Join 60,000+ competitive exam aspirants
or with email
Your Cart
SubtotalтВ╣0
TotalтВ╣0
Examoogle тАв User тАв info@examoogle.com тАв EE-2024-8821
Chapter 1 of 12 тАв Page 1 of 248ЁЯФТ Protected PDF тАв Watermarked
Join 60,000+ competitive exam aspirants
According to Indian Standard Resistance between any part and Earth is
1K Ohm
100 Ohm
1 Ohm
Can't say
1 Ohm
According to the Indian Standards (IS 3043: Code of Practice for Earthing), the earth resistance for a small installation or individual earthing electrode is recommended to be maintained at a very low value, typically not exceeding 1 Ohm, to ensure effective dissipation of fault currents and personnel safety.
According to the Indian Standards (IS 3043: Code of Practice for Earthing), the earth resistance for a small installation or individual earthing electrode is recommended to be maintained at a very low value, typically not exceeding 1 Ohm, to ensure effective dissipation of fault currents and personnel safety.
VtouchтАЛ=IfтАЛ├ЧRearthтАЛ тАФ Represents the touch voltage developed during a fault condition where RearthтАЛ is the resistance to ground.
R=╧БALтАЛ тАФ Defines the resistance of the electrode material where ╧Б is resistivity, L is length, and A is cross-sectional area.
The principle of electrical earthing is to provide a low-impedance path to the ground for fault currents. If the resistance R is kept low (тЙд1╬й), the voltage rise on the metal enclosure of equipment during a fault (V=I├ЧR) is restricted to a safe level, preventing electric shock and allowing protection devices like ELCBs or MCBs to trip rapidly.
Lower earth resistance significantly improves the reliability of protective relaying systems.
Soil resistivity varies with moisture content, temperature, and salt content, affecting the electrode resistance.
Multiple electrodes in parallel are often used to achieve the desired <1╬й target.
Standard IS 3043 is the definitive guide for earthing practices in India.
Minimizes step and touch potentials during faults.
Protects sensitive electronic equipment from transient surges.
Ensures consistent reference potential for electrical systems.
Achieving low resistance in rocky or dry soil is expensive.
Corrosion of electrodes over time increases resistance.
Domestic electrical installations.
Industrial substation earthing grids.
Lightning protection systems.
In large industrial substations, the overall grid resistance may be much lower than 1 Ohm, often reaching 0.5 Ohm or less.
Values like 100 Ohms are generally considered high and indicate an ineffective ground connection, likely leading to a failure in operating protection devices during a ground fault.
C is correct тАФ As per Indian Standard specifications for effective earthing, the resistance between any part of an installation and the earth should be 1 Ohm or less to ensure safety.
Always remember that earthing resistance is inversely proportional to the effectiveness of the protection system; a lower value is always preferred for safety.