I'm an ET, not an EE, but I'll take a stab at this;

Joan Rapier wrote:
> [1]Why is it important to have (earth) ground connected to one's
> computer or any appliance, equipment, etc. that has
> three-pronged AC plugs?

Any voltage measurement is in respect to another point in the
circuit. The earth conducts electricity somewhat, so it was
decided long ago, (in USA anyway), to use earth as a reference
and common, (ground) connection. All power transmission is
grounded periodically to earth. And electricians like to know
the potential of the line they are working on with respect to the
ground they may be standing on! Anyway, it was later decided that
it would be nice if all electrical appliances had their metal
cases connected to earth ground, so that any short circuits to the
case would not cause the user to be electrocuted, (when touching
the object while standing on earth), and would blow the fuse
instead. This was and is a very good idea. That's where the third
prong came along.
I wish I could provide a URL with this better explained.

> [2]Is it the case that earth ground plays an integral role in the
> engineering and function of any surge suppressor, UPS, or line
> conditioner?
I'm not sure but would think, yes; UPS's and line conditioners
will constantly compare voltages between the three legs of the
line and make corrections as necessary. Surge supressors will
likely only send the surge to ground only after it reaches a
certain high level (and it will likely be too late).

> [3]If someone is moving into a home whose outlets are not grounded (to
> do so would be very costly as the concrete foundation is not raised),
> how might they protect their sensitive electronic equipment like
> computers and peripherals?
I'm not sure that US code allows wiring in the slab. All I have
seen is in attic and walls. Anyway, if only two wire system to
each outlet, simply install three-wire outlets where the sensitive
equipment is to be used, connecting the ground wire to a copper-clad
rod driven about 3 feet(?) into the ground outside the house. The
electrical service to the house will likely have the necessary rod.
  (in my situation, a rental with faulty wiring, I can feel the
electrical "tension" on my computer case when standing on the
carpeted concrete slab by the computer in stocking feet. Would
likely give me a big shock if the floor were wet! This indicates
to me a bad ground. But my computers have worked just fine with
this for three years).
  You may get by with three-prong to two-prong (with ground
lead) adapters for a short time, but I would recommend against
it. They tend to be not grounded and become permanant.

> [4]In the case of number [3], is using GFI outlets their only
> option?
I don't know anything about ground fault interrupt...
somebody help me.

> [5]Can one assume that, if an appliance, computer, etc. has a
> three-pronged outlet that its circuitry is designed to exploit
> the advantages of earth ground in the event of over-current
> or over-voltage?
NO! It's only for shorts, (and radio frequency interference).
One needs UPS and/or line conditioners for those faults.

HTH
Larry Hooper

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