В The ZANDZ Technical Center eceived a request for the calculation of an external lightning protection system for a closed-type special equipment parking lot in the Kurgan region. Let us consider the solution that was proposed by our engineers.
- soil resistivity -100 Ohm * m;
- dimensions: 36x12x6.4 m.
- calculate external lightning protection system;
- calculate a grounding device with the resistance of not more than 4 Ohm.
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 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:
1. Lightning protection of the object is made using lightning rods with the height of 5 m (ZZ-201-005) that are attached, and with lightning rods with a height of 1.5 m (GL-21134) that are attached along the edges of the roof..
2. Steel copper-bonded wire d8 mm (GL-11149) is used as a down conductor (thickness of the copper bonding at least 70 mcm).
3. Installation of down conductors is carried out with the help of GL-11747A clamp on the roof, GL-11703A - on vertical surfaces. Distance between the clamps- from 0.8 up to 1.0 meter.
4. A universal clamp GL-11551A is used for connecting the mill products along the length and in the nods.
5. The metal structure of the object is connected to the grounding device around the perimeter, at least after 20-25 m.
6. Copper-bonded steel electrodes 3 m long are used in places of downdrops as 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.
8. 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.
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 0,02 (once in 50 years);
The total number of breakthroughs is 0.0021 (every 476 years);
The reliability of the system is 0.9;
Probability of breakthrough into all the system objects - 0.1.
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 - the length of the horizontal electrode is 107 m.
Impedance of the grounding device:
where n number of kits, vertical ground electrodes -5 pc., horizontal ground electrode - 1 pc. ;
Kисп - utilization ratio, 0.81.
The design resistance of the grounding device is 2 ohm.
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.||Mass, kg||Note|
|1.||GL-21134||GALMAR Air terminal mast (1.5 meters; for vertical surfaces, galvanized steel)||4|
|2.||ZZ-201-005||ZANDZ Vertical air-terminal -mast 5 m (stainless steel)||2|
|3.||ZZ-203-001||ZANDZ Fastening for lightning rod to the wall (stainless steel)||2|
|4.||ZZ-202-002||ZANDZ Clamp to the lightning rod D42 mm for down conductors (stainless steel)||2|
|5.||GL-11149-50||GALMAR Copper-bonded wire (D 8mm / S 50 mm²; coil of 50 meters)||2||0,41||Вес за метр|
|6.||GL-11551A||GALMAR Clamp for connecting down conductors (painted galvanized steel)||10||0,07|
|7.||GL-11747A||GALMAR Clamp for the roof covered with metal profiles / corrugated sheets, for down conductor (painted galvanized steel)||100||0,05|
|8.||GL-11703A||GALMAR Clamp to the facade for down conductor with its elevation above the clamp to 15 mm (painted galvanized steel)||16||0,02|
|9.||GL-11075-50||GALMAR Copper-bonded tape (30 * 4 mm / S 120 mm²; coil 50 meters)||2||0,98||Вес за метр|
|10.||GL-11075-20||GALMAR copper-plated tape (30 * 4 mm / S 120 mm²; coil of 20 meters)||1||0,98||Вес за метр|
|11.||ZZ-001-065||ZANDZ Copper-bonded threaded grounding rod (D14; 1.5 m)||10||2,00|
|12.||ZZ-002-061||ZANDZ Threaded coupler||6||0,08|
|13.||ZZ-003-061||ZANDZ Starting tip||5||0,07|
|14.||ZZ-004-060||ZANDZ Driving head for jackhammer||2||0,09|
|15.||ZZ-005-064||ZANDZ Clamp for connecting conductors (up to 40 mm)||14||0,16|
|16.||ZZ-006-000||ZANDZ Conductive grease||1||0,10|
|17.||ZZ-007-030||ZANDZ Waterproof tape||5||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 special equipment parking lot? Contact the ZANDZ Technical Center!