How to make the solar panels earthing and lightning protection on the roofing?

We have already presented the earthing and lightning protection design made by our engineers for the solar power plant. Recently, ZANDZ has received one more request for calculation of the earthing and lightning protection systems for a solar energy facility. And this time the customer decided to install the solar panels not on the soil, but on a building roofing. Let us consider what ZANDZ's experts succeeded for the object like this one:

Example of the solar panels lightning protection calculation:

Object: Solar power plant on the building roofing.

Figure 1 - Object dimensions.

Task: Make calculations of the roofing solar panels earthing and lightning protection system.

Protection of the buildings and structures against lightning discharge is provided by using the lightning arresters. The lightning arrester is a device which is elevated over an object and through which the lightning current goes into the ground bypassing the protected object. It consists of an air terminal which is specially designated to arrest the lightning discharge, a conductor and a ground terminal.

The set of arrangements ensuring compliance with the lightning protection requirements is based on the following solutions:

1. The lightning protection is made in accordance with Electrical Installations Code (EIC), Rev. 7, SO 153-34.21.122-2003 "Guidelines for making the lightning protection of buildings, structures and industrial infrastructure" (hereinafter - SO) and RD 34.21.122-87 "Guidelines for making the lightning protection of buildings and structures" (hereinafter - RD).
2. The object is classified as per the lightning protection category 3. The system reliability shall be at least 0.9.
3. The object lightning protection is made by using 3 vertical two-meter lightning arresters on the crest (GL-11521SS).
4. The conductors are laid by using clamps GL-11564A on the crest, GL-11747A for horizontal surfaces, GL-11545A for rain gutter and GL-11514 for the rain pipe. The clamp spacing is 0.8 to 1.0 m.
5. Universal clamp GL-11551A is used for securing rolled metal along the distance, as well as in the grid nodes.
6. All metallic elements located on the roofing shall be connected to the lightning protection grid by using clamps GL-11545A, stairs and handrails are connected by using clamp GL-11514.
7. Existing ground terminal is used as the earthing hardware.

 

Results of the calculations performed by using the software developed by OAO G.M. Krzhizhanovskiy Energy Institute (OAO ENIN):
Intensity of lightning discharge into the ground is 6 strikes/square km/year;
Total number of strikes into the system is 0.064 (times per 16 years);
Total number of blowouts is 0.0045 (times per 222 years);
System reliability is 0.93;
Probability of blowout into all objects of the system is 0.070.

 

Figure 2 shows hardware layout.
Table 1 includes the list of required hardware and materials.

 Заземлено и защищено Earthed and protected

Присоеденить токоотводы к существующему заземляющему устройству - Connect conductors to existing ground terminal

Условные обозначения - Reference designation

Молниеприёмник - мачта коньковый, высотой 2 м - Lightning mast, crest, height of 2m

Вертикальное возвышение токоотвода на высоту 1м - Conductor elevated vertically to 1 m

Проволока омеднённая стальная диаметром 8 мм - Copper-plated steel wire, diameter of 8 mm

Опуск токоотвода - Conductor embedment

Зажим для соединения токоотводов - Conductors coupling

Зажим на водосточный желоб для токоотвода - Conductor rain gutter clamp

Зажим хомут на водосточную трубу для токоотвода - Conductor rain pipe clamp

 

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