ZANDZ Technical Center has received a request to calculate the lightning protection system for the animal shelter. One of the facility was a cat unit. We will consider the example calculation.
Initial data:
-
soil resistivity 100 Ohm*m;
-
facility dimensions: 17.2 х 18 х 5.88 m.
Task:
-
calculate the lightning protection system;
-
calculate the grounding arrangement.
Solution:
Lightning protection and grounding of the building are made in accordance with:
-
SO 153 34.21.122 2003 "INSTRUCTIONS FOR MOUNTING LIGHTING PROTECTIONS OF BUILDINGS, STRUCTURES AND INDUSTRIAL COMMUNICATIONS", hereinafter referred to as SO;
-
RD 34.21.122 87 "INSTRUCTIONS FOR MOUNTING LIGHTING PROTECTION OF BUILDINGS AND STRUCTURES", hereinafter RD.
The facility is “conventional” from the viewpoint of SO and refers to category III of the lightning protection according to RD.
A set of measures to meet the necessary requirements to the lightning protection system and to the grounding arrangement of the cat unit includes the following solutions:
1. The facility lightning protection is performed using the lightning grid made of a steel copper-plated wire d8 mm. Grid step is at least 10 m.
2. Metal caps should be provided on all air shafts that will function as natural lightning arresters.
3. A steel copper-plated wire d8 mm (GL-11075) is used as a lightning arrester.
4. Current collectors are connected by horizontal bands near the ground and each 20 m along the building's height according to SO 153-34.21.122-2003, item 3.2.2.3.
5. Installation of current collectors is performed using clamps GL-11747A on the roof, using GL-11703A on ramparts and vertical surfaces. The clamp installation interval is 0.8 to 1.0 m.
6. The multifunctional GL 11551A clamp is used to connect the rolled products over the length and in assemblies.
7. All metal elements located on the roof must be connected to the down conductor using GL-11545A clamps. Stairs, railings, are attached using the GL 11514N ring clamp
8. Galvanized steel electrodes 3 m long in the places of main conductors downdrops are used as vertical ground electrodes. The copper-plated steel strip with a cross-section of 30 x 4 mm, combining all vertical electrodes, is used as a horizontal ground electrode. The distance to the facility foundation is at least 1 m. Strip deepening is 0.5 to 0.7 m.
9. According to EIC-7 issue, item 1.7.55, Grounding devices for protective grounding of electrical installations for buildings and structures and the 2nd and 3rd categories lightning protection of these buildings and structures usually should be common.
10. The design resistance of the grounding arrangement is 2.75 ohms.
11. If there are reinforced concrete structures, they should be connected to current collectors/grounding device.
12. Connection to current collectors is performed with the interval not more than 20-25 m using clamps ZZ-005-064.
Ground terminal resistance calculation:
Vertical electrode resistance:
where ρρeq is soil equivalent resistivity, 100 ohm·m;
L – is vertical electrode length, 3 m;
d – is diameter of the vertical electrode, 0.014 m;
T – deepening - is the distance from the ground surface to the ground electrode, 2 m;
where t – is deepening of the top of the electrode, 0.5 m
Horizontal electrode resistance:
where ρ – is soil resistivity, 100 ohm·m;
b - is horizontal electrode width, 0.03 m;
h - is horizontal electrode depth, 0.7 m;
Lhor – is horizontal electrode length, 78 m.
Electrical impedance of the grounding arrangement:
where n is number of sets, vertical grounding arrangements 4 pcs, horizontal grounding arrangement 1 pc;
Kutil – is utilization rate, 0.75.
The design resistance of the grounding arrangement is 2,75 ohm..
Figure 1. Equipment layout.
The list of necessary materials is given in Table 1.
Table 1. List of needed materials.
|
№ |
Part number |
Name |
Quantity, pcs. |
Unit weight, kg |
Note |
|
LIGHTNING PROTECTION: |
|||||
|
1. |
GL-11149-50 |
Copper-plated wire GALMAR (D 8 mm / S 50 mm²; 50-meter coil) |
3 |
0,41 |
In meters |
|
2. |
GL-11545A |
GALMAR Main conductor rain water gutter terminal (painted galvanized steel) |
4 |
0,112 |
|
|
3. |
GL-11551A |
GALMAR Clamp for connecting current collectors (painted galvanized steel) |
25 |
0,07 |
|
|
4. |
GL-11747A |
GALMAR Roof clamp coated with metal profile, for current collectors (painted galvanized steel) |
150 |
0,02 |
|
|
5. |
GL-11703A |
Conductor front terminal GALMAR providing 15mm elevation of the main conductor over the terminal (painted galvanized steel) |
20 |
0,02 |
|
|
6. |
GL-11514N |
GALMAR Ring clamp on rainwater pipe for current collector |
4 |
0,076 |
|
|
GROUNDING ARRANGEMENT: |
|||||
|
7. |
GL-11075-50 |
Copper-clad strip GALMAR (30*4 mm / S 120 mm²; 50-meter strip bundle) |
2 |
0,98 |
In meters |
|
8. |
ZZ-001-065 |
ZANDZ Copper-plated threaded grounding rod (D14; 1,5 m) |
8 |
2,00 |
|
|
9. |
ZZ-002-061 |
ZANDZ Threaded coupling |
5 |
0,08 |
|
|
10. |
ZZ-003-061 |
ZANDZ Termination |
4 |
0,07 |
|
|
11. |
ZZ-004-060 |
ZANDZ guide head for jackhammer attachment |
2 |
0,09 |
|
|
12. |
ZZ-005-064 |
ZANDZ Conductor connection terminal (up to 40 mm) |
11 |
0,312 |
|
|
13. |
ZZ-006-000 |
ZANDZ conductive grease |
1 |
0,15 |
|
|
14. |
ZZ-007-030 |
ZANDZ Waterproofing tape |
4 |
0,40 |
|
|
15. |
ZZ-008-000 |
ZANDZ Attachment to the hammer (SDS max) |
1 |
0,50 |
|
Do you have questions regarding lightning protection and grounding of the cat unit? Please, contact the ZANDZ Technical Center!
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