Colleagues, did any of you think wether it is safe to walk on bridges and overground pedestrian overcrossings during a thunderstorm? The designers contacted our ZANDZ Technical Center with a task to calculate and justify such a project. It turns out that there is a real interest in this issue. When designing a shopping center in Tchelyabinsk, near which there was an overcrossing (elevated pedestrian crossing), there arose a question: how to protect people from lightning strikes when crossing this overcrossing?
ZANDZ Technical Center the engineers performed the calculations and proposed a solution, which we will study further.
A set of measures to ensure the necessary requirements for the grounding device and lightning protection system of the elevated pedestrian overcrossing is presented by the following solutions:
1. Lightning protection and grounding are made in accordance with EIC-7 ed. "Rules for electrical installations", IS 153-34.21.122-2003 "INSTRUCTIONS ON THE ARRANGEMENT OF LIGHTNING PROTECTION OF BUILDINGS, CONSTRUCTIONS AND INDUSTRIAL COMMUNICATIONS" and AD 34.21.122-87 "INSTRUCTION ON THE ARRANGEMENT OF LIGHTNING PROTECTION OF BUILDINGS AND STRUCTURES".
2. The object refers to category 3 of lightning protection.
3. According to IS 153-34.21.122-2003, paragraph 22.214.171.124 metal lighting masts are used as lightning rods.
4. Metal columns are used as down conductors.
5. Transient resistance between all metal current-conducting parts must be not more than 0,05 Ohm at an obligatory annual control before the storm season in accordance with AD 34.21.122-87,p. 3.4.
6. All metal elements placed on the overhead pedestrian overground must be connected to a circuit made under an asphalt surface.
7. All reinforced concrete foundations, plinth walls must be used as natural ground electrodes and be connected to the artificial grounding device.
8. Steel copper-bonded groundconductors 3 m long are used as vertical ground electrodes.
9. Copper-bonded steel tape with the cross-section of 30x4 mm in the form of a circuit is used as a horizontal ground electrode in accordance with AD 34.21.122-87, p.2.26. The distance to the object foundation- not less than 1 m. Burial depth of the tape 0,5-0,7 m.
10. The calculated value of the grounding device resistance is 3.75 Ohms.
11. Connection to the grounding device is carried out with the help of clamps ZZ-005-064.
12. In accordance with the EIC-7 ed., p.1.7.55 - 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.
Grounding device resistance calculation:
The design resistance of the grounding device is 3,75 ohms.
Figure 1 shows the arrangement of equipment.
Figure 1 - Location of the grounding device.
Условные обозначения – Type Codes
Полоса стальная оцинкованная сечением 30* 4 проложенная под асфальт – Steel galvanized tape with the cross section 30*4 mm laid under the asphalt
Полоса стальная оцинкованная сечением – Steel galvanized tape with the cross section of 30*4
Зажим для соединения проводников – clamp for connecting conductors
Вертикальный заземлитель – vertical ground electrode
The list of required equipment and materials is given in table 1.
Table 1 - List of required equipment and materials.
|№||Product item||Name||Quantity, pcs.||Mass, kg||Note|
|1.||GL-11075-50||GALMAR Copper-bonded tape (30 * 4 mm / S 120 mm²; coil of 50 meters)||5||0,98||В метрах|
|2.||ZZ-001-065||ZANDZ Copper-coated threaded grounding rod (D14; 1.5 m)||8||2,00|
|3.||ZZ-002-061||ZANDZ Threaded coupler||5||0,08|
|4.||ZZ-003-061||ZANDZ Starting tip||4||0.07|
|5.||ZZ-004-060||ZANDZ Driving head for a jackhammer||2||0,09|
|6.||ZZ-005-064||ZANDZ Clamp for connecting conductor (up to 40 mm)||20||0,16|
|7.||ZZ-006-000||ZANDZ Conductive grease||1||0,10|
|8.||ZZ-007-030||ZANDZ Waterproof tape||5||0,40|
|9.||ZZ-008-000||ZANDZ Header for a jackhammer (SDS max)||1||0,50|
Do you have questions or need to calculate a lightning protection and / or grounding system for overground pedestrian overcrossings? Send your request to firstname.lastname@example.org.