The ZANDZ Technical Center received a request for calculation of lightning protection of an industrial building in the Smolensk region. This facility is designed to store food, which means that the building has a lot of equipment that should work without interruption. Therefore, good grounding and a potential equalization system are necessary so that there are no problems with the operation of electronics
Our experts solved this problem and proposed their solution, which we will consider further.
Initial data for calculation:
-
soil resistivity: 100 Ohm * m;
-
object dimensions: 58 mx 18.5 m;
-
height: 14.5 m + superstructure 17.5 m;
-
power supply 380 V, OTL.
Task:
-
calculate the system of external lightning protection of an industrial building using an air terminal;
-
calculate grounding device
Solution:
Lightning protection and grounding of the industrial building are made in accordance with:
-
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 III category of lightning protection in accordance with AD and to ordinary in accordance with IS.
According to EIC-7, p. 1.7.103. The total speading resistance of the ground electrodes (including natural) of all repeated groundings of the PEN conductor of each overhead line at any time of the year should not exceed 10 ohms at line voltage of 380 V of the three-phase power supply or 220 V of a single-phase power source.
A set of measures to ensure lightning protection and grounding systems for an industrial building:
1. Lightning protection is carried out with the help of a lightning mesh with a 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);
3. Installation of down conductors is carried out with the help of clamp GL-11711 on the roof, GL-11703А -on vertial surfaces. Distance between the clamps- from 0.8 up to 1.0 meter;
To connect rolled metal over the length and in the nodes, a universal clamp GL-11551A is used;
5. 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;
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 calculated value of the resistance of the grounding device is - 1,6 ohms;
11. If there are metal reinforce concrete framings, they must be connected to down conductors/ grounding device;
9. Connection to the grounding device is carried out with the help of clamps ZZ-005-064.
Calculation of the grounding device:
The design resistance of the grounding device is 1,6 Ohms, which is less than the required resistance of 10 Ohm.
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 need to calculate lightning protection system for an industrial building? Send your request to info@zandz.ru.