Sometimes, we have to protect really large facilities against lightning. A car assembly workshop having a total area over 50,000 sq. m was one of them.
Although the grid can be installed on buildings with flat roofs, it does not provide protection against direct lightning strike. The customer did not like this lightning protection method, therefore, lightning rods were the only option.
To provide lightning protection for the workshop, we had to use about 170 lightning arresters on three concrete foundations 4 to 6 meters high. Only this amount allowed to provide reliability corresponding to Zone B according to RD 34.21.122-87.
Let's consider our solution in more details.
Task
To calculate lightning protection for the car assembly workshop.
Solution
Calculations of the lightning protection system for the car assembly workshop are made in conformity with the following regulatory documents:
- "Electrical Installations Code" (further – EIC), EIC 7th edition.
- "Instructions for the installation of lightning protection of buildings, structures, and industrial communications" SO 153-34.21.122-2003 (further – SO).
- "Instructions for mounting the lightning protection of buildings and structures" Working Documentation 34.21.122-87 (further – WD).
The lightning arresters are used to protect the buildings against lightning strokes. The lightning arrester consists of an interception rod, intercepting a lightning discharge, the main conductor cable, and the ground electrode. All these elements let us divert lightning current into the ground safely, without any damage to the protected facility.
The car assembly workshop is classified as Category 3 according to RD and as a special facility with the limited hazard in terms of lightning protection according to SO.
Description of the lightning protection system for the car assembly workshop
A set of arrangements ensuring compliance with the lightning protection requirements is based on the following solutions:
- 161 lighting rods are installed on three concrete foundations 4 m high.
- 8 lightning rods are installed on three concrete foundations 6 m high.
- Current collectors are laid from lightning arresters using a zinc-coated wire D = 8 mm, and they are connected to the artificial grounding arrangement.
- The lightning arresters are interconnected to arrange two current collectors from each lightning arrester.
- The main conductor cables are mounted (installation step 0.6-1 m):
- on a flat roof using clamps GL-11711;
- on the walls using clamps GL-11703A.
- Connection and branching of main conductors are usually made using terminals GL-11551A.
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 clause 2.13 WR, only a circuit, without the installation of vertical electrodes is considered as sufficient.
- The horizontal electrodes are connected to each other using connection terminal ZZ-005-064.
- The connection of the main conductor cable with the output of the galvanized ground strip is performed with the control terminal GL-11562A.
- The design of the grounding arrangement corresponds to clause 1.7.55 of 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 Figure 1. The depicted protection area corresponds to area B, constructed as per Appendix 3 of WD.
Picture 1. Layout of lightning protection and grounding arrangement elements for the car assembly workshop (to request a full-size image, write to info@zandz.com).
Components of the lightning protection system for the car assembly workshop
Do you have any questions regarding the calculation of the lightning protection and grounding of the car assembly workshop? Please, contact the ZANDZ Technical Center!
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