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Which type of earthing is done in sandy soil?
Plate earthing
Pipe earthing
Coil earthing
All of above
Pipe earthing
Quick Summary: Pipe earthing is the preferred method for sandy soil because the soil resistivity is very high due to low moisture content. Pipe earthing allows the electrode to be driven deeper into the earth where the soil is more moist and has lower resistance, and it allows for the use of artificial moisture-increasing treatments like charcoal and salt.
Pipe earthing is the preferred method for sandy soil because the soil resistivity is very high due to low moisture content. Pipe earthing allows the electrode to be driven deeper into the earth where the soil is more moist and has lower resistance, and it allows for the use of artificial moisture-increasing treatments like charcoal and salt.
R=2πLρln(d4L) — Resistance of a pipe electrode, where R is in Ω, ρ is soil resistivity in Ω⋅m, L is length in meters, and d is diameter in meters.
ρ=2πSRearth — Wenner's four-pin method to measure soil resistivity.
The soil resistivity (ρ) depends on the moisture content and electrolyte concentration. Sandy soil typically has high resistivity (>1000Ω⋅m). Pipe earthing involves burying a perforated galvanized steel pipe vertically, enabling a deeper penetration to reach lower resistance zones. The addition of salt and charcoal layers around the pipe maintains the soil conductivity by retaining moisture and providing ions for conduction.
Sandy soil has high resistivity due to poor water retention.
Pipe earthing is more effective than plate earthing in sandy regions as it can reach deeper layers.
Salt and charcoal are used to decrease the resistance of the surrounding soil.
The length of the pipe electrode should be at least 2.5 meters to ensure adequate surface contact.
Effective in areas where surface soil is dry.
Easier to maintain and treat with chemicals.
Higher surface area contact than rod earthing.
Requires significant depth excavation.
Pipe is subject to corrosion over time.
Not suitable for rocky terrain.
Residential and small industrial building electrical installations.
Power transmission line towers in high-resistivity soil.
Transformer substations in arid areas.
| Feature | Plate Earthing | Pipe Earthing |
|---|---|---|
Depth Capacity | Limited (usually 1.5-2m) | Deep (2.5m+) |
Ideal Terrain | Clay/Moist soil | Sandy/High-Resistivity soil |
IS:3043 is the standard code of practice for earthing installations in India.
Plate earthing is generally used in moist soil because it requires a larger surface area to achieve low resistance.
B is correct — Pipe earthing is preferred in sandy soil because it can be installed at greater depths to access moist, lower-resistivity earth.
In competitive exams, remember that Pipe Earthing is the 'all-rounder' for most standard applications, while Plate Earthing is strictly for moist soil/large fault current areas.