altohour92 posted an update 9 months, 1 week ago
Sometimes adding more ground rods and pipes is not going to do achieve something to bring the bottom resistance down in high resistivity areas. Especially sometimes, adding more ground rods will not likely do just about anything to take the resistance down (the resistance stays the identical).
An excellent knowledge of soil resistivity and related testing is vitally important. Some guidelines must be established to the soil testing. Similarly the testing and spacing to discover the soil resistivity with depth is vital especially if deep grounding/earthing elements will probably be used.
A higher than acceptable ground resistance would get a new safe operation of power system. Several various methods had been applied to yesteryear to lower the grounding resistance in 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 with the grounding grid, utilizing natural grounding object like 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 does not mean they’ll work with no correct soil resistivity testing or proper evaluation and without assortment of acceptable data to warrant their application. In fact, in the specific soil environment, several methods can be considered to diminish the grounding resistance effectively.
The method to add deep vertical grounding electrodes on the grounding grid is quite effective in substations with small area. This method can utilize low-resistivity soil layer and eliminate the high resistivity soil close to the surface afflicted with freezing and low temperature. As a way to slow up the grounding resistance, the explosive grounding technique was proposed to decrease the grounding resistance of grounding grids in high resistivity area. The look at the explosive grounding technique as with all grounding method is also suffering from 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 more on your lawn before you reach moist soil ground water or limestone… The ground well is filled with bentonite material and non-corrosive material to improve resistivity.
To carry out such a grounding you will need and to count on enhanced or higher advanced grounding put in order to calculate correctly the grounding resistance since programs such as ETAP or SKM will not have the specified chance to do these calculations for the reason that 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 program works extremely well.
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