Believe it or not the Earth is the 4th wire.
That is why they call it Ground.
Read more about it here.
http://www.seas.upenn.edu/ese/rca/instruments/misctutorials/Ground/grd.html
Take a look at his site.
http://en.wikipedia.org/wiki/Electric_power_transmission
And this one.
http://www.wipo.int/cgi-pct/guest/getbykey5?KEY=01/69758.010920&ELEMENT_SET=DECL
Here is OSHA's Definitions for Ground.
http://www.osha.gov/SLTC/etools/electric_power/glossary.html
Ground: A large conducting body (such as the earth) used as a common return for an electric circuit and as an arbitrary zero of potential.
Grounded, effectively: Intentionally connected to earth through a ground connection or connections of sufficiently low impedance and having sufficient current-carrying capacity to prevent the buildup of voltages that may result in undue hazards to connect equipment or to persons.
Grounded Conductor: A system or circuit conductor that is intentionally grounded, usually gray or white in color.
Grounding Conductor: A conductor used to connect metal equipment enclosures and/or the system grounded conductor to a grounding electrode, such as the ground wire run to the water pipe at a service; also may be a bare or insulated conductor used to ground motor frames, panel boxes, and other metal equipment enclosures used throughout electrical systems. In most conduit systems, the conduit is used as the ground conductor.
hello hotwaterwiard these switches look wierd ive never seen anything like them , in australia here i dont know what they use but i hear on the news that they are spraying silicon stuff on our powerlines or insulaters may be something to do with dust hazards when it clings to powerlines i geuss and when it rains the dust somehow causes them to catch fire or arc, something like that i think .do you have things like that in the usa.
