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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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What are the reasons for the increase in earthing resistance?
Loose connection
Corrosion between connections
Low moisture in the soil
All of above
All of above
Quick Summary: The resistance of an earthing system depends on soil resistivity, electrode dimensions, and the integrity of the connection. Factors such as loose joints, corrosion, and low soil moisture directly increase the overall contact resistance between the earth electrode and the surrounding soil.
The resistance of an earthing system depends on soil resistivity, electrode dimensions, and the integrity of the connection. Factors such as loose joints, corrosion, and low soil moisture directly increase the overall contact resistance between the earth electrode and the surrounding soil.
R=2πLρln(d4L) — Simplified electrode resistance formula showing direct proportionality to soil resistivity ρ.
The earth electrode resistance is governed by the formula R=2πLρln(d4L). Soil moisture acts as an electrolyte; as it decreases, resistivity (ρ) rises significantly. Furthermore, corrosion and loose connections create high-resistance gaps (contact resistance) at the junctions, impeding the dissipation of fault currents.
Moisture in soil is essential for conductivity; dry soil is an insulator.
Corrosion increases the junction impedance, leading to local heating and higher potential rise during faults.
Loose connections prevent reliable current flow, increasing the voltage drop at the terminal.
Standard Indian earthing resistance (IS 3043) is generally recommended to be low (e.g., < 1 Ω for substations).
Lower resistance ensures faster tripping of protective devices.
Proper grounding protects personnel from step and touch voltages.
High earth resistance leads to 'floating' potentials during fault conditions.
Insufficient moisture levels require frequent chemical treatments or watering.
Electrical Substations
Transmission lines
Industrial machinery grounding
Residential distribution panels
The resistance of an earth electrode is primarily determined by the soil resistivity in the immediate vicinity of the rod.
Chemical treatments (like salt and charcoal) are often used in dry regions to reduce soil resistivity.
D is correct — Loose connections, corrosion, and low soil moisture are all critical physical factors that lead to an undesirable increase in the total earthing resistance.
In exams, if an option is 'All of above' in maintenance questions, check if all factors contribute to the degradation of the system; usually, physical environmental factors and mechanical integrity are both culprits.