The ZANDZ Technical Center has received a request to calculate the lightning protection system and grounding arrangement for water tanks. Let's consider the solution proposed by our engineers.
The activities have been performed according to:
- EIC, Rev. 7. Electrical Installations Code (hereinafter referred to as the EIC);
- SO 153-34.21.122-2003 Instructions for Mounting Lightning Protection for Buildings, Structures, and Industrial Utilities (hereinafter referred to as SO);
- RD 34.21.122-87 Instructions for Mounting Lightning Protection for Buildings and Structures (hereinafter referred to as RD);
- GOST 31385-2016.
vertical stock tank diameter: 9 m;
vertical stock tank height: 5.39 m;
soil resistivity 100 Ohm*m.
Task: to calculate lightning protection and grounding for the facility.
A set of measures to provide necessary requirements to the lightning protection and grounding system for the vertical stock tank for storing water includes the following solutions:
1. The facility is classified as "conventional" according to SO 153-34.21.122-2003 and as Category 3 according to RD 34.21.122-87.
2. According to SO 153-34.21.122-2003, item 22.214.171.124, the metal structure of the facility is used as a lightning arrester and current collectors.
3. Transient resistance between all metal sheets and panels should not be more than 0.05 Ohm with the mandatory annual control of resistance before the storm season according to RD 34.21.122-87, item 3.4.
4. All metal elements must be connected to the metal structure/grounding.
5. 3 m copper-plated steel electrodes in the locations of current collector downdrops are used as vertical ground electrodes.
6. According to GOST 31385-2016, item 126.96.36.199, a lower band of the tank wall should be connected via current collectors to the grounding electrodes installed at the distance of not more than 20 m around the wall perimeter but at least four at equal distances.
7. The copper-plated steel strip with a cross-section 30 x 4 mm, combining all vertical electrodes, is used as a horizontal grounding electrode. The distance to the facility foundation is at least 1 m. Strip deepening is 0.5 to 0.7 m.
8. According to the EIC, Rev. 7, 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.
9. Design resistance of the grounding arrangement is 2.71 Ohms.
10. If there are reinforced concrete structures, they should be connected to current collectors or to the grounding device.
11. Connection to the grounding device is performed using ZZ-005-064 clamps.
Ground terminal resistance calculation:
Vertical electrode resistance:
Верт - Vert
Экв - Eq
Ом - Ohm
where ρρeq – 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;
where t – is electrode top depth, 0.5 m.
Horizontal electrode resistance:
Гор - Hor
Ом - Ohm
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, 83 m.
Electrical impedance of the grounding arrangement:
ЗУ - GA
Ом - Ohm
where n is a number of sets, vertical grounding arrangements - 12 pcs, horizontal grounding arrangement - 1 pc;
Kutil is utilization rate, 0.5.
Calculated resistance of the grounding arrangement is 2,71 Ohm.
Условные обозначения - Legend
- полоса стальная омедненная сечением 30 х 4 мм - steel copper-plated bar 30 x 4 mm
- зажим для подключения проводника - clamp for connecting conductor
- подключение к заземляющему устройству - connection to grounding arrangement
- вертикальный заземлитель длиной 3 м - 3 m vertical grounding arrangement
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|
|1.||GL-11075-50||GALMAR Copper-plated bar (30 * 4 mm/S 120 mm²; 50-meter bundle)||2||0,98||Вес 1 м|
|2.||ZZ-001-065||ZANDZ Copper-plated threaded grounding rod (D14; 1,5 m)||24||2,00|
|3.||ZZ-002-061||ZANDZ Threaded coupling||13||0,08|
|4.||ZZ-003-061||ZANDZ Takeoff tip||12||0,07|
|5.||ZZ-004-060||ZANDZ Guide head for jackhammer attachment||5||0,09|
|6.||ZZ-005-064||ZANDZ Conductor connection terminal (up to 40 mm)||26||0,312|
|7.||ZZ-006-000||ZANDZ Conductive grease||2||0,10|
|8.||ZZ-007-030||ZANDZ Waterproofing tape||9||0,40|
|9.||ZZ-008-000||ZANDZ Attachment to the hammer (SDS max)||1||0,50|
Do you have any questions regarding grounding and lightning protection of vertical stock tanks for storing water? Please contact the ZANDZ Technical Center!