Indian Standards : Important Points

National Electrical Code 2011 (First Revision). SP 30:2011. Bureau of Indian Standards.


3.0.9 It is recommended that the value of any earth system resistance shall not be more than 5.0, unless otherwise specified.

IS: 3043 – 1987 (Reaffirmed 2001). Indian Standard CODE OF PRACTICE FOR EARTHING. (First Revision). Second Reprint February 1998. UDC 621.316.99.006.76.


  1. Eathing in power stations and sub stations.

20.1To minimize risk of damage to certain auxiliary plant, the rise of potential of a station earthing installation above the potential of true or remote earth should be as low as practicable.

20.1 There is advantage in using a common earth where the earth electrode resistance of any bonded metalwork etc, to earth is 1W or less, as is usual at power stations, large outdoor substations or substations.

20.2 Resistance of 5 to 50 W is sometimes the minimum economically possible.


SECTION 7: Medical Establishment

Table 10: Safety provisions:  (Clause 24.1.1)

Provisions          Principle requirement

P2                          Resistance between extraneous conductive parts and the
Protective conductor busbar of the rooms not exceeding 0.1Ω

 SECTION 9: Miscellaneous installation and Consideration

31. Mines & Quarries

31.2 Power System Earthing.

If the supply transformer (or generator) is distant from the consumer’s premises provision of an earth terminal at the premises should be requested. Where this is possible, the earth terminal should be made available by means of an additional earth conductor in the supply cable or overhead line. If the provision of such an earth terminal is impracticable then it is imperative that the earth electrode at the supply source and consumer premises is maintained such that their resistance to the general mass of earth is as low as possible for example less than 2W.


32. Street lighting and other electrically supplied street furniture.

32.5 In the case of circuits feeding more than one item of street furniture, for example by looping an earth electrode should be installed at the last or penultimate unit and this electrode should be such as to make the resistance to earth of the neutral at any point less than 20W before the connection of any circuit protective as bonding conductor to the neutral terminal.

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