mexicobangle79 posted an update 11 months, 1 week ago
Sometimes adding more ground rods and pipes won’t do achieve everything to bring the bottom resistance down in high resistivity areas. Especially sometimes, adding more ground rods will not likely do anything to get the resistance down (the resistance stays precisely the same).
A fantastic knowledge of soil resistivity and related exams are extremely important. Some guidelines needs to be established for that soil testing. Similarly the testing and spacing to ascertain the soil resistivity with depth is vital especially if deep grounding/earthing elements shall be used.
A higher than acceptable ground resistance would impact the safe operation of power system. Several various methods have been utilized for days gone by to diminish the grounding resistance in the grounding system. Methods include enlarging the grounding/earthing grid, connecting the main grounding grid with an external grounding grid, enhancing the burial depth with the grounding grid, utilizing natural grounding object for example steel foundations of structures, adding long vertical grounding electrodes or pipes, and changing the soils across the grounding grid with low resistivity materials and chemicals.
They are suitable for different geographical situations but that does not mean they are going to work without a correct soil resistivity testing or proper evaluation and without assortment of acceptable data to justify their application. The truth is, in a specific soil environment, 2 or more methods can be viewed as to decrease the grounding resistance effectively.
The process to incorporate deep vertical grounding electrodes for the grounding grid is extremely great at substations with small area. This method can utilize low-resistivity soil layer and eliminate the high resistivity soil at the surface suffering from freezing and low temperature. To be able to reduce 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 any grounding method is also affected by cost.
One efficient way to limit the earthing resistance of substation is to apply deep ground wells electrodes. Several types of deep ground wells exist: For instance you are able to drill 150 mm ground well and go 50 meters to 85 meters deep or higher in the earth unless you reach moist soil ground water or limestone… The floor well is loaded with bentonite material and non-corrosive material to further improve resistivity.
To do this kind of grounding you may need also to count on enhanced or maybe more advanced grounding program in order to calculate correctly the grounding resistance since programs like ETAP or SKM do not have the required chance to do these calculations because the grounding resistance from the equivalent model can’t be easily calculated. The grounding resistance of the deep ground well could be calculated by numerical analysis program according soil model. The SES software package works extremely well.
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