The ZANDZ Technical Center has received a request to calculate the lightning protection and grounding system for a mobile heat supply station. Let us consider the proposed solution.
facility: mobile heat supply station;
dimensions: 6.06 m x 2.5 m;
height: 2.6 m;
soil resistivity 100 Ohm*m.
To calculate the internal lightning protection system and a grounding arrangement.
Lightning protection and grounding of the building are made in accordance with:
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" from the viewpoint of SO and as Category III of the lightning protection according to RD.
According to the EIC Rev. 7, item 1.7.1033, the resistance of the grounding arrangement should not be more than 10 Ohm in any season of the year.
A set of measures to provide necessary requirements to the lightning protection system and to the grounding arrangement for the mobile heat supply station includes the following solutions:
According to SO, item 188.8.131.52, a metal facility roof is used as a lightning arrester.
The metal structure of the facility is used as a current collector.
Transient resistance between all metal sheets and panels should not be more than 0.05 Ohm with mandatory annual control of resistance before the storm season, according to RD, item 3.4.
All metal elements located on the roof should be connected to the metal facility structure.
All reinforced concrete foundations and basements should be used as natural grounding arrangements and connected to the artificial grounding arrangement.
3 m steel copper-plated electrodes are used as vertical grounding arrangements in the locations connection to metal structures.
A steel copper-plated bar having cross-section 30 x 4 mm is used as a horizontal grounding arrangement as a circuit according to RD, item 2.26. The distance to the facility foundation is at least 1 m. Strip deepening is 0.5 to 0.7 m.
Connection to the grounding arrangement is made through clamps ZZ-005-064.
According to the EIC, Rev. 7, item 1.7.55, grounding devices for protective grounding of electrical installations for buildings and structures and Categories 2 and 3 of the lightning protection for these buildings and structures usually should be common.
Ground terminal resistance calculation:
Vertical electrode resistance:
Ом - Ohm
Верт - Vert
Экв - Eq
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 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;
Lhor is horizontal electrode length, 25 m.
Electrical impedance of the grounding arrangement:
Ом - Ohm
ЗУ - GA
where n is a number of sets, vertical grounding arrangements - 2 pcs, horizontal grounding arrangement - 1 pc;
Kutil is utilization rate, 0.75.
The calculated resistance of the grounding arrangement is 6,77 Ohm.
The location of the equipment is shown in Figure 1.
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-11075-20||GALMAR Copper-plated strip (30 * 4 mm/ S 120 mm²; 20-meter strip bundle)||1||0,98||Вес 1 метра|
|2.||GL-11075-10||GALMAR Copper-clad strip (30x4 mm/S 120 mm²; 10-meter strip bundle)||1||0,98||Вес 1 метра|
|3.||ZZ-001-065||ZANDZ Copper-plated threaded grounding rod (D14; 1,5 m)||4||2,00|
|4.||ZZ-002-061||ZANDZ Threaded coupling||3||0,08|
|6.||ZZ-004-060||ZANDZ Guide head for jackhammer attachment||1||0,09|
|7.||ZZ-005-064||ZANDZ Conductor connection terminal (up to 40 mm)||7||0,312|
|8.||ZZ-006-000||ZANDZ Conductive grease||1||0,15|
|9.||ZZ-007-030||ZANDZ Waterproofing tape||2||0,40|
|10.||ZZ-008-000||ZANDZ Attachment to the hammer (SDS max)||1||0,50|
Do you have any questions regarding lightning protection and grounding of a mobile heat supply station? Please contact the ZANDZ Technical Center.