One of recent inquiries received by the ZANDZ Technical Center includes a request to calculate the lightning protection system for the uncovered lumber storage in the Irkutsk Region. Such industrial facilities are common in our country because it is rich in forests. Therefore, we would like to share, with the specialists, our solution to provide lightning protection for such facility.
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Design and arrangement of the storage facilities are governed by SP 114.13330.2016. According to this document, the lightning protection of the storage should be made according to protection level III provided in instructions SO 153-34.21.122-2003. The latter document does not provide for the exact design option for the lightning protection and grounding system.
In our case, the ZANDZ specialists have proposed to make the lightning protection system based on standalone lightning arresters explaining the choice by large facility area. The reasoning behind the choice, lightning arrester design, their amount and locations, as well as construction of grounding arrangements are provided in our calculation.
Task
To calculate the lightning protection for the lumber storage.
Solution
Calculations of the lumber storage lightning protection are made in conformity with the following documents:
- "Electrical Installations Code" (hereinafter, the EIC), EIC 7th edition.
- "Instructions for the installation of lightning protection of buildings, structures, and industrial communications" SO 153-34.21.122-2003 (hereinafter, SO).
- "Instructions for mounting the lightning protection of buildings and structures" Working Documentation 34.21.122-87 (hereinafter, RD).
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 lumber storage is classified as a conventional facility in terms of lightning protection according to SO and to Category 3 according to RD.
Description of the lightning protection system for the lumber storage
A set of arrangements ensuring compliance with the lightning protection requirements is based on the following solutions:
- 52 x 4 m lightning rods are installed on 11 m wooden supports. It is considered that 1 m of the rod length is used for securing.
- A current collector made of a zinc-plated wire D = 8 mm is installed from the lightning arrester to the grounding arrangement. The current collector is secured (installation spacing 0.6-1 m) using clamps GL-11703A.
A set of measures to ensure the requirements for the grounding arrangement is based on the following solutions:
- Laying a horizontal ground electrode for current spreading in two directions with an angle of 90 degrees between them. Length of each ground electrode is 2.5 m. The ground electrode is made of a corrosion-resistant steel copper-plated strip with a cross-section of 4 x 30 mm, the laying depth is 0.5 m.
- At the end of the horizontal ground electrode, one vertical electrode with the length of 3 m is installed in each directions.
- The connection of the current collector with bringing out the zinc-plated ground bar is performed using control clamps GL-11562A.
- The connection of vertical and horizontal electrodes is carried out using clamps ZZ-005-064.
The location of the elements of the lightning protection system and the grounding arrangement is shown in Figure 1.
Figure 1. Lightning protection element layout for the lumber storage (write to e-mail info@zandz.com to get a full-size file)
Calculation of lightning protection for the lumber storage
Calculation of the lightning protection system is made by using the software developed by OAO Krzhizhanovskiy Energy Institute (OAO ENIN).
This software is used in accordance with SO 153-34.21.122-2003, item 3.3.1, and Technical Bulletin No. 25/2009 of the "Roselectromontazh" Association, item 2.
For calculation, the used lightning discharge density to the ground is 4 strikes per sq. m per year.
The results of calculation of the lightning protection performed using software are provided in the table.
| Lightning protection type | 52 x 14 m lightning arresters |
| rotection reliability | 0,88 |
| Number of strikes into the facility, year | 0,24 |
| Number of blowouts into the facility, year | 0,0027 |
| Period of strikes | раз в 4 года |
| Period of blowouts | раз в 37 лет |
We consider that the lightning protection reliability is higher than level 4 according to SO and is very close to level 3 according to SO, which is a good value due to large area of the lumber storage.
Components of the lightning protection system for the lumber storage
Do you have any questions regarding the calculation of the lightning protection and grounding system for a lumber storage? Please contact the ZANDZ Technical Center!
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