Lightning Protection of a Gas-Regulating Unit in the Moscow Region

The ZANDZ Technical Center has received a request to calculate the lightning protection and grounding system for a gas-regulating unit (GRU) in the Moscow Region. Let us further consider a solution proposed by our specialists.

Lightning protection and grounding for a GRU

Initial data:

  • facility: gas-regulating unit (GRU);

  • dimensions: 7 m x 2.5 m x 3 m;

  • soil resistivity: 100 Ohm*m.



  • calculate the lightning protection system;

  • calculate the grounding device.




Lightning protection and grounding of the building are made in accordance with:


The facility is "special, environmentally hazardous" from the viewpoint of SO and is classified as Category II of the lightning protection according to RD.


A set of measures to meet the necessary requirements to the lightning protection system and to the grounding arrangement of the GRU includes the following solutions:

  1. Lightning protection of the facility is made using a 20 m lightning rod.

  2. The space R = 5 m, H = 2.5 m above breathing tubes of the GRU is additionally protected.

  3. Copper-plated steel electrodes 3 m long in the locations of the current collector downdrops are used as vertical ground electrodes. The copper-plated steel strip with a cross-section of 30 x 4 mm, combining all vertical electrodes, is used as a horizontal ground electrode. The distance to the facility foundation is at least 1 m. Strip deepening is 0.5 to 0.7 m.

  4. According to EIC-7 issue, par.1.7.55, Grounding devices for protective grounding of electrical installations for buildings and structures and the 2nd and 3rd categories lightning protection of these buildings and structures, as a rule, shall be common.

  5. Resistance design value of the grounding device is 3.72 Ohm.

  6. If there are concrete-steel constructions, they shall be connected to down conductors/grounding device.

  7. Connection to the grounding device is carried out using ZZ-005-064 clamps.


The results of calculation of protection zones according to SO:

h = 20 m;

Cone height according to SO, Table 3.4:

Protection radius cone height

м - m

Cone radius according to SO, Table 3.4:

Protection zone cone radius

м - m

For the protection zone with the required reliability, radius rx at the height of hx = 5.5 m is defined as follows:

Protection zone at the required elevation


м - m

Ground terminal resistance calculation:

Vertical electrode resistance:

Vertical grounding electrode calculation

Ом - Ohm
Верт - Vert
Экв - Eqv

where    ρρeq – is equivalent soil resistivity, 100 Ohm·m;

L – is vertical electrode length, 3 m;

d – is vertical electrode diameter, 0,014 m;

T – is depth, i.e. the distance from the ground surface to the ground electrode, 2 m;

Grounding electrode depth

where     t  – is deepening of the top of the electrode, 0.5 m.


Horizontal electrode resistance:

Horizontal grounding electrode calculation

Ом - Ohm

where    ρ – is soil resistivity, 100 Ohm·m;

b - is horizontal electrode width, 0.03 m;

h - is horizontal electrode depth, 0.7 m;

Lhor is horizontal electrode length, 54 m.


Electrical impedance of the grounding arrangement:

Grounding arrangement impedance

Ом - Ohm

where n – is a number of sets, vertical grounding arrangements - 3 pcs, horizontal grounding arrangement - 1 pc;

Kutil – is utilization rate, 0.75.

The calculated resistance of the grounding arrangement is 3,72 Ohm.


The location of the equipment is shown in Figure 1.

Lightning protection and grounding for the GRU

Figure 1. Equipment layout.


ГРПБ - GRU Условные обозначения - Legend

The list of necessary materials is given in Table 1.


Table 1. List of needed materials.

Part number Name Quantity, pcs Unit weight, kg. Note
1. ZZ-201-020 ZANDZ 20 m vertical lightning arrester (zinc-plated steel; with parts embedded under the foundation) 1    
2. GL-11075-50 GALMAR Copper-plated strip (30 * 4 mm / S 120 mm²; 50-meter strip bundle) 1 0,98 В метрах
3. GL-11075-20 GALMAR Copper-plated strip (30 * 4 mm/ S 120 mm²; 20-meter strip bundle) 1 0,98 В метрах
4. ZZ-001-065 ZANDZ Copper-plated threaded grounding rod (D14; 1,5 m) 6 2,00  
5. ZZ-002-061 ZANDZ Threaded coupling 4 0,08  
6. ZZ-003-061 ZANDZ Termination 3 0,07  
7. ZZ-004-060 ZANDZ Guide head for jackhammer attachment 2 0,09  
8. ZZ-005-064 ZANDZ Conductor connection terminal (up to 40 mm) 6 0,312  
9. ZZ-006-000 ZANDZ Conductive grease 1 0,10  
10. ZZ-007-030 ZANDZ Waterproofing tape 2 0,40  
11. ZZ-008-000 ZANDZ Attachment to the hammer (SDS max) 1 0,50  

Do you have any questions regarding lightning protection and grounding of the GRU? Please contact the ZANDZ Technical Center.

Related Articles: