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.
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:
- object: electromechanical plant;
- object plan;
- it is necessary to protect the space above the pipes with gas emissions in accordance with AD 34.21.122-87, p. 2.6, 2.11 (R = 5 m, H = 2.5 m).
- soil resistivity - 100 Ohm * m.
Lightning protection and grounding of a depot are performed in accordance with:
- EIC "ELECTRICAL INSTALLATION CODE" , 7th edition, hereinafter EIC-7;
- IS 153-34.21.122-2003 "INSTRUCTIONS FOR LIGHTNING PROTECTION OF BUILDINGS, STRUCTURES AND INDUSTRIAL COMMUNICATONS", hereinafter IS;
- AD 34.21.122-87 "INSTRUCTION ON LIGHTNING PROTECTION OF BUILDINGS AND STRUCTURES", hereinafter AD.
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
The list of required equipment and materials is given in table.1.
Table 1 - List of required equipment and materials.
Do you have questions or you need to calculate lightning protection systen for a factory? Send your request to email@example.com.