# 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.

Initial data:

• facility: gas-regulating unit (GRU);

• dimensions: 7 m x 2.5 m x 3 m;

• soil resistivity: 100 Ohm*m.

Задача:

• calculate the lightning protection system;

• calculate the grounding device.

Solution:

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:

м - m

Cone radius according to SO, Table 3.4:

м - m

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

м - m

Ground terminal resistance calculation:

Vertical electrode resistance:

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;

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

Horizontal electrode resistance:

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:

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.

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.

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