When the equipment is installed on the roof, it is affected to lightning strike; therefore, you have to provide the lightning protection system. The ZANDZ Technical Center has received a request to calculate the lightning protection system for the ammonia compressor workshop for the meat processing plant located in the European part of Russia.
Let's consider the solution offered by our specialists.
Initial data:
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facility: compressor workshop,
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dimensions: 12 x 5 x 6.5 m;
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equipment height on the roof: 5.3 m;
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soil resistivity: 100 Ohm*m.
Task:
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calculate the lightning protection system;
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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 to as RD.
The facility is “conventional” from the viewpoint of SO and is classified as Category III of the lightning protection according to RD. The system reliability shall be at least 0.9.
A set of measures to provide the necessary requirements to the lightning protection system and to the grounding arrangement for the compressor workshop includes the following solutions:
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The lightning protection of the facility is made using lightning rod (ZZ-201-008-3) attached to the facade.
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A copper-plated steel wire (copper coating thickness is at least 70 μm), d8 mm (GL-11149) is used as a current collector.
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Current collectors are installed using clamps GL-11711 on the roof and GL-11703A on vertical surfaces. The clamp installation spacing is 0.8 to 1.0 m.
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The multipurpose GL 11551A clamp is used to connect the rolled products over the length and in assemblies.
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All metal elements located on the roof should be connected to current collectors.
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Copper-plated steel electrodes 3 m long in the locations of the current collector 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.
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According to EIC-7 issue, par.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, as a rule, shall be common.
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If there are concrete-steel constructions, they shall be connected to down conductors/grounding device.
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Connection to the grounding arrangement is made through the terminals ZZ-005-064.
Results of the calculations performed by using the software developed by OAO Krzhizhanovsky Energy Institute (OAO ENIN):
The occurrence of lightning strokes into the ground is 4 strokes/sq. km per year
The total number of strikes into the system is 0.03 (once every 33 years).
The total number of breakouts into the system is 0.0029 (once every 345 years).
System reliability is 0.903;
The probability of breakout into all facilities of the system is 0.097.
Ground terminal resistance calculation:
Vertical electrode resistance:
Ом - Ohm
Верт - Vert
where ρρeq – is equivalent soil resistivity, 100 Ohm·m;
L – is vertical electrode length, 3 m;
d – is diameter of the vertical electrode, 0.014 m;
T – is deepening, i.e. the distance from the ground surface to the ground electrode, 2 m;
м - m
where t – is deepening of the electrode top, 0.5 m.
Horizontal electrode resistance:
Ом - Ohm
Гор - Hor
where ρ – is soil resistivity, 100 Ohm·m;
b - is horizontal electrode width, 0.03 m;
h - is horizontal electrode depth, 0.5 m;
Lгор – is horizontal electrode length, 12 m.
Electrical impedance of the grounding arrangement:
where n – is a number of sets, vertical grounding arrangements - 2 pcs, horizontal grounding arrangement - 1 pc;
Kutil – is utilization rate, 0.81.
The rated resistance of the grounding arrangement is 8,98 Ohm.
The location of the equipment is shown in Figure 1.
Условные обозначения - Key Symbols
- молниеприемник-мачта высотой 8 м - 8 m lightning rod
- полоса стальная оцинкованная сечением 30х4 мм - steel zinc-plated bar with cross-section 30 x 4 mm
- зажим для подключения проводника - clamp for connecting conductor
- вертикальный заземлитель длиной 3 м - 3 m vertical grounding electrode
- проволока стальная омедненная d8 мм - steel copper-plated wire d 8 mm
- универсальный зажим-соединитель для проволоки - multipurpose clamp for wire
- опуск токоотвода - downdrop
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. |
ZZ-201-008-3 |
ZANDZ Lightning arrester mast, vertical, 8 m high, with a set of 2 wall fasteners (stainless steel) |
1 |
|
|
|
2. |
ZZ-202-002 |
ZANDZ Interception rod terminal, D42 mm for current collectors (stainless steel) |
1 |
|
|
|
3. |
GL-11149-50 |
GALMAR Copper-plated wire (D 8 mm/S 50 mm²; 50-meter bundle) |
1 |
0,41 |
Weight per 1 m |
|
4. |
GL-11545A |
GALMAR Main conductor rain water gutter terminal (painted galvanized steel) |
4 |
0,112 |
|
|
5. |
GL-11551A |
GALMAR Terminal for connecting current collectors (painted zinc-plated steel) |
10 |
0,07 |
|
|
6. |
GL-11711 |
GALMAR Flat roof terminal for the main conductor cable (D8 mm; plastic, concrete) |
45 |
1,20 |
|
|
7. |
GL-11703A |
GALMAR Current collector facade clamp providing 15 mm elevation of the collector over the clamp (painted zinc-plated steel) |
15 |
0,02 |
|
|
8. |
GL-11514N |
GALMAR Ring clamp on rainwater pipe for current collector (tinned copper) |
4 |
0,076 |
|
|
GROUNDING ARRANGEMENT: |
|||||
|
9. |
GL-11075-20 |
GALMAR Copper-plated strip (30*4 mm/ S 120 mm²; 20-meter strip bundle) |
1 |
0,98 |
Weight per 1 m |
|
10. |
ZZ-001-065 |
ZANDZ Copper-plated threaded grounding rod (D14; 1.5 m) |
4 |
2,00 |
|
|
11. |
ZZ-002-061 |
ZANDZ Threaded coupling |
3 |
0,08 |
|
|
12. |
ZZ-003-061 |
ZANDZ Termination |
2 |
0,07 |
|
|
13. |
ZZ-004-060 |
ZANDZ Guide head for jackhammer attachment |
1 |
0,09 |
|
|
14. |
ZZ-005-064 |
ZANDZ Conductor connection terminal (up to 40 mm) |
5 |
0,312 |
|
|
15. |
ZZ-006-000 |
ZANDZ Conductive grease |
1 |
0,10 |
|
|
16. |
ZZ-007-030 |
ZANDZ Waterproofing tape |
2 |
0,40 |
|
|
17. |
ZZ-008-000 |
ZANDZ Attachment to the hammer (SDS max) |
1 |
0,50 |
|
Do you have any questions regarding lightning protection and grounding of the compressor workshop? Please contact the ZANDZ Technical Center!
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