Re: Surge / Ground / Lightning

In alt.tv.tech.hdtv trader4@[EMAIL PROTECTED]
 wrote:

| And also never heard an explanation from w_  about the inherrent
| conflict in another aspect of his position.  He says appliance/
| electronics manufacturers put surge protection inside the appliance
| and that is peachy keen and appropriate.     Yet he can't explain how
| it is that an MOV inside the electronics actually protects, while an
| MOV located in a plug-in is useless.   Unless there is a magical earth
| ground inside the electronic appliance, it must operate under the same
| conditions as the plug-in.   Geez, that inescapable conflict must give
| w_ nightmares.

Do you know what the acronym for Plug In Surge Suppressor is? :-)

In the case that there is an MOV inside, the MOV in the plug-in unit will
not provide as much _increment_ in benefit.  However, if the appliance is
interconnected with others, then the _increment_ in benefit from a plug-in
unit will be greater as long as the other appliances are connected through
a common plug-in unit.

An MOV can protect against slow rise surges (which are the majority of
events) by means of balancing the voltage difference between any two
wires it is connected to.  When the MOV conducts during such a surge, it
reduces the voltage _difference_ between wires.  Different points inside
the appliance will then all rise in voltage approximately the same.  As
long as that voltage difference is reasonably low, the device is
protected.

Note that devices interconnected to other devices in the case described
above will have issues with the voltage across that interconnection.
If all the interconnected devices are powered through the same plug-in
suppressor, the voltage differences can be more effectively equalized.
In the case of NOT using a common plug-in unit for interconnected devices,
the risk for differences in voltage is at least minimized by using the
same
branch circuit, or even better, the same outlet with a non-protective
power
strip.  As the surge propogates through the building wiring, it is not at
the same voltage potential throughout.

The level of protection provided in this case is greater for lower
frequency
energy, and less for higher frequency energy.  Just how much higher
frequency
energy you get depends on where the lightning hits.  Other protection that
provides a low impedance path to ground will also be more effective
against
low frequency energy.  The further away the lightning strike is, the more
it
loses energy through conductor inductance and alternate paths to ground.
The inductance blocks higher frequency energy while the paths to ground
work
best against the lower frequency energy.

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