How to protect a fire-hazardous storage using catenary wire lightning protection?

Catenary wire lightning rods, according to many, are the most reliable way to protect against lightning. Providing a higher level of protection than rod and mesh lightning rods, catenary wires became a standard of lightning protection at the most important industrial infrastructure facilities. They include such objects as high-voltage transmission lines and tanks farms.

Another important object of the application is a workshop or a shed, in the production process of which explosive and flammable substances are used. In such cases, a ban for the installation of lightning rods directly on the building is an obligatory requirement. As a rule, structures have a gaunt shape. A wire span can be up to 100-150 meters long, so placing the bases on the edges of the building and straining the wire between them, it is possible to observe the condition of the lightning protection according to category 1 of AD 34. After selecting the desired height of the suspended wire, the building will be protected with the required reliability: 0.9, 0.99 up to a maximum desired value of 0.999.

 

 

Lightning protection of a warehouse of paints with the dimensions of 100 x 14 meters and 10 meters high with the reliability of 0.99 is studied in the example.

 

Calculation example

The activities were carried out in accordance with the EIC 7 th ed. Chapter 1.7. of the IS 153-34.21.122-2003 "Instructions for lightning protection of buildings, structures and industrial communications" (hereinafter IS) and AD 34.21.122-87 "Instructions for lightning protection of buildings and structures" (hereinafter AD).
 
Protection of buildings against lightning strikes is carried out by lightning rods. A lightning rod presents itself a device rising above the protected facility to divert the lightning current into the ground without entering the protected facility. It consists of a lightning rod directly perceiving the lightning discharge, down conductor and ground electrode system.

 

Lightning protection

Lightning protection of a building is performed by a catenary wire lightning rod, fixed on two pillars 22 m high, which are installed at the distance of 3 m from the building. Catenary wire span length is equal to 106 m, the rise - 1 m. The building is protected with reliability of 0.99 of the IS.

Grounding

Each catenary wire support requires a grounding device in the form:

1. Laying of a horizontal ground electrode for current spreading in three directions with an angle of 90 degrees between them. The length of each ground electrode is 5 m. The ground electrode is made of copper-bonded stainless steel with the cross-section 4x30 mm (GL-11075), laying depth - 0.5 m.
2. One vertical electrode 3 m long is fixed in each direction at the end of the horizontal ground electrode.
3. Connection of vertical and horizontal electrodes, as well as horizontal electrodes  with a lightning rod is carried out with the help of clamps ZZ-005-064.

 

^{Figure 1 - Layout oflightning protection elements and grounding device (to view in full size, click on the image)}

Calculation of lightning protection:
The following source data are taken for the calculation:

 

1. The density of lightning strikes into the ground - 5,5 strikes / sq. km per year;
2. The number of strikes into an unprotected object - 0.062 1/year, period - once in 16 years.

The results of lightning protection calculation performed by the software, developed by JSC "Energy Institute to the name of Krzhizhanovsky "(JSC" ENIN ") are shown in Table 1.

^{Table 1 - Results of lightning protection calculation}

 

The list of the required materials is given in Table 2:

^{Table 2 - List of materials needs}

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