LED street light lightning surge protection technology and related standards

The main customers of street lamps are government units, not ordinary consumers, and thus are a relatively special and relatively closed industry. The street lamp has undergone a long process of development from the initial sodium lamp, mercury lamp to the current LED lamp. At the same time, some technical problems have been encountered in this development process.

Today, LED street lamps have been in China for about ten years, including power supply, power supply, heat dissipation technology , optical technology, etc., each year has new breakthroughs, and some basic technologies have not been resolved in China, LED street lights The lightning protection problem is one of the problems to be solved.

The necessity of lightning protection for LED street lights

Lightning strikes are electrostatic discharges that typically carry millions of volts from the clouds to the ground or to another cloud. During transmission, lightning generates electromagnetic fields in the air, inducing thousands of volts (ie, surges) to the power line and generating induced currents that travel hundreds of miles away. These indirect attacks typically occur in outdoor exposed wires, such as street lights. Equipment such as traffic lights and base stations transmit surges. The surge protection module directly faces the surge interference from the power line at the front end of the circuit. It transfers or absorbs surge energy, minimizing the threat of surges to other working circuits, such as AC/DC power units in LED lighting fixtures.

For LED street lights, lightning generates an induced surge on the power line. This surge of energy creates a surge on the wire, that is, a surge wave. The surge is transmitted through such induction. The outside world has a surge. The wave will create a tip on the sine wave in the 220V transmission line. When the tip enters the street light, it will damage the LED street light circuit.

Street lamps have been around for many years. Why do you need to find lightning protection for street lights now? In fact, the high-pressure sodium lamps and traditional mercury lamps used in the past are designed with high-pressure bulbs, which have the effect of lightning protection. In recent years, LED lamps have become more and more popular. LED lamps need to have a small supply voltage. Usually, the power supply is used to convert AC power into DC power. This makes the LED street lamp itself have no lightning protection, so it needs to be designed for street lamps. Lightning protection module.

The importance of streetlight lightning protection is determined by the concept of payback period. Since the LED street lamp is about twice as expensive as the traditional street lamp, the government has a large investment amount at the beginning of the purchase. Therefore, it is necessary to gradually save the cost by saving electricity expenditure during the operation. Therefore, the life of the LED lamp is very important. If the LED light has not earned back the cost and it is broken during the investment recovery period, it will cost money to repair it. The labor cost for maintenance is twice as expensive as the installation. Therefore, in the LED era, to achieve the effect of saving power and saving money, it is necessary to ensure that its life expectancy can reach your expectations, that is, the product shelf life is long. To achieve cost savings and ensure that street lights are not damaged during the investment recovery period, reliability needs to be increased. This requires a lightning protection module for the LED streetlight to maximize the economy.

Energy-saving street lamps have been used in China. The defined street lamp specifications are usually visible indicators such as brightness, illumination angle, light color, power consumption, etc., and lightning-proof indicators are often ignored. Not only the United States and Europe, but also in countries with high mines, such as Malaysia and India, have long established standards for requiring local streetlights to pass a set lightning protection test. Because only the coastal cities such as Hainan and Zhujiang are more serious in the country, most of the inland areas are much better. Therefore, the relevant standards have not been introduced so far.

US three-level lightning protection standard

In the US National Standards released in 2015, three levels of lightning protection standards have been introduced, as shown in Table 1. The reason is that the three grades are due to the fact that the tribes of the East and West tribes in the United States are quite different. The high mines can reach 30 to 40 times, while the low mines have only one or two times. Therefore, three levels are standard. 6kV, 10kV and 20kV. This is also a flexibility for luminaire manufacturers and local governments. Local governments can decide to use the corresponding standards according to actual conditions.

Domestic relevant standards have yet to be worked out

Domestic communication base stations have similar standards. As early as ten or twenty years ago, when mobile phones were about to become popular, base station lightning protection already had relevant national standards. Since the base station is mainly installed on the roof or the tower, the impact of the lightning strike on the base station will be large. Due to the large difference between the north and the south of China, there are also large differences in the inland environment along the coast. Moreover, the street lamps are basically managed by local governments, and the specifications, bidding, supervision, maintenance, etc. are still in place. The standard was introduced.

With the obvious demand in recent years, the national standards for lightning protection of LED street lamps have been under review in 2017 and 2018, as shown in Table 2. With reference to the national standards of countries all over the world, if the drive power module only meets the fourth level (line-line 2kV, line-ground 4kV), it will not be enough to cope with the lightning surge threat that outdoor lighting may face. It is recommended to adopt a higher street light. Lightning protection level and lightning protection module.

Lightning protection module

Although the lightning protection module itself can provide lightning protection for LED lights, it also has its own risks. When the lightning protection module ages, it will internally react to overheating and even cause fire. That is to say, the lightning protection module will have a risk of fire at the last moment, as shown in Figure 2, which is the device after the aging of the lightning protection module. Therefore, the security of the lightning protection module is an important concept. Installing the lightning protection module is a concept. Installing a safe lightning protection module is a further concept and challenge.

The lightning protection module of Lite has a varistor (voltage-sensitive resistor) to realize the lightning protection function. When the surge voltage rises, the resistance of the varistor decreases, and the surge current is discharged into the power grid, thereby avoiding large current. Flow through the drive. The principle is that no matter which line of the L/N/G three lines is affected by lightning strikes, it can be discharged from another line. The related products of Lite LSP05 & LSP10 are shown in Figure 3.

Lite's lightning protection module can be verified by two safety agencies, UL and European IEC/EN, to ensure the safety of their lightning protection module. In addition to protecting the lamps from lightning strikes, the module itself Safety is also ensured by safety regulations. This provides a large lightning protection capability in a small volume, providing a safe and reliable lightning protection module to the street lamp industry at a reasonable cost, size and price.

in conclusion

With the advent of the intelligent era, intelligent street lights have entered the practical application scenarios. Intelligent street lights represent street lights that enable street lights to be turned on and off at the remote IoT, and can adjust the color and brightness of street lights. Relatively speaking, smart devices have more and more functions, and reliability has to be improved. Security issues are crucial. For lightning protection, lightning protection and safety functions should be met at the same time.