Walsh Wentworth posted an update 1 year, 4 months ago
Sometimes adding more ground rods and pipes will not do achieve anything to bring the soil resistance down in high resistivity areas. Especially sometimes, adding more ground rods won’t do anything to take the resistance down (the resistance stays the same).
A fantastic idea of soil resistivity and related tests are essential. Some guidelines ought to be established for that soil testing. Similarly the testing and spacing to determine the soil resistivity with depth is vital particularly when deep grounding/earthing elements are going to be used.
A greater than acceptable ground resistance would get a new safe operation of power system. Several various methods have been applied in days gone by to lower the grounding resistance of the grounding system. Methods include enlarging the grounding/earthing grid, connecting the key grounding grid with the external grounding grid, improving the burial depth from 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 compatible with different geographical situations but that doesn’t imply they’ll work with no correct soil resistivity testing or proper evaluation and without collection of acceptable data to warrant their application. Actually, in a specific soil environment, 2 or more methods can be considered to decrease the grounding resistance effectively.
The process to incorporate deep vertical grounding electrodes towards the grounding grid is very great at substations with small area. This technique can utilize low-resistivity soil layer and take away the high resistivity soil nearby the surface impacted by freezing and low temperature. In order to limit the grounding resistance, the explosive grounding technique was proposed to diminish the grounding resistance of grounding grids in high resistivity area. The evaluation of the explosive grounding technique as with all grounding way is also affected by cost.
One efficient strategy to slow up the earthing resistance of substation is with deep ground wells electrodes. Several types of deep ground wells exist: For example you’ll be able to drill 150 mm ground well and go 50 meters to 85 meters deep or higher in the ground before you reach moist soil ground water or limestone… The ground well is filled with bentonite material and non-corrosive material to enhance resistivity.
In order to do this kind of grounding you may need and to rely on enhanced or more advanced grounding enter in to calculate correctly the grounding resistance since programs like ETAP or SKM would not have the necessary capacity to do these calculations because the grounding resistance with the equivalent model cannot be easily calculated. The grounding resistance of your deep ground well may be calculated by numerical analysis application according soil model. The SES software package can be used.
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