The development of oil fields in remote areas is usually accompanied by the construction of buildings in which the personnel will live. The ZANDZ Technical Center received a request for calculation of lightning protection of one of these buildings - a hostel located in the oil and gas condensate field.
Near the hostel there are lightning poles with the height of 24 m. Therefore, at first, our engineers estimated whether they can be used as lightning rods. Having found out that the masts provide only partial lightning protection of the building, they proposed to install additional lightning rods to bring the reliability of protection against lightning to the required level. Let's see the solution presented to the customer in more detail.
Task
To calculate lightning protection of a hostel at an oil field. The building under protection is an ordinary structure in terms of lightning protection in accordance with the IS and is in Category 3 according to the AD.
Solution
The calculations are made in accordance with the following documents:
- Electric Installation Code" EIC 7th ed. (hereinafter - EIC).
- Instructions for organization of lightning protection of buildings, structures and industrial communications" IS 153-34.21.122-2003 (hereinafter IS).
- Instructions for lightning protection of buildings and structures" AD 34.21.122-87 (hereinafter - AD).
Protection of buildings from lightning strikes is carried out with the help of lightning rods. A lightning rod is a device rising above the facility that diverts lightning current into the ground without entering the facility. It consists of a lightning rod which directly takes the lightning discharge upon itself, a down conductor and a ground electrode.
Description of external lightning protection system of a hostel
The set of measures to provide the required lightning protection is offered by the following solutions:
- 2 existing masts 24 m high are used.
- Installation of 2 rods 8 m high, fixed to the wall is additionally carried out. It is taken into account that 1 m of the lightning rods height is used for fixation;
- Lightning rods are interconnected to arrange two down conductors, using copper-bonded wire D=8 mm from each lightning rod. Down conductors are connected to the artificial ground electrode. Fixation of down conductors is carried out (installation distance 0.6-1 m):
- to the wall – with a GL-11703A clamp;
- on the roof slopes using clamps GL-11747A.
- GL-11551A clamps are used to connect and branch the down conductors.
The set of measures on the provision of the necessary requirements to the grounding device is presented by the following solutions:
- A horizontal electrode (galvanized steel strip 4x30 mm) is laid from the down conductor downdrops, 0.5 meter deep to the existing ground loop laid around the building.
- Interconnection of horizontal electrodes is carried out by using clamp ZZ-005-064.
- The down conductor is connected to the galvanized tape protruding from the ground with the help of GL-11562M clamp.
- Protective grounding is carried out in accordance with paragraph 1.7.55 of the EIC “grounding devices for protective grounding of electrical installations of buildings and structures and lightning protection of the 2nd and 3rd categories of these buildings and structures, as a rule, should be common.
The layout of elements in the lightning protection system and the grounding device is shown in Figure 1. The protection zone is built for the reliability of 0.9 IS.
Figure 1. Plan with the layout of lightning protection elements and grounding device
Calculation of the reliability of lightning protection in the program
The following source data are taken for the calculation:
The density of lightning discharges into the ground is 2 strikes / sq.
The results of lightning protection calculation performed by the software, developed by OJSC "Energy Institute to the name of Krzhizhanovsky" (OJSC" ENIN ") are given in table 1. Source data and calculation results in pdf file.
Chart 1 - Results of lightning protection calculation
|
№ |
Object |
Lightning rod height, m |
Protection reliability |
Number of strikes into an object, year-1 |
Number of breakthroughs into the object, year-1 |
|
Period of srikes, year |
Period of breakthroughs, year |
||||
|
1 |
Hostel |
8 м |
0,9915 |
0,065 |
0,00055 |
|
every 15 years |
every 1818 years |
Accessories for the external lightning protection system of a hostel
Chart 2 - List of materials needs
|
№ п/п |
Fig. |
Product item |
Product |
Quantity |
|
Lightning protection system |
||||
| 1. |  |
ZZ-201-008-3 | ZANDZ Vertical air-terminal mast 8 m with a set of 2 fastenings to the wall (stainless steel) | 2 |
| 2. |  |
ZZ-202-002 | ZANDZ Clamp to the lightning rod D42 mm for down conductors (stainless steel) | 2 |
| 3. |  |
GL-11149-50 | GALMAR Copper- bonded steel wire (D8 mm; coil of 50 meters) | 2 |
| 4. | |
GL-11149-10 | GALMAR Copper-bonded steel wire (D8 mm; coil of 10 meters) | 1 |
| 5. |  |
GL-11551A | GALMAR Clamp for connecting down conductors (painted galvanized steel) | 2 |
| 6. |  |
GL-11747A | GALMAR Clamp for the roof covered with metal profiles / corrugated sheets, for down conductor (painted galvanized steel) | 48 |
| 7. |  |
GL-11703A | GALMAR Clamp to the facade / wall for a down conductor with elevation (15 mm high; painted galvanized steel) | 60 |
| 8. |  |
GL-11562A | GALMAR Control clamp for connecting down conductors, wire + tape (painted galvanized steel) | 4 |
|
Grounding device |
||||
| 9. |  |
ZZ-005-064 | 4 | |
| 10. |  |
ZZ-502-304-6 | ZANDZ galvanized steel tape (30 * 4 mm; cut of 6 m) | 2 |
Do you have any questions on calculation of lightning protection? Please contact our ZANDZ Technical center!
See also: