How to reduce earth resistance and which methods are help to reduce earth resistance ?

The maximum value beyond which the earth electrode resistance should not be increased is 1.5Ω. However for better performance at power house, at substation its value should be 0.5Ω and 1.0Ω respectively. It can be achieved by applying following.

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Soldering Nuts and Bolts : The earth resistance can be reduced soldering the nuts and bolts of the earth electrode instead of simply lightening.
By pouring water : In the summer season the dampness around the earth electrode considerably decreases which increases the resistance of the earth electrode. For increasing the moisture three to four buckets of water mixed with salt are poured down in the funnel every few days to keep soil moist around the electrode.
Increasing in Plate Area : By increasing the area of the plate, the resistance will decrease but the decrease in resistance is extremely small. Therefore this method is not practicable.
By Power Charcoal and Salt : Salt and charcoal is mixed in the ratio of 1 : 5 respectively and added around the earth electrode. This reduces the contact area of the plate as well as provides moisture around the electrode, thereby reducing the earth resistance.
Depth of Plate : If the same plate is buried deep in the earth, it reduces the resistance of the earthing system up to a certain limit. No doubt this value is also very small but it helps to great extent.
Installation of Parallel Electrode : The installation of a number of earth electrodes in parallel for the same depth decreases the earth resistance to a great extent. This system requires greater area of soil and therefore it is suitable where sufficient open soil is available for earthing. In this system all the earth plates are connected in parallel for reducing the overall earth resistance. This method is adopted for all big power house and sub-station where the earth resistance has to be reduced to a great extent.

The methods mentioned above have their own limitations but the common method is that the area around the earthing pipe or earth electrode is increased and charcoal soaked in salt, water is filled in the pit. In dry season, the fresh salt water is poured into the earth though the pipe. This is done to increase moisture level within the earth pit and this way earth resistance shall be considerably reduced.

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