Re: Surge / Ground / Lightning

On Sat, 3 May 2008 20:14:17 -0700 (PDT), w_tom <w_tom1@[EMAIL PROTECTED]
> put
finger to keyboard and composed:

>On May 3, 4:38 am, Franc Zabkar <fzab...@[EMAIL PROTECTED]
> wrote:
>> Can you elaborate on this by showing us the path taken by the strike
>> through the TV?
>
>  See many posts that describe this same failure to a network of
>powered off computers.  Surge incoming on wires that typically carry
>most surges into buildings: black (hot) AC wire.  Surge arrived two
>plug-in protectors - each adjacent to powered off computers.  Often
>that surge is trivial; does not overwhelm protection inside a
>computer's power supply.  Maybe - but irrelevant due to the adjacent
>protector.
>
>  Protector did its job - MOVs shunted (connected, diverted) surge
>current into all other AC wires including the green safety ground
>wire.  Green wire connects directly to motherboard and network cards -
>still seeking earth ground.
>
>  Path to earth was through the network and into a third computer.
>Through that third computer's motherboard, through modem, and to earth
>via phone lines.  Semiconductors in these paths were damaged.
>
>  We literally traced this path by replacing ICs.  Some ICs (ie
>network interface chips) even had cracks on packages where surge
>current entered or exiting those ICs.  Absolutely no doubt as to how
>surge currents found earth ground, destructively, via adjacent
>computers.
>
>  Plug-in protector is not for and does not claim to protect from this
>typically destructive type of surge.  Often surges are too trivial to
>overwhelm power supply circuits.  But because that protector was too
>close to powered off computers and too far from earth ground, then
>surge was given an alternative and destructive path to earth ground
>via networked computers.
>
>  Plug-in protectors are for surges that typically don't cause
>damage.  When the essential 'whole house' protector is not earthed,
>then plug-in protectors may earth surges destructively through
>adjacent appliances.  Every time?  Of course not.  But the same
>ineffective protection is demonstrated in Bud's citation - 8000 volts
>destructively on  Page 42 Figure 8.  That surge was permitted inside
>the building.  Plug-in protector did nothing to avert 8000 volts
>destructively via the adjacent TV.  Bud says otherwise by denying Page
>42 Figure 8.
>
>  Page 42 Figure 8 eliminated by properly earthing a 'whole house'
>protector.  Surges that seek earth ground destructively through
>household appliances must be earthed at the service entrance.
>
>  What would have avoided above network damage?  Homeowner later
>installed and earthed a 'whole house' protector.  Solution necessary
>so that plug-in protectors do not earth surges, destructively, though
>adjacent appliances, even on Page 42 Figure 8.  Solution necessary so
>that protection from a typically destructive surge exists.

OK, thanks. That all makes sense. However, I was thinking of a typical
2-pin TV, not an earthed computer.

- Franc Zabkar
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