Calculation of external lightning protection for malls and trade and service centers is one of the most popular requests sent by designers and owners of the facilities to the ZANDZ.com Technical Center. They are often buildings having large roof area where the climatic equipment, advertising structures, zenith lights, etc. are used.
Recently, ZANDZ.com Technical Center has received a request to calculate the external lightning protection system for stage P design wherein the presence of the equipment and other structures on the roof was not considered.
According to SO 153-34.21.122-2003 "INSTRUCTIONS FOR ARRANGEMENT OF LIGHTNING PROTECTION OF BUILDINGS, STRUCTURES AND INDUSTRIAL UTILITIES" (hereinafter, SO), the trading structures not higher than 60 meters are classified as "conventional". The lightning strike to such structures leads to power supply and fire system failure. Considering that the roof of a trade and service center is not operated, the ZANDZ Technical Center has proposed to use the lightning grid.
According to RD (item 2.11), protection of Category II buildings and structures with non-metal roofs against direct lightning strikes, if the roof inclination does not exceed 1:8, can be made using a lightning grid subject to mandatory fulfilling of the requirements provided in item 2.6. The lightning grid should be made of steel wire having a diameter of at least 6 mm and installed on the roof from the top or under the inflammable or poorly flammable thermal insulation or water proofing. The grid cell spacing should not be more than 6 x 6 m. Grid nodes should be welded.
A set of arrangements ensuring compliance with the lightning protection requirements is based on the following solutions:
- the facility's lightning protection is made as a lightning grid using a galvanized steel wire with a diameter 8 mm laid with a step of not more than 12 x 12 m. The grid is made such that the current would have at least two different paths to the grounding arrangement, downdrops to the current collectors are made at least every 25 m along the building perimeter;
- current collectors are mounted (installation step 0.6-1 m):
- metal ladders are connected to grid current collectors using clamps ZZ-005-064;
- connection and branching of current collectors are made using clamps GL-11551А.
A set of measures to ensure the requirements for the grounding arrangement is based on the following solutions:
- assembly of a grounding arrangement, consisting of a horizontal electrode (galvanized steel strip with a cross-section of 4x30 mm), to a depth of 0.5 m, laid along the perimeter of the building at a distance of 1 m from the foundation;
- as per item 2.13 of RD, only a circuit, without the installation of vertical electrodes, is considered to be sufficient;
- horizontal electrodes are interconnected using clamp ZZ-005-064;
- current collector is connected to the output of the galvanized ground strip using control clamp GL-11562A;
- the design of the grounding arrangement corresponds to item 1.7.55 of the EIC. Grounding arrangements for protective grounding and grounding for lightning discharges are common.
The location of the elements of the lightning protection system and the grounding arrangement is shown in the figure below. The indicated protection zone corresponds to the zone B according to RD.
Условные обозначения: Key legend:
- горизонтальный заземлитель; - horizontal grounding electrode;
- токоотвод; - current collector;
- зажим для подключения проводника - clamp for connecting conductor
- зажим для соединения токоотводов - clamp for connecting current collector
- зажим контрольный (проволока + полоса) - control clamp (wire + bar)
Table 1. List of required materials.
|Item #||Fig.||Part number||Product||Quantity|
|Lightning protection system|
|1||ZZ-502-008-125||ZANDZ Galvanized steel wire (D 8 mm / S 50 mm²; wire bundle 125 m)||5|
|2||GL-11703A||GALMAR Clamp for fastening the current conductor with elevation (15 mm height; painted galvanized steel) to the facade/wall||110|
|3||ZZ-202-015||ZANDZ Holder for a circular conductor on a flat roof (D 8 mm; plastic + concrete)||500|
|4||GL-11551A||GALMAR Clamp for current conductors connection (painted galvanized steel)||35|
|5||GL-11562A||GALMAR Control clamp wire + bar (painted galvanized steel) for connecting current collectors||8|
|6||ZZ-005-064||ZANDZ Conductor connection clamp (up to 40 mm)
(до 40 мм)
|7||ZZ-502-304-52||ZANDZ Galvanized steel strip (30 * 4 mm; 52 m bundle)||4|
|8||ZZ-007-030||ZANDZ Waterproofing tape||4|
Do you have any questions about lightning protection for the cadet school or other facilities? Please contact the ZANDZ Technical Center!