Bird Persson posted an update 2 months ago
Sometimes adding more ground rods and pipes will not likely do achieve almost anything to bring the soil resistance down in high resistivity areas. Especially sometimes, adding more ground rods is not going to do anything to create the resistance down (the resistance stays the same).
A fantastic knowledge of soil resistivity and related exams are essential. Some guidelines ought to be established for your soil testing. Similarly the testing and spacing to look for the soil resistivity with depth is essential in particular when deep grounding/earthing elements shall be used.
A higher than acceptable ground resistance would affect the safe operation of power system. Several various methods ended up applied to yesteryear to decrease the grounding resistance in the grounding system. Methods include enlarging the grounding/earthing grid, connecting the primary grounding grid by having an external grounding grid, enhancing the burial depth in the grounding grid, utilizing natural grounding object including 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.
They are compatible with different geographical situations however that does not always mean they will work without having a correct soil resistivity testing or proper evaluation and without collection of acceptable data to warrant their application. In fact, within a specific soil environment, several methods can be considered to diminish the grounding resistance effectively.
The method to incorporate deep vertical grounding electrodes on the grounding grid is very great at substations with small area. This technique can utilize low-resistivity soil layer and eliminate the high resistivity soil near the surface suffering from freezing and low temperature. To be able to decrease the grounding resistance, the explosive grounding technique was proposed to lower the grounding resistance of grounding grids in high resistivity area. The evaluation of the explosive grounding technique as with all grounding way is also impacted by cost.
One efficient method to reduce the earthing resistance of substation is by using deep ground wells electrodes. Several kinds of deep ground wells exist: By way of example you’ll be able to drill 150 mm ground well and go 50 meters to 85 meters deep or higher in the earth and soon you reach moist soil ground water or limestone… The floor well is filled with bentonite material and non-corrosive material to improve resistivity.
In order to do this type of grounding you will need also to depend upon enhanced or higher advanced grounding program in to calculate correctly the grounding resistance since programs like ETAP or SKM will not have the required capability to do these calculations as the grounding resistance with the equivalent model cannot be easily calculated. The grounding resistance of an deep ground well can be calculated by numerical analysis software program according soil model. The SES software program can be utilized.
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