Velocity Reviews - Computer Hardware Reviews

Velocity Reviews > Newsgroups > Computing > NZ Computing > The shutdown mystery solved? thanks to all

Reply
Thread Tools

The shutdown mystery solved? thanks to all

 
 
w_tom
Guest
Posts: n/a
 
      07-06-2006
The primary function of that wire from meterpanel or mains panel is
human safety. It is earthing. But wire is also enhanced to perform
lightning protection functions. The thickness of that wire (wire
resistance) is sufficient. But wire impedance also must be low. Wire
impedance is lowered by shorter length, no sharp bends, not inside
metallic conduit, etc. These are additional 'functions' applied to
that wire to make wire a better lightning conductor.

Also important is that all incoming utilities connect to same earth
ground - the single point ground. If utilites enter at different
locataions, then one Ohio utility suggests solutions to make those
seperate earthings into single point earthing:
http://www.cinergy.com/surge/ttip08.htm

Mains panel earthing for human safety is also enhanced so that it
serves transistor safety. That earthing wire should be seperated from
other non-earthing wires so that earthed lightning does not induce
transients on those other wires. Just another precaution for making
household earthing more effective - to serve dual functions.

Aluminim siding would provide effective lightning protection if it
was properly earthed AND if it was monolithic. It is not monolithic.
It has poor electrical connections between the interlocked 'clamp
boards'. Points of poor conductivity mean high energy dissipation.
Same applies to any material that conducts lightning. A point of poor
conductivity means voltage rises; more power and more energy dissipates
there. Yes, the aluminum would conduct electricity. But so does wood.
And since wood is not sufficiently conductive, then moisture and
sugars inside that wood heat - may even become explosive.

Lightning rods provide a 'cone of protection'. If the rod is
connected to a superior earth ground, then anything typically beneath
that 60 degree cone is considered protected. Lightning rods don't
atract lightning nor do they discharge the air. Lightning will take
that lightning rod path to earth rather than strike anything below in
that 60 degree cone.

Look at high tension electric lines on tall metal towers. Notice
that little wire highest on the tower. That catenary wire is also
lightning protection. Lightning will strike that catenary wire rather
than strike power wires below. But again, that catenary wire will only
be as good as the earthing of metal tower. Therefore those towers
sometimes have enhanced earthing on their legs. Like lightnng rods,
the catenary wire provides a 'protection cone'. It provides a shorter
electrical path to earth - which is what all lightning protection is
about.

geopelia wrote:
> There is an earthwire that comes out of the house and is fixed on to a
> metal post in the ground. It was put in long before we got the
> computer, I think it is for the radio or TV.
>
> A Lockwood home is sheathed in aluminium. I wonder if that would stop
> lightning.
>
> I've seen lightning hit a Barrage balloon. It looked like that
> Zeppelin, flaming bits coming down everywhere. I think it would have
> earthed itself down the cable. The crew weren't hurt.
> I doubt if anything could stop a strike like that!
>
> Geopelia


 
Reply With Quote
 
 
 
 
Geopelia
Guest
Posts: n/a
 
      07-06-2006

"Matty F" <(E-Mail Removed)> wrote in message
news:e8hgak$tv8$(E-Mail Removed)...
> geopelia wrote:
>
>> There is an earthwire that comes out of the house and is fixed on to a
>> metal post in the ground. It was put in long before we got the
>> computer, I think it is for the radio or TV.

>
> All houses should have an earthwire from the meterboard. It's nothing to
> do with lightning.
>
>> A Lockwood home is sheathed in aluminium. I wonder if that would stop
>> lightning.

>
> It's better than nothing. The conductor from a lightning rod really needs
> to be several cm diameter to be of any use, and to have no sharp bends in
> it. If I could be bothered, I'd run a big cable from my TV aerial to a
> ground post. But there are other houses around much higher than mine so
> I'm not worried.
> In a thunderstorm I sometimes unplug expensive equipment from the wall
> sockets, in case the powerlines in the district are hit by lightning. The
> Skytower can be hit dozens of times in a thunderstorm. It seems to protect
> the CBD quite well.


I don't think the aluminium is meant to stop lightning, it is more for the
protection of the building from other damage. It works well for that.
A huge truck tyre came bounding down the drive once, lost from the road. It
hit the house but only marked the paint a bit.
I can just imagine what would have happened to a weatherboard house, or one
of these new plastered paper ones.
(Or to me, if I had been standing outside!).

Geopelia


 
Reply With Quote
 
 
 
 
Enkidu
Guest
Posts: n/a
 
      07-07-2006
Geopelia wrote:
> "Matty F" <(E-Mail Removed)> wrote in message
> news:e8hgak$tv8$(E-Mail Removed)...
>
>>geopelia wrote:
>>
>>
>>>There is an earthwire that comes out of the house and is fixed on to a
>>>metal post in the ground. It was put in long before we got the
>>>computer, I think it is for the radio or TV.

>>
>>All houses should have an earthwire from the meterboard. It's nothing to
>>do with lightning.
>>
>>
>>>A Lockwood home is sheathed in aluminium. I wonder if that would stop
>>>lightning.

>>
>>It's better than nothing. The conductor from a lightning rod really needs
>>to be several cm diameter to be of any use, and to have no sharp bends in
>>it. If I could be bothered, I'd run a big cable from my TV aerial to a
>>ground post. But there are other houses around much higher than mine so
>>I'm not worried.
>>In a thunderstorm I sometimes unplug expensive equipment from the wall
>>sockets, in case the powerlines in the district are hit by lightning. The
>>Skytower can be hit dozens of times in a thunderstorm. It seems to protect
>>the CBD quite well.

>
>
> I don't think the aluminium is meant to stop lightning, it is more for the
> protection of the building from other damage. It works well for that.
> A huge truck tyre came bounding down the drive once, lost from the road. It
> hit the house but only marked the paint a bit.
> I can just imagine what would have happened to a weatherboard house, or one
> of these new plastered paper ones.
> (Or to me, if I had been standing outside!).
>

I read a story in the paper once about the early days of the motorways
in the UK. Apparently the driver of one of these multi-wheeled
articulated trucks lost a wheel. So the driver (who was with his wife)
slowed down and stopped. It took the best part of a mile apparently.
THey climbed out of the cab and were inspecting the damage when the
wheel came bowling along the road, knocked the poor woman off the verge
and broke her pelvis. I remember it because the woman was supposedly FOAF.

Cheers,

Cliff
 
Reply With Quote
 
 
 
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
script local variables - the root of all mystery? Jason Dusek Ruby 2 09-15-2006 03:30 AM
Cakewalk Pro Audio 9 (running problem) [THANKS] [ MORE THANKS] con't beenthere Computer Support 2 09-07-2006 08:58 AM
Shutdown Error Win XP W/SP2 & All Updates Charlie Evans Computer Support 1 09-24-2005 10:28 PM
Index.dat files, Is it safe to have a program erase *all* of them each shutdown? Edmonton_Guy@usenet.com Computer Support 3 09-20-2005 10:43 AM
Thanks, thanks a lot Rick Computer Support 0 05-05-2004 04:04 AM



Advertisments