Electric Wiring, 3rd Edition

158 Safe and efficient earthing

The neutral conductor is usually connected by the electricity board to earth

electrodes at a number of points along the route (hence the name PME),

particularly when the supply is overhead, and this ensures that the neutral is

earthed even if a break occurs along the route; this factor does not however

directly concern the consumer.

The great advantage of PME is that a metallic path of very low impedance

is provided back to the transformer neutral point, and this means that the

consumer's overload protective devices will normally operate when a phase

to earth fault occurs. Another big advantage is that this pat ...