The ZANDZ Technical Centre has received a request to calculate the lightning protection system and grounding arrangement for a community center. Let's consider the solution proposed by our engineers.
1. Facility: a community centre.
2. Architectural drawings of the facility (roof plan, facades).
3. Facility height: 7.05 and 9.36 m.
4. Soil resistivity: 100 Ohm*m.
1. Calculate the external lightning protection system.
2. Calculate the grounding device.
The activities have been performed according to:
1. EIC Rev. 7 (hereinafter referred to as the EIC);
2. SO 153-34.21.122-2003 Instructions for Mounting Lightning Protection for Buildings, Structures, and Industrial Utilities (hereinafter referred to as SO);
3. RD 34.21.122-87 Instructions for Mounting Lightning Protection for Buildings and Structures (hereinafter referred to as RD).
According to the EIC Rev. 7, item 1.7.103. the resistance of the grounding arrangement should not be more than 10 Ohmin any season of the year.
A set of measures to meet the necessary requirements to the lightning protection system and to the grounding arrangement includes the following solutions:
The facility is classified as Category III (IV) in terms of lightning protection. The system's reliability should be not less than 0.8-0.9.
The lightning protection of the facility is made by lightning arresters (GL-21131), which are secured using a concrete foundation, and by 4 m lightning rods (ZZ-201-004), which are secured to vertical surfaces by holders (ZZ-203-001), and connection to current collectors is made by clamps (ZZ-202-001).
A copper-plated steel wire (copper coating thickness is at least 70 μm), d8 mm (GL-11149) is used as a current collector.
Current collectors are installed using clamp ZZ-202-015 on the roof and GL-11703A on vertical surfaces. The clamp installation step is 0.8 to 1.0 m.
The multipurpose GL 11551A clamp is used to connect the rolled products over the length and in assemblies.
All metal elements located on the roof should be connected to current collectors.
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.
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.
If there are concrete-steel constructions, they shall be connected to down conductors/grounding device.
Connection to the grounding device is carried out using ZZ-005-064 clamps.
Results of the calculations performed by using the software developed by OAO Krzhizhanovsky Energy Institute (OAO ENIN):
the density of lighting discharges into the ground is 4 strikes/sq. km per year;
the total number of strikes into the system is 0.042 (once every 24 years);
the total amount of breakthroughs (the strikes directly into the facility bypassing lightning arresters) is 0.0033 (once every 303 years);
the system's reliability is 0.923.
Ground terminal resistance calculation:
Vertical grounding arrangement resistance:
Верт - Vert
Ом - Ohm
where ρ – is equivalent soil resistivity, 100 Ohm·m;
L – is vertical electrode length, 3 m;
d is vertical electrode diameter, 0.014 m;
T is deepening;
t is the distance from the ground surface to the grounding arrangement, 0.5 m;
м - m
Horizontal grounding arrangement resistance:
Гор - Hor
Ом - Ohm
where ρ is soil resistivity, 100 Ohm·m;
b is horizontal electrode width, 0.03 m;
h is horizontal grounding depth, 0.7 m;
Lhor is horizontal electrode length, 170 m.
Electrical impedance of the grounding arrangement:
ЗУ - GA
Ом - Ohm
where n is number of vertical grounding arrangements - 8 pcs; horizontal grounding arrangements - 1 pc;
kutil – is utilization rate, 0.69
rated resistance of the grounding arrangement is 1,52 Ohm, which is less than the required value of 10 Ohms.
Условные обозначения - Legend
- молниеприемник на бетонном основании высотой 2 м - 2 m lightning arrester on a concrete foundation
- молниеприемник мачта высотой 4 м- 4 m lightning rod
- проволока стальная омедненная диаметром 8 мм - steel copper-plated wire with a diameter 8 mm
- полоса стальная омедненная сечением 30х4 мм - steel copper-plated bar 30 x 4 mm
- зажим для подключения проводника - clamp for wire connection
- опуск токоотвода - downdrop
- вертикальный заземлитель длиной 3 м - 3 m vertical grounding arrangement
Figure 1. Layout of lightning protection and grounding system components.
The list of necessary equipment and materials is provided in Table 1.
Table 1. List of required materials.
|№||Part number||Name||Quantity, pcs||Unit weight, kg||Note|
|1.||GL-21131||GALMAR Lightning arrester (2 meters; 1 m on a concrete foundation, zinc-plated steel; complete with the clamp for the stainless steel current collector)||14|
|2.||ZZ-201-004||ZANDZ Vertical lightning mast, 4 m (stainless steel)||3||8,5|
|3.||ZZ-203-001||ZANDZ Wall fastening for interception rod (stainless steel)||3||14,665|
|4.||ZZ-202-001||ZANDZ Interception rod terminal for main conductor cables (stainless steel)||3||0,2|
|5.||GL-11149-50||GALMAR Copper-clad wire (D 8 mm/S 50 mm²; 50-meter bundle)||9||0,41||Вес 1 метра|
|6.||GL-11551A||GALMAR Conductor connection clamp (painted zinc-plated steel)||70||0,07|
|7.||ZZ-202-015||ZANDZ Holder for a circular conductor on a flat roof (D 8 mm; plastic + concrete)||450||1,00|
|8.||GL-11703A||GALMAR Current collector facade clamp providing 15 mm elevation of the collector over the clamp (painted zinc-plated steel)||140||0,02|
|9.||GL-11075-50||GALMAR Copper-plated strip (30 * 4 mm / S 120 mm²; 50-meter strip bundle)||4||0,98||Вес 1 метра|
|10.||ZZ-001-065||ZANDZ Copper-plated threaded grounding rod (D14; 1.5 m)||16||2,00|
|11.||ZZ-002-061||ZANDZ Threaded coupling||9||0,08|
|13.||ZZ-004-060||ZANDZ Guide head for jackhammer attachment||4||0,09|
|14.||ZZ-005-064||ZANDZ Conductor connection terminal (up to 40 mm)||21||0,312|
|15.||ZZ-006-000||ZANDZ Conductive grease||1||0,10|
|16.||ZZ-007-030||ZANDZ Waterproofing tape||7||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 for a community centre or other facilities? Please, contact the ZANDZ Technical Center!