Earthing
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Definition
     An object said to be earthed when it is electrically connected by means of an earth electrode. It means connecting the neutral point of the supply system to the general mass of earth by wire electricity might produce by mechanical (A.C.) or chemical (D.C.).
     An earthing electrode shall not be situated within a distance of 1.5 meters from the building whose installation system being earthed.
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“It is not safe to work on equipment which is not earthed”.
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Purpose
- To avoid electric shock to human body.
- To avoid risk of fire due to earth leakage current through unwanted path.
- To ensure that no current carrying conductor rises to a potential with respect to earth than its designed insulation.
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Types of Earthing
- Earthing through a water main system.
- Wire or Strip earthing.
- Pipe earthing.
- Plate earthing.
- Rod earthing.
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Double Earthing
     Double earthing is provided for critical equipment (i.e., transformer, generator, etc.) where the earthing is very much required. When one earth connection is corroded / ineffective then the other earthing provides the connection to earth. The system may underground if one earthing connection is not adequately connected to the system.
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Purpose of Double Earthing:
- When one earthing system fails, then the other one operates.
- Installation of two earthing system reduces the resistance to minimum possible valve.
- Double earthing system provides additional electrical safety to eliminate chances of accidents.
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