The meaning of the term earthing or grounding is to connect the electrical equipment to the general mass of earth by wire of negligible resistance. This brings the body of the electrical equipment to Zero potential and thus will avoid the shock to the operator. The neutral of the supply system is also solidly earthed to ensure its potential equal to Zero according to Indian Electricity Eale,[?The earthed or connected with earth means connected with the general mass of the earth in such manner as to sure at all times in immediate discharge of energy without danger?.]
DIFFERENCE BETWEEN Neutral AND EARTH WIRE
1) The neutral wire is connected to the neutral point of the transformer, which is earthed only at Sub Station. The earth wire originated from a solid earth at the Sub-Station and is earthed at not less than four equally spaced points during every 1.6 km run of distribution line.
2) By reference to three phase four wire loads for which student may consult any book dealing with Polyphase System it will be realized that the neutral wire carries the return current in the case of single phase load and the out of balance current in the case of unbalanced three phase loads. The earth wire under normal condition does not carry any current. However, If an earth fault occurs the earth wire will carry large current, which will cause, the fuse to blow out thereby protecting life and equipment.
3) Some times when the neutral work is not available or ?broken? one is tempted to connect a single-phase load between a phase wire and the earth wire. This practice can be dangerous because by dowing so the earth wire will assume voltage above earth.
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