When designing cable lines, you should provide for the grounding arrangement for grounding supports of main cable lines. The ZANDZ Technical Centre has received a request to calculate the grounding arrangement for a main cable line. Let's consider what solution was used.
Initial data:
Protected facility: a main cable line.
Estimated section length: 1.5 km.
Support number: 31 pcs.
Soil resistivity: 5,000 Ohm*m.
Task:
To calculate the grounding arrangement to eliminate static discharge, with resistance not exceeding 100 Ohm.
Grounding is made in accordance with the EIC, Rev. 7, Chapter 1.7.
A set of measures to ensure the necessary requirements for the grounding arrangement for the main cable line is represented by the following solutions:
- for one connection point (support): installation of 2 sets of electrolytic grounding ZZ-100-102 connected using a corrosion-resistant steel zinc-plated bar d10 mm. Distance from fencing is 3 m. Deepening is 0.5 m;
- connection to supports is performed every 50 m along the area length, i.e. 31 connection points in total;
- connection to grounding electrodes, connection of bundles and assemblies (wire take-off to supports) is performed using clamp ZZ-005-064.
Calculation of a grounding arrangement resistance for 1 point:
The set ZZ-100-102 resistance:
Ом - Ohm
where C is a dimensionless factor describing the electrolyte concentration in the surrounding soil, 0.125;
ρ – is soil equivalent resistivity, 5,000 Ohm m;
L – is vertical electrode length, 2.4 m;
d – is vertical electrode diameter, 0.065 m;
T – deepening is the distance from the ground surface to the ground electrode, 0.6 m;
Horizontal grounding arrangement resistance:
Гор - Hor Ом - Ohm
where ρ – is soil resistivity, 5,000 Ohm·m;
d - is diameter of the horizontal electrode, 0.01 m;
h - is horizontal grounding depth, 0.5 m;
Lhor – is horizontal electrode length, 5 m.
Electrical impedance of the grounding arrangement:
ЗУ - GA
Ом - Ohm
where n – is a number of sets, vertical grounding arrangements - 2 pcs, horizontal grounding arrangements - 1 pc;
kutil is utilization rate for sets - 0.99; for horizontal grounding arrangement - 0.7;
rated resistance of the grounding arrangement is 82,33 Ohm, which is less than the required value of 100 Ohm.
Кабельная эстакада - Cable tray system
Комплект электролитического заземления - Electrolytic grounding set
Проволока оцинкованная d10 мм - Zinc-plated steel d10 mm
Figure 1. Layout of grounding arrangement components for 1 point.
The list of materials required for two facilities is provided in Table 1.
Table 1. List of required materials.
| № | Part number | Name | Quantity, pcs |
| 1. | ZZ-100-102 | ZANDZ Electrolytic grounding set (horizontal; 3 meters long) | 62 |
| 2. | ZZ-502-010-80 | ZANDZ Zinc-plated steel wire (D 10 mm / S 80 mm²; wire bundle 80 m) | 4 |
| 3. | ZZ-007-030 | ZANDZ Waterproofing tape | 32 |
| 4. | ZZ-005-064 | ZANDZ Conductor connection terminal (up to 40 mm) | 96 |
Do you have any questions about grounding of a main cable line or other facilities? Please, contact the ZANDZ Technical Center!
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