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Which type of earthing is done for underground cable?
Plate earthing
Pipe earthing
Coil earthing
Both A and B
Both A and B
Quick Summary: For underground cable systems, earthing is essential to ensure safety and equipment protection by providing a low-impedance path for fault currents. Both plate earthing and pipe earthing are standard industry methods used for providing this grounding connection to the earth's electrode.
For underground cable systems, earthing is essential to ensure safety and equipment protection by providing a low-impedance path for fault currents. Both plate earthing and pipe earthing are standard industry methods used for providing this grounding connection to the earth's electrode.
R=2πLρln(d4L) — Resistance of a pipe electrode of length L and diameter d in soil of resistivity ρ
Earthing works by connecting the non-current carrying metal parts of electrical equipment or cable sheaths to a buried electrode. When a fault occurs, the resistance of the path R=2πrρ is kept low to ensure the fault current flows to the ground, triggering protective devices like fuses or circuit breakers immediately.
Earthing prevents the buildup of dangerous static charges or fault voltages on the cable sheath.
Pipe earthing is generally preferred for underground cables due to higher current-carrying capability and ease of maintenance.
Plate earthing is used where lower soil resistivity is required to achieve a low ground resistance value.
Minimizes step and touch potential for personnel.
Ensures stable operation of protective relaying systems.
Reduces electromagnetic interference in communication circuits near the cable.
High maintenance cost due to corrosion of buried metallic electrodes.
Effectiveness highly dependent on soil moisture and ambient temperature.
Substation cable trench earthing.
Industrial power distribution networks.
Underground transmission line termination points.
| Feature | Plate Earthing | Pipe Earthing |
|---|---|---|
Depth | 1.5 - 3 meters | 3 - 5+ meters |
Coil earthing is a temporary or low-cost method usually not recommended for permanent heavy-duty underground cable installations.
The resistivity of the soil plays a critical role; if high, charcoal and salt layers are added to enhance conductivity.
D is correct — Both plate and pipe earthing are recognized methods for providing a reliable low-resistance connection to earth for underground cable systems.
Always remember that earthing serves two purposes: Equipment Earthing (for safety) and System Earthing (for circuit stability). Both types are vital for underground cable longevity.