Earthing Question

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Earthing system - Wikipedia, the free encyclopedia

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Normal day we are wear the shoe to work , and between shoe, our body and earth is having high resistance .

After work you are going home and take hot bath at the bathroom , during the process the water heater having electric current leak and the fault current pass to your body through ground.

During the bath process our body is wet and the body resistance is low and we don't wear shoe, the fault current will select low resistance path flow through the earth (ground).

Your water heater i.e., all metallic parts are grounded. Therefore you will not have current flowing through your body. The leaking current, if there is any, will directly go to ground.

see this

Earthing system DesignGtou

Grounding System Design

http://electricalnotes.wordpress.com/2012/09/07/difference-between-bonding-grounding-and-earthing/

Myth: Natural earth serves as a return path for fault current.

Fact: Though this may be true in some cases (like in TT Systems), one would be surprised to note that natural earth is a very poor conductor of electric current. Yes! The typical resistivity of the general mass of earth is about 100 Ohm-m. Compare this with the resistivity of Copper, which is, 1.7 x 10^-8 Ohm-m (0.017 Ohm-mm²/m) and that of GI, which is, 1 x 10^-7 Ohm-m (0.1 Ohm-mm²/m).

Definitely, natural earth is much more resistive than Copper or GI. Even the Indian Standard (IS 3043-1987) recognizes this fact. It mentions in its clause 0.3 that 'the earth now rarely serves as a part of the return circuit, but is being used mainly for fixing the voltage of the system neutrals'.

That is why the recent practice is to use a metallic conductor, as the return path for the fault current. This conductor is termed the 'PEN' conductor (in TN-C systems) or the 'PE' conductor (in TN-S systems). The PEN or the PE conductor are earthed at one or many places along its length, only to bring its potential close to the earth potential, which, conventionally is taken as zero (vide Cl. 2.7 of IS 3043).