In electricity supply systems, an
grounding
system defines the electrical potential of the conductors relative
to that of the Earth's conductive surface. The choice of earthing
system has implications for the safety and electromagnetic compatibility
of the power supply. Note that regulations for earthing (grounding)
systems vary considerably between different countries.
A protective earth (PE) connection ensures that all exposed
conductive surfaces are at the same electrical potential as the
surface of the Earth, to avoid the risk of electrical shock if a
person touches a device in which an insulation fault has occurred.
It ensures that in the case of an insulation fault (a "short circuit"),
a very high current flows, which will trigger an over-current protection
device (fuse, circuit breaker) that disconnects the power supply.
A functional earth connection serves a purpose other than
providing protection against electrical shock. In contrast to a
protective earth connection, a functional earth connection may carry
a current during the normal operation of a device. Functional earth
connections may be required by devices such as surge suppression
and electromagnetic-compatibility filters, some types of antennas
and various measurement instruments. Generally the protective earth
is also used as a functional earth, though this requires care in
some situations.
