.
