A water tower seems to be a facility that, from the first sight, is not necessary to protect against lightning. The lightning protection is required not to protect the tower itself but to protect the equipment in the pumping room, with which a metal coupling exists along pipes or through the water. If a water tower is not protected against lightning, then the lightning current will go to the pumps along the pipeline and cause their failure.
To provide lightning protection of the water tower, 4 x 7 m lightning rods are used. Reliable grounding of current collectors from lightning arresters allows flowing of the main lightning current in the ground, which significantly reduces the current fraction that may go along pipelines.
Let's consider the lightning protection for the water tower in more details.
Task
To calculate the lightning protection for the water tower.
Solution
Calculations of the lightning protection system for the water tower are made in conformity with the following regulatory documents:
- "Electrical Installations Code" (hereinafter referred to as 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 referred to as SO).
- "Instructions for mounting the lightning protection of buildings and structures" RD 34.21.122-87 (hereinafter referred to as 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 water tower 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 water tower
A set of arrangements ensuring compliance with the lightning protection requirements is based on the following solutions:
- Installation of 4 lightning rods 7 m high is carried out by attachment to the wall. It is taken into account that 1.5 m of the height of interception rods are necessary for mounting
- Lightning arresters are interconnected to arrange two current collectors using galvanized steel wire D = 8 mm from each lightning arrester. The main conductor cables are mounted (with mounting step 0.6-1 m):
- to the walls using clamps GL-11703A.
- Connection and branching of current collectors are made using clamps GL-11551A.
A set of measures to ensure the requirements for the grounding arrangement is based on the following solutions:
- Installation of a grounding arrangement consisting of a horizontal electrode (steel zinc-plated bar with a cross-section 4 x 30 mm), depth 0.5 meter laid along the structural perimeter at the distance of 1 m from the foundation, and 4 vertical electrodes (rods made of copper-plated steel with the diameter of 14 mm) 3 m long.
- The interconnection of vertical and horizontal electrodes is carried out using clamps ZZ-005-064.
- The connection of the current collector with the output of the galvanized ground bar is performed using control clamps 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 protection zone provides the reliability equal to 0.9 SO.
Figure 1. Layout of elements of the lightning protection and grounding arrangement for the water tower.
Условные обозначения - Key
Стержневой молниеприемник - Lightning rod
Горизонтальный заземлитель - Horizontal grounding electrode
Вертикальный заземлитель длиной 3 м - Vertical grounding electrode 3 m long
Токоотвод - Current collector
Зажим для подключения проводника - Clamp for conductor connection
Зажим для соединения токоотводов - Clamp for current collector connection
Зажим контрольный (проволока+полоса) - Control clamp (wire + bar)
Зона защиты на отм. - Protection zone at mark
С надежностью 0,9 СО - with the reliability of 0.9 according to SO
Components of the lightning protection system for the water tower
Do you have any questions relating to calculation of the lightning protection and grounding of the water tower? Please, contact the ZANDZ Technical Center!
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