Sometimes adding more ground rods and pipes is not going to do achieve something to bring the ground resistance down in high resistivity areas. Especially sometimes, adding more ground rods will not a single thing to take the resistance down (the resistance stays the identical).
A great idea of soil resistivity and related tests are very important. Some guidelines should be established for your soil testing. Similarly the testing and spacing to determine the soil resistivity with depth is important in particular when deep grounding/earthing elements are going to be used.
A higher than acceptable ground resistance would impact the safe operation of power system. Several various methods ended up applied in days gone by to decrease the grounding resistance of the grounding system. Methods include enlarging the grounding/earthing grid, connecting the key grounding grid by having an external grounding grid, enhancing the burial depth of the grounding grid, utilizing natural grounding object such as steel foundations of structures, adding long vertical grounding electrodes or pipes, and changing the soils throughout the grounding grid with low resistivity materials and chemicals.
These techniques are suitable for different geographical situations however that doesn’t imply they’re going to work without having a correct soil resistivity testing or proper evaluation and without assortment of acceptable data to justify their application. Actually, inside a specific soil environment, two or more methods can be considered to decrease the grounding resistance effectively.
The technique to provide deep vertical grounding electrodes on the grounding grid is extremely good at substations with small area. This process can utilize the low-resistivity soil layer and take away the high resistivity soil near the surface afflicted with freezing and low temperature. In order to limit the grounding resistance, the explosive grounding technique was proposed to lower the grounding resistance of grounding grids in high resistivity area. The look at the explosive grounding technique as with every grounding method is also afflicted with cost.
One efficient way to slow up the earthing resistance of substation is by using deep ground wells electrodes. Several kinds of deep ground wells exist: For instance you can drill 150 mm ground well and go 50 meters to 85 meters deep or even more in your yard before you reach moist soil ground water or limestone… The soil well is stuffed with bentonite material and non-corrosive material to improve resistivity.
To do this sort of grounding you will need and also to depend upon enhanced or higher advanced grounding program in order to calculate correctly the grounding resistance since programs like ETAP or SKM will not have the specified capability to do these calculations since the grounding resistance of the equivalent model cannot be easily calculated. The grounding resistance of your deep ground well may be calculated by numerical analysis program according soil model. The SES software program can be used.
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