The ZANDZ Technical Centre sometimes receives requests to calculate lightning protection and grounding systems for very exciting or even exotic facilities. One of such requests was aimed at providing grounding for an administrative building at NPP in Bangladesh. The customer's requirements were rather strict: to provide grounding resistance of 4 Ohm in the 10 x 10 m area and with a high-resistivity soil, 1,500 Ohm*m.
The soil is found to be suitable for electrolytic grounding. Therefore, 9 m vertical electrolytic electrodes were used. They allow obtaining the lowest grounding resistance within a limited area. As a result, by using only five electrolytic sets ZZ-100-102-9MB we could obtain the grounding resistance for NPP in Bangladesh at 4 Ohm.
Read more to see the details of the calculation of the grounding system for the administrative building at NPP in Bangladesh.
Task
To calculate the grounding system for the administrative building at NPP in Bangladesh.
Solution
Solutions for grounding NPP were made in accordance with the Electrical Installations Code, Rev. 7.
Description of the grounding system for NPP in Bangladesh
- To provide rated resistance of the grounding arrangement, electrolytic grounding ZANDZ ZZ-100-102-9MB is proposed.
- Five sets of electrolytic grounding ZANDZ ZZ-100-102 are installed to be combined by a horizontal grounding arrangement made of a corrosion-resistance steel copper-plated bar with the cross-section of 4 x 30 mmGL-11075).
- The sets are installed at the distance at least 6 meters with parallel installation to provide suitable utilization ratio and optimal electrolyte distribution volume in the soil.
- Clamps ZZ-005-064 are used to connect grounding electrodes.
Условные обозначения - Legend
- горизонтальный заземлитель - horizontal grounding electrode
- комплект электролитического заземления - electrolytic grounding set
- зажим для подключения проводников - clamp for connecting wires
Figure 1. Grounding plan for the administrative building at NPP in Bangladesh.
Calculation of a grounding arrangement resistance
Based on the customer's data, the estimated soil resistivity is 1,500 Ohm∙m.
Warning. In case the Customer provided erroneous and limited soil data, the above calculation of a grounding arrangement is considered incorrect. If the soil resistivity differs from the calculated one, it is necessary to perform computations with a real value. If the normalized impedance of the grounding arrangement is exceeded, there must be introduced the design corrections.
Electrical impedance of the grounding arrangement:
Ом - Ohm
Гор - Hor
ЗУ - GA
The estimated resistance of the grounding arrangement is 3.73 Ohm, which is less than the required value of 4 Ohm.
Supplies for the grounding system for NPP in Bangladesh
|
Item # |
Part number |
Product |
Amount |
|
1. |
ZZ-100-102-9МВ |
5 |
|
|
2. |
GL-11075-50 |
GALMAR Copper-plated strip (30 * 4 mm / S 120 mm²; 50-meter strip bundle) |
1 |
|
3. |
GL-11075-10 |
GALMAR Copper-plated strip (30 x 4 mm/S 120 mm²; 10-meter strip bundle) |
1 |
|
4. |
ZZ-005-064 |
9 |
|
|
5. |
ZZ-007-030 |
3 |
Do you have any questions for the administrative building grounding at NPP in Bangladesh? Contact the ZANDZ Technical Centre!
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