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CALCULATION EXAMPLE OF LIGHTNING PROTECTION FOR A PLANT

In any production, they carefully approach electrical safety systems, in particular, grounding and lightning protection, because the consequences of a lightning strike can be very disastrous.

plant lightning protection

The ZANDZ Technical Center received a request for the calculation of grounding and lightning protection systems for the plant. Our experts prepared the following solution:

 

Initial data:

 

Task:

Solution:

Lightning protection and grounding of a depot are performed in accordance with:


 

The object refers to category II of lightning protection. System reliability must be not less than 0,95.

 

A set of measures for the implementation of lightning protection and grounding systems of the plant:

1. Lightning protection of the plant is made in the form of a lightning protection mesh with a pitch of not more than 6x6 m, using copper-bonded wire (copper coating thickness of at least 70 μm) d8 mm.

2. Lightning protection of communications, mines, pipes rising above the roof is made using lightning rods on 3 concrete bases 8 m high (GL-21129). Connection to down conductors is carried out using the clamp included in the air terminal kit.

3. Copper-bonded steel wire is used as down conductor (thickness of the copper coating not less than 70 mcm), d8mm wire (GL-11149). Down conductors are dropped down every 15 m along the perimeter of the facility, according to IS 153-34.21.122-2003 , table 3.3.

4. Installation of down conductors is carried out with the help of clamp GL-11711 on a flat roof, GL-11704А - on vertical surfaces and parapets. Distance between the clamps- from 0.8 up to 1.0 meter.

5. To connect rolled metal over the length and in the nodes, a universal clamp GL-11551A is GL-11551A used.

6. All metal elements, placed on the roof must be connected to the down conductor with the help of clamps GL-11545А. Stairs and hand railings are connected with the help of a clamp-bridge GL-11514.

7. Copper-bonded steel electrodes 3 m long are used in places of downdrops as a vertical ground electrode. Copper-bonded steel tape with the cross-section of 30x4 mm uniting all vertical electrodes is used as a horizontal ground electrode. The distance to the object foundation- not less than 1 m. Burial depth of the tape 0,5-0,7 m.

8. In accordance with the EIC-7 ed., p.1.7.55 - Grounding devices for protective grounding of electrical installations of buildings and structures and lightning protection of the 2nd and 3rd categories of these buildings and structures, as a rule, should be common.

9. The calculated value of the grounding device resistance is - 1,01 Ohms.

10. If there are metal reinforce concrete framings, they must be connected to down conductors/ grounding device.

11. Connection to the grounding device is carried out with the help of clamps ZZ-005-064.

 

Results of the calculation carried out with the software developed by the OJSC "Energy Institute to the name of G.M. Krzhizhanovsky (OJSC "ENIN"):

  • the density of lightning strikes into the ground - 4 strikes / sq. km per year;
  • the total number of strikes into the system in: 0.13 (once in 8 years).
  • the total number of breakthroughs (strikes directly into the object by-passing lightning rods) - 0.0063 (once in 159 years).
  • system reliability - 0.953.

     

 

Grounding device resistance calculation:

 

The design resistance of the grounding device is 1,01 1,01 ohms, which is less than the required value of 4 ohms.

 

The layout of the equipment is shown in Fig.1

Figure 1 - lightning protection and grounding system

Figure 1 - lightning protection and grounding system

 

The list of required equipment and materials is given in table.1.

 

Table 1 - List of required equipment and materials.

Item. Designation Name Qty. Weight, kg Note
1. GL-21129 GALMAR Air terminal mast (8.0 m on 3 concrete foundations; two-stage catenary wire support; galvanized steel) 8 135  
2. GL-11149-50 GALMAR Copper-bonded wire (D 8mm / S 50 mm²; coil of 50 meters) 32 0,41 In meters
3. GL-11545A GALMAR Clamp on the gutter for a down conductor (painted galvanized steel) 40 0,112  
4. GL-11551A GALMAR Clamp for connecting down conductors (painted galvanized steel) 220 0,07  
5. GL-11711 GALMAR Clamp on a flat roof for the down conductor (plastic, concrete) 1050 1 - 1,2  
6. GL-11704A GALMAR Clamp for fixing down conductor (painted galvanized steel) 550 0,02  
7. GL-11514 GALMAR Clamp-bridge on a gutter for down conductor (tinned copper) 20 0,076  
8. GL-11075-50 GALMAR Copper-bonded tape (30 * 4 mm / S 120 mm²; coil of 50 meters) 6 0,98 In meters
9. ZZ-001-065 ZANDZ Copper-bonded threaded grounding rod (D14; 1.5 m) 34 2,00  
10. ZZ-002-061 ZANDZ Threaded coupler 18 0,08  
11. ZZ-003-061 ZANDZ Starting tip 17 0,07  
12. ZZ-004-060 ZANDZ Driving head for a jackhammer 7 0,09  
13. ZZ-005-064 ZANDZ Clamp for connecting conductor (up to 40 mm) 42 0,312  
14. ZZ-006-000 ZANDZ Conductive grease 2 0,10  
15. ZZ-007-030 ZANDZ Waterproof tape 11 0,40  
16. ZZ-008-000 ZANDZ Header for a jackhammer (SDS max) 1 0,50  

 

Do you have questions or you need to calculate lightning protection systen for a factory? Send your request to info@zandz.ru.

 

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