Re: Surge / Ground / Lightning

w_tom wrote:
> 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.

Any competent source (including the IEEE guide) along with any competent 
manufacturer will tell you all interconnected equipment needs to be 
connected to the same plug-in suppressor, or interconnecting wires need 
to go through the suppressor. External connections, like phone, also 
need to go through the suppressor. Connecting all wiring through the 
suppressor prevents damaging voltages between wires going to the 
protected equipment.

This is apparently way to complicated for w_ to understand.

For a more detailed explanation, read (starting pdf page 39) the IEEE 
guide titled "Ground potential rise"
http://www.mikeholt.com/files/PDF/LightningGuide_FINALpublishedversion_May051.pdf

The same section explains how plug-in suppressors work.

> 
>   Plug-in protector is not for and does not claim to protect from this
> typically destructive type of surge. 

Complete nonsense. Just another of  w_'s bizarre ideas.

> 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.

The illustration in the IEEE guide has a surge coming in on a cable 
service. There are 2 TVs, one is on a plug-in suppressor. The plug-in 
suppressor protects TV1, connected to it.

The point of the illustration for the IEEE is "to protect TV2, a second 
multi****t protector located at TV2 is required." Apparently a radical 
idea for w_.

w_ says suppressors must only be at the service panel. In this example a 
service panel protector would provide absolutely *NO* protection. The 
problem is the wire connecting the cable entry block to the power 
service 'ground' is too long. The IEEE guide says in that case "the only 
effective way of protecting the equipment is to use a multi****t
protector."

> 
>   What would have avoided above network damage?  Homeowner later
> installed and earthed a 'whole house' protector.

A power service suppressor is a real good idea. It does not protect 
equipment connected to both power and signal wires if there is a high 
voltage between those wires as in the example above. There are other 
hazards that it also misses.

For independent advice read the IEEE or NIST guides. (Both say plug-in 
suppressors are effective).

-- 
bud--