The ZANDZ Technical Center has received a request to calculate lightning protection and grounding systems for a waste paper warehouse. Let us consider the solution proposed by our engineers.
Facility: waste paper warehouse.
Protected facility dimensions: 31 m x 30 m x 5.37 m.
Ridge height: 7.82 m.
The soil resistivity accepted for calculations is 100 Ohm * m.
Calculate the external lightning protection system.
Calculate the grounding device.
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 referred to as RD.
The facility is classified as conventional, according to SO and to Category 3, according to RD. The required system reliability is at least 0.9.
A set of arrangements to ensure compliance with the requirements of the lightning protection system for the waste paper warehouse is based on the following solutions:
The lightning protection of the facility is made using ridge lightning arresters (GL-11521SS) attached using clamps GL-11525 as well as using vertical elevations of current collectors by 1 m along the roof edges.
A copper-plated steel wire (copper coating thickness is at least 70 μm), d8 mm (GL-11149) is used as a current collector.
Installation of current collectors is performed using clamps GL-11747A on the roof and GL-11703A on ramparts and vertical surfaces. The clamp installation interval 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 Categories 2 and 3 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 calculation performed using the software developed by Krzhizhanovsky Energy Institute (OAO ENIN):
Intensity of lightning discharge into the ground is 4 strikes/square km/year;
The total number of strikes into the system is 0.024 (once every 42 years).
The total number of breakouts into the system is 0.0024 (once every 417 years).
The system reliability is 0.901..
The probability of a breakout into all facilities of the system is 0.099.
Ground terminal resistance calculation:
Vertical electrode resistance:
Верт - Vert
Ом - Ohm
where ρeq is equivalent soil resistivity, 100 Ohm·m;
L is vertical electrode length, 3 m;
d is vertical electrode diameter, 0.014 m;
T is depth, i.e. the distance from the ground surface to the ground electrode, 2 m;
м - m
where t is electrode top depth, 0.5 m.
Horizontal electrode resistance:
Ом - Ohm
where ρeq 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, 30 m.
Electrical impedance of the grounding arrangement:
Ом - Ohm
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 device is 5,51 Ohms.
The layout of the equipment is shown in Figure 1.
Figure 1. Equipment layout.
The list of equipment and necessary materials is provided in Table 1.
Условные обозначения - Legend
- молниеприемник коньковый высотой 2 м - ridge lightning arrester 2 m high
- вертикальное возвышение молниеотвода 0,5 м - vertical elevation of the lightning arrester 0.5 m
- проволока стальная омедненная диаметром 8 мм - steel copper-plated wire 8 mm
- полоса стальная омедненная сечением 30х4 мм - steel copper-plated bar with cross-section 30 x 4 mm
- зажим для подключения проводника - wire connection clamp
- опуск токоотвода - downdrop
- вертикальный заземлитель длиной 3 м - 3 m vertical grounding electrode
Table 1. List of needed materials.
|№||Part number||Name||Quantity, pcs.||Unit weight, kg.||Note|
|1.||GL-11521SS||GALMAR 2 m lightning rod for mounting in threaded holders (M16; stainless steel)||3||10|
|2.||GL-11525||GALMAR Air terminal crest holder (M16 thread; conductor terminal of d10 mm; bronze)||3|
|3.||GL-11149-50||GALMAR Copper-plated wire (D 8 mm/S 50 mm²; 50-meter bundle)||1||0,41||Вес 1 м|
|4.||GL-11149-20||GALMAR Copper-plated wire (D 8 mm / S 50 mm²; 20-meter coil)||1||0,41||Вес 1 м|
|5.||GL-11551A||GALMAR Conductor connection clamp (painted zinc-plated steel)||10||0,07|
|6.||GL-11747A||GALMAR Conductor roof clamp for the roof coated with metal shape / corrugated sheeting (painted galvanized steel)||180||0,05|
|7.||GL-11703A||GALMAR Conductor front terminal providing 15mm elevation of the main conductor over the terminal (painted galvanized steel)||20||0,02|
|8.||GL-11075-20||GALMAR Copper-plated bar (30 * 4 mm / S 120 mm²; bundle 20 meters)||2||0,98||Вес 1 м|
|9.||ZZ-001-065||ZANDZ Copper-plated threaded grounding rod (D14; 1,5 m)||4||2,00|
|10.||ZZ-002-061||ZANDZ Threaded coupling||3||0,08|
|12.||ZZ-004-060||ZANDZ Guide head for jackhammer attachment||1||0,09|
|13.||ZZ-005-064||ZANDZ Conductor connection terminal (up to 40 mm)||6||0,312|
|14.||ZZ-006-000||ZANDZ Conductive grease||1||0,10|
|15.||ZZ-007-030||ZANDZ Waterproofing tape||2||0,40|
|16.||ZZ-008-000||ZANDZ Attachment to the hammer (SDS max)||1||0,50|
Do you have any questions regarding lightning protection and grounding system for the waste paper warehouse? Please contact the ZANDZ Technical Center!