Bird Horton posted an update 11 months, 2 weeks ago
Sometimes adding more ground rods and pipes will not do achieve almost anything to bring the soil resistance down in high resistivity areas. Especially sometimes, adding more ground rods will not do anything whatsoever to get the resistance down (the resistance stays the identical).
A fantastic comprehension of soil resistivity and related testing is essential. Some guidelines should be established for the soil testing. Similarly the testing and spacing to ascertain the soil resistivity with depth is very important particularly when deep grounding/earthing elements will be used.
A greater than acceptable ground resistance would impact the safe operation of power system. Several various methods have been used in the past to decrease the grounding resistance in the grounding system. Methods include enlarging the grounding/earthing grid, connecting the primary grounding grid with an external grounding grid, improving the burial depth in the grounding grid, utilizing natural grounding object like steel foundations of structures, adding long vertical grounding electrodes or pipes, and changing the soils round the grounding grid with low resistivity materials and chemicals.
They are compatible with 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. In reality, in a specific soil environment, two or more methods can be considered to lower the grounding resistance effectively.
The method to provide deep vertical grounding electrodes to the grounding grid is very efficient at substations with small area. Using this method can make use of the low-resistivity soil layer and take away the high resistivity soil close to the surface impacted by freezing and occasional temperature. In order to decrease the grounding resistance, the explosive grounding technique was proposed to diminish the grounding resistance of grounding grids in high resistivity area. The look at the explosive grounding technique as with any grounding strategy is also impacted by cost.
One efficient strategy to decrease the earthing resistance of substation is with deep ground wells electrodes. Several kinds of deep ground wells exist: For example it is possible 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 ground well is filled with bentonite material and non-corrosive material to boost resistivity.
To do this sort of grounding you need and also to count on enhanced or higher advanced grounding put in order to calculate correctly the grounding resistance since programs including ETAP or SKM will not have the necessary capacity to do these calculations because the grounding resistance of the equivalent model cannot be easily calculated. The grounding resistance of an deep ground well could be calculated by numerical analysis software package according soil model. The SES software package can be used.
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