Electrical safety of public places is very important both during the operation of the facility as a whole, and for its fire safety in particular. Therefore, educational institutions should be protected from direct lightning strikes and have a good grounding device.
The ZANDZ Technical Center received a request to calculate the necessary equipment for lightning protection and grounding of a college in the Siberian Federal District. Further we will study the offer of the technical specialists.
- object: college;
- dimensions: 29 mx 20 m;
- height: 7.5 m;
- roofing plan;
- soil resistivity taken as 100 Ohm * m.
- grounding device resistance should be not more than 4 ohms;
- сollege lightning protection should be performed using a lightning protection mesh.
Lightning protection and grounding of the college are performed in accordance with:
The object belongs to the "ordinary" in accordance with the IS and to the III category of lightning protection according to the classification of AD.
The set of measures to ensure lightning protection and grounding systems for the college:
1. Lightning protection is carried out with the help of a lightning mesh with the distance between the meshes of 10 m. The mesh is made of steel copper-bonded wire (the tickness of the copper coating is not less than 70 mcm), the diameter of the wire is d8 mm (GL-11149).
2. Copper-bonded steel wire is used as down conductor (thickness of the copper coating not less than 70 mcm), d8mm wire (GL-11149).
4. To connect rolled metal over the length and in the nodes, a universal clamp GL-11551A is used.
6. 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.
7. 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.
8. The rated resistance of the grounding device is 1.99 Ohms.
9. If there are metal reinforce concrete framings, they must be connected to down conductors/ grounding device.
10. Connection to the grounding device is carried out with the help of clamps ZZ-005-064.
Grounding device resistance calculation:
The design resistance of the grounding device is 1,99 Ohm.
Equipment arrangement layout is shown in figure 1
Figure 1 - Location scheme of lightning protection equipment and grounding for the college.
The list of required material is given in Table 1.
Chart 1 - List of equipment and materials.
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