There are no special requirements for lightning protection of office buildings in the AD. But it’s important for designers to remember that the office is the “visiting card” of any large organization, so lightning protection should not spoil its appearance. This nuance was taken into account by the engineers of the ZANDZ Technical Centerwhen they were given the task to calculate lightning protection for one of the office buildings of the Russian Post company. Our experts located lightning rods inside the perimeter of the roof so that they were not too noticeable from the street and did not change the exterior of the building.
Another feature of this project is the low resistance of the grounding device. The office building is large in perimeter, and since the project involves laying a grounding contour along its entire length, the grounding resistance is less than 1 ohm.
We offer you to get familiarized with the project details and calculation example:
Calculation of lightning protection of the "Russian Post" office.
Object: Office building - Russian Post.
Figure 1 - Plan of the object.
Task: Perform calculations of the lightning protection system of the office building of the company “Russian Post”.
Protection of buildings and structures against lightning discharges is ensured by lightning rods. A lightning rod is a device rising above the facility that diverts lightning current into the ground without entering the facility. It consists of a lightning rod which directly takes the lightning discharge upon itself, a down conductor and a ground electrode.
Solutions to ensure the requirements for the lightning protection system of the Russian Post office building:
1. Lightning protection is carried out in accordance with EIC 7th edition., IS 153-34.21.122-2003 "Instructions for lightning protection of buildings, structures and industrial communications" (hereinafter IS) and AD 34.21.122-87 "Instructions for lightning protection of buildings and structures" (hereinafter AD).
2. The object refers to category 3 of lightning protection. System reliability must be not less than 0,9.
3. Lightning protection of the object is carried out using 12 vertical air-terminals masts with the height of 6 m on 3 concrete bases (GL-21125).
4. Connection of down conductors to lightning rods and downdrop to the grounding device;
5. Installation of down conductors is carried out with the help of GL-11711 holder on a flat roof, GL-11704A- on vertical surfaces. Distance between the clamps- from 0.8 up to 1.0 meter;
6. To connect rolled metal over the length a universal clamp GL-11551A is used;
7. All metal structures and communications must be connected to the down conductor with the help of clamps GL-11545A. Stairs, railings are connected with the help of clamp GL-11514;
8. According to IS item 126.96.36.199 we equalize the potentials of the building at the mark of 20 m with the help of a wire 8 mm in diameter; Installation of a grounding device consisting of 4 vertical electrodes of 3 m in length united by a horizontal electrode (a copper-bonded tape of 30x4 mm). The distance from the horizontal electrode to the object should be not less than 1 m, deepening 0.5 - 0.7 meters;
9. Installation of a grounding device consisting of 4 vertical electrodes of 3 m in length united by a horizontal electrode (a copper-bonded tape of 30x4 mm). The distance from the horizontal electrode to the object should be not less than 1 m, deepening 0.5 - 0.7 meters;
10. In case of presence of the existing grounding device, they should be united into one grounding device in accordance with EIC p.1.7.55.
Results of the calculation carried out with the software developed by the JSC "Energy Institute to the name of G.M. Krzhizhanovsky (JSC "ENIN"):
Density of lightning strikes into the ground - 4 strikes / sq. km per year;
The total number of strikes into the system - 0,38 (once in 3 years);
The total number of breakthroughs is 0.038 (once every 26 years);
System reliability — 0.9;
Probability of breakthrough into all the system objects - 0.1.
Grounding device resistance calculation:
The design resistance of the grounding device is 0,64 Ohm..
Figure 2 shows the arrangement of equipment.
Table 1 gives the list of the required equipment and materials.
Figure 2 - Location of equipment for lightning protection of the Russian Post.
Installation example of modular grounding
Table 1 - List of need in materials.