Project of direct lightning protection for photovoltaic power plants on concrete roof and steel structure roof

I. Project for preventing direct lightning strikes on photovoltaic power plants with concrete roofs

Some basic requirements for lightning protection design of rooftop photovoltaic systems:

For the PV system lightning protection design, the lightning protection level of the project should be determined first, and the materials needed for designing the lightning protection level should be selected, including the lightning arrester, the deflector, etc. According to the particularity of photovoltaic power plant engineering, all rooftop power plants can be attached to the lightning protection system of the main structure of the building, and independent design of independent lightning protection systems is not required. This will not only save time and money, but also make full use of the existing Resources. For concrete structures, most of the buildings have been equipped with a professional lightning protection system during construction. When the concrete structure is used as a lightning protection system, it is generally used as a lightning protection zone or a lightning protection net.


Connection point with main structure lightning protection system

Some of them are the external lightning protection system's down conductor connected to the daughter's wall with a lightning receptor through the bushing. In this case, we can open the casing and directly connect the lightning deflector on the photovoltaic power plant to the parapet wall. On the lead-off line, the thunder-proof steel bar was directly welded to the lightning protection grid without the casing. The overlap length of the welding part should meet the requirements of the specification, and the coating should be removed before the welding part is painted.

In the second case, the original structure will do internal lightning protection, that is, using the reinforcement of the main structure as the deflector. In this case, we can connect the down conductor to the air-termination device. Add a few more air-termination devices and do it on the column of the support system. The lightning receptor is installed as follows:

1. First, fix the bottom plate of the bearing steel plate on the column of the photovoltaic power station support system and weld a help plate;

2, then the lightning rod erected, find straight, find the right after the spot welding, and then be corrected, welded to the other three ribs;

3. Finally, the lead wire will be welded to the bottom plate to remove the anti-rust paint on the medicine brush.

The weakest in the PV power plant system is the frame of the PV module. Considering various factors such as the cost environment, the hot dip galvanized steel is selected as the material used for the lightning protection device. When the connecting rod is made of hot-dip galvanized round steel or steel pipe, its diameter shall meet the following requirements: when the length of the rod is less than 1m, the round steel shall not be less than 12mm, the steel tube shall not be less than 20mm, and the length of 2 rods shall be 1-2m. The round steel should not be less than 16mm, the steel tube should not be less than 25mm; 3 The rod on the top of the independent chimney, the round steel should not be less than 20mm, the steel tube should not be less than 40mm.

The flash terminal of the lightning rod should be made hemispherical, with a minimum bending radius of 4.8 mm and a maximum of 12.7 mm. Overhead flash line and flash network should adopt a hot-dip galvanized steel strand or copper strand with a cross section of no less than 50mm2. In the photovoltaic system, the connecting rod should be connected with the column in the photovoltaic system. The connection between the plates should be a long-lasting electrical penetration, which can be copper-zinc alloy welding, welding, crimping, sewing, screwing or bolting. Taking into account the environmental impact of construction difficulties, the use of welding is better. After doing welding, it is best to do node treatment and do a good job of anti-corrosion and fire prevention.

Second, the steel plant roof photovoltaic power plant direct defense program

2.1 Basic Ideas for Lightning Protection of Rooftop PV Power Plant in Steel Structure Factory

The idea of ​​lightning protection for photovoltaic power plants in steel structure plants is similar to that of concrete. The choice of air-termination devices, the choice of deflectors, and the connection of materials are similar to those of concrete roofs. However, for steel structure roofs, because steel structures are different from concrete for lightning protection, the concrete has an independent lightning protection system, a complete lightning receptor, a down conductor, and a grounding device. However, for the steel structure roof, there is no independent lightning protection system. The entire structure has a good conductor. It can directly introduce the lightning strike into the grounding device.

The building houses do not even have a lightning receptor. Therefore, for steel roofs of photovoltaic power plants, they can be directly connected with the roof of the steel structure and can be connected with the main beams of the steel structure roof to achieve the purpose of lightning protection. We only need to attach the lightning protection system of the photovoltaic power station to the lightning protection system of the concrete structure to achieve the purpose of lightning protection.

In the steel structure lightning protection construction, the lightning protection steel bar can be used after the fixture is completed. After the welding is completed, the system construction of the next photovoltaic bracket is performed. The copper wire is used to connect between the plate and the plate, and the countersunk head tapping screws are used. Hit the board or connect it to the bolts on the panel.

2.2 Steel Structure Rooftop Power Plant Implementation Plan

According to the light steel structure of the building, the use of lightning rods is bulky and inconsistent with the entire building appearance, and the use of metal roof as a lightning receptor, to meet the "Building lightning protection design specifications" (GB50057-2010 version) 4.1. Four of the four requirements are given. For the specification, “the thickness of the sheet metal should not be less than 0.5mm when there is no flammable material under the sheet metal.” The plant envelope structure (roofing) is made of hot dip galvanized steel sheet, and the substrate thickness is 0.53mm (including aluminized zinc layer). Under the roof panel, a glass wool mat 75mm thick was added and wrapped with aluminum foil. The φ1.5 stainless steel wire mesh tray was placed on the upper edge of the purlins.

The connection of the battery board and the structural steel with the copper wire has reached the lightning protection requirements of the rooftop power station, and the joints are well-preserved. Some places in the joint with the steel structure may have paint that will block the conductive properties, so sometimes the skin needs to be stripped off, and the joints at the joints are to be treated after anti-corrosion and rust prevention. Otherwise, the purpose of lightning protection cannot be achieved.

Conclusion:

The basic idea of ​​lightning protection for photovoltaic power plants on the roof of concrete roofs and steel structures is to attach the new system to the original structure and lightning protection system so as to achieve the purpose of lightning protection. The above are some experiences of Lipu Energy Engineering Technology (Shanghai) Co., Ltd. in the design and construction of photovoltaic projects. We hope to share with you.

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