5.1.2 - The advantages of earthing
The practice of earthing is widespread,
but not all countries in the world use it.
There is certainly a high cost involved,
so there must be some advantages. In fact
there are two. They are:
1. - The whole electrical system
is tied to the potential of the general mass of earth and
cannot 'float' at another potential. For example, we can
be fairly certain that the neutral of our supply is at,
or near, zero volts (earth potential) and that the phase
conductors of our standard supply differ from earth by 240
volts.
2. - By connecting earth to metalwork
not intended to carry current (an extraneous conductive
part or a an exposed conductive part) by using a protective
conductor, a path is provided for fault current which can
be detected and, if necessary, broken. The path for this
fault current is shown in {Fig 5.2}.
Fig 5.2 Path for earth
fault current (shown by arrows)
|
