Multifunctional complexes include, in addition to shopping, office and sometimes residential premises. Accordingly, lightning protection and grounding must be performed to organize the electrical safety of the facility.
The ZANDZ Technical Center received a request to calculate a lightning protection system for a multifunctional complex located in Moscow. Let us consider the solution down below.
- object: multifunctional complex in Moscow;
- roof plan with the location of the equipment;
- soil resistivity: 100 Ohm * m.
- calculate external lightning protection system;
- calculation grounding device.
Lightning protection and grounding of the industrial building are made in accordance with:
The object refers to III category of lightning protection in accordance with AD and to "ordinary" in accordance with IS. The reliability of the lightning protection system should be at least 0,9.
A set of measures to ensure the necessary requirements for a lightning protection system and the grounding device of a multifunctional complex is represented by the following solutions:
- The object's lightning protection is made using a lightning protection net made of copper-bonded steel wire d8 mm, with a step of not more than 10 m. The equipment and the exit (platform) are protected by lightning rods-masts with a height of 10 m (ZZ-201-010-3) and lightning rods-masts with a height 14 m (ZZ-201-014-3).
- Steel copper-bonded wire d8 mm (GL-11149) is used as a down conductor (thickness of the copper bonding at least 70 mcm).
- Installation of down conductors is carried out with the help of clamp GL-11711 - on a flat roof, GL-11703A -on vertical surfaces.
- Downdrops are carried out along the perimeter of the object with a step of no more than 25 m. Every 20 m in height and at the base of the object there are down conductor belts being carried out, which equalize the potentials of the down conductor downdrops.
- Distance between the clamps- from 0.8 up to 1.0 meter.
- A universal clamp GL-11551A is used for connecting the mill products along the length and in the nods.
- All metal elements, placed on the roof must be connected to the down conductor with the help of clamps GL-11545A and GL-11514N.
- Copper-bonded steel electrodes 3 m long are used in places of downdrops as a vertical ground electrodes. 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. Deepening of the tape 0,5-0,7 m.
- 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.
- If there are metal reinforce concrete framings, they must be connected to down conductors/ grounding device.
- Connection to the grounding device is carried out with the help of clamps ZZ-005-064.
Results of calculations 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 is 1,02 (once a year);
The total number of breakthroughs is 0.087 (once every 11 years);
The reliability of the system is 0.915;
Probability of a breakthrough into all the system objects - 0.085.
The resistance calculation of the grounding device:
Vertical electrode resistance:
where ρэкв equivalent soil resistivity - 100 Ohm*m;
L - vertical electrode length - 3 m;
d - vertical electrode diameter - 0.014 m;
T - deepening - the distance from the ground surface to the ground electrode system - 2 m;
where t is the deepening of the electrode top - 0,5 m
Horizontal electrode resistance:
where ρ - equivalent soil resistivity - 100 Ohm*m;
b - width of the horizontal electrode - 0.03 m;
h - horizontal electrode laying depth -0.5 m;
Lгор horizontal electrode length - 155 m.
Impedance of the grounding device:
where n number of kits, vertical ground electrodes -9 pc., horizontal ground electrode - 1 pc. ;
Kисп - utilization ratio, 0.69
The design resistance of the grounding device is 1,59 ohm.
Location of equipment is shown in figure 1.
Figure 1 - Location of equipment.
The list of required material is given in Table 1.
Table 1 - List of materials needs.
|№||Product item||Name||Quantity, pcs.||Weight, kg.||Note|
|1.||ZZ-201-014-3||ZANDZ vertical air terminal 14 m (galvanized steel; for installation on a flat roof)||5|
|2.||ZZ-201-010-3||ZANDZ Air-terminal mast vertical 10 m with a set of 3 fastenings to the wall (stainless steel)||3|
|3.||ZZ-202-002||ZANDZ Clamp to the lightning rod D42 mm for down conductors (stainless steel)||3||0,43|
|4.||GL-11149-50||GALMAR Copper-bonded wire (D 8mm / S 50 mm²; coil of 50 meters)||28||0,41||В бухтах. Масса за метр.|
|5.||GL-11545A||GALMAR Clamp on the gutter for a down conductor (painted galvanized steel)||70||0,112|
|6.||GL-11551A||GALMAR Clamp for connecting down conductors (painted galvanized steel)||350||0,07|
|7.||GL-11711||GALMAR Clamp on a flat roof for the down conductor (plastic, concrete)||350||1 - 1,2|
|8.||GL-11703A||GALMAR Clamp to the facade for down conductor with its elevation above the clamp to 15 mm (painted galvanized steel)||1800||0,02|
|9.||GL-11514N||GALMAR Clamp-bridge on a gutter for down conductor (tinned copper)||20||0,076|
|10.||GL-11075-50||GALMAR Copper-bonded tape (30 * 4 mm / S 120 mm²; coil 50 meters)||4||0,98||В бухтах. Масса за метр.|
|11.||ZZ-001-065||ZANDZ Copper-bonded threaded grounding rod (D14; 1.5 m)||18||2,00|
|12.||ZZ-002-061||ZANDZ Threaded coupler||10||0,08|
|13.||ZZ-003-061||ZANDZ Starting tip||9||0,07|
|14.||ZZ-004-060||ZANDZ Driving head for jackhammer||4||0,09|
|15.||ZZ-005-064||ZANDZ Clamp for connecting conductors (up to 40 mm)||23||0,16|
|16.||ZZ-006-000||ZANDZ Conductive grease||2||0,10|
|17.||ZZ-007-030||ZANDZ Waterproof tape||6||0,40|
|18.||ZZ-008-000||ZANDZ Header for a jackhammer (SDS max)||1||0,50|
Do you have any questions about lightning protection and grounding of the multifunctional complex? Contact the ZANDZ Technical Center!