There is usual electrical design standards for earthing system design such as BS7340, IEEE std. 80&81.SOIL Resistivity is the important factor in deciding the earthing connection type. Depending on the earthing arrangement there is a total of 5earthing system. In TN S, separate protective earth and neutral conductor is running throughout the system and interconnecting only near the source. Best methods used in recent installations is TN c s method wherein protective earth and neutral conductors is running through the same conductor but separate neutral earth lines been followed for indoor wiring and flexible cable connections. TN C method is initial development prior to TN C S wherein even in indoor and flexible connections same core is used. Earlier methods and even followed in smaller constructions like home, shops in part of the world now as well is TT earthing wherein earth cable is not laid between the source and distribution line but both are independently earthed. In IT earthing there is no earthing connecrion at all.
