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Dial up modem problem



 
 
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  #1  
Old September 8th 03, 08:28 AM
Richard Freeman
external usenet poster
 
Posts: n/a
Default Dial up modem problem


"w_tom" wrote in message
...
This is deception:
I like to tell callers that the modem has acted as a fuse,
and saved the rest of their P.C.

Lightning has traveled many miles through non-conductive
air. Is a silly little 'fuse' going to stop what miles of air
did not? Of course not. But basic technology also says a
fuse (response time 10 milliseconds) cannot possibly protect
from a surge (typically 100 microseconds). No fuse is
installed to provide such protection - as demonstrated twice
over.

First, surge passed through modem's off-hook relay circuit


You are starting to grasp the concept then .

and other components including motherboard ground plane.


well since we are being pedantic here try "heading for the Ground plane"

Only
then does something fail; typically a modem off-hook relay.


built in surge arrestors, Input and Output op-amps, Modem processor, Modem
PSU etc etc etc

Typical reason for so many computer peripherals damaged -
surge entered on AC electric and exited to earth ground via
other paths.


Damn just when I thought w_tom had grasped the concept. Once again w_tom
goes on with his fantasy that Lightning comes in via AC mains and exits via
the phone Line.

Lets see now applying a little bit of Basic Physics and electrical Theory we
have two Lines:

Phone Line:
No earth on either leg of the cable in fact a very high impedance path to
earth via the phone line maybe several kms away.
thin relatively high impedance wire with a DC resistance alone running to
tens of Ohms (which is why exchange damage is less common - but still
occours)

AC Mains:
typically runs multiple earthed Neutral that is multiple Earth points (in my
street about every 25 metres or so)
Relativily thick low impedance often multi strand cabling a fraction of an
ohm in impedance and with even the Active to Neutral path (via the
Transformer) giving a nice low impedance path to earth.

hmmmm no prizes for guessing which is the better path to earth here folks !

No damage can occur without both incoming and
outgoing path.


yep !

One traditional path that causes "No Dialtone
Detected" message is incoming on AC electric and outgoing on
phone line to earth ground.


BS! incoming Lightning coming in via the phone line blowing the living *^&t
out of the modem on the way through and exiting the far superior earth on
the AC mains

Damage that has often been
demonstrated by replacing off-hook PNP transistor; making
modem work again.


In the event of a distant strike maybe if you are lucky (but lets face it
who fixes modems nowadays ?)
in the event of a near or direct strike ... Forget it your modem is toast.

Surge damage is traceable to wires that entered building
without a connection to central earth ground. Modem never
acts like a fuse nor protected anything. That surge, as
taught in primary school science, first must have passed
through everything in a complete electric circuit. Many
forget primary school science when rationalizing about surge
damage. Many say the surge entered on phone line, damaged
modem and stopped -


Well almost more like Lightning entered modem via phone line and found nice
alternative paths to earth via AC mains - also via your PC motherboard if
you have an internal modem. But to all intents and purposes since it was
safely shunted to (mains) earth at this point and if it did no further
damage. it effectively dissapeared from the users view at this point.

a direct violation of primary school
science. It is that simple. Modem was damaged because surge
first took a complete circuit path through that computer - and
only then damaged something.


well if you are being a pedant it took a complete circuit path through that
computer and fried it en route.


Richard Unsworth wrote:
All I know is that many people I have spoken to while answering

technical
support lines have suffered blown modems due to a nearby lightning

storm.
eg. 1. It worked and connected 2. There was thunder and lightning nearby

3.
It says 'No dial tone'.
And this happened to my pc - I heard just one spectacular bang the April
before last - I was about a mile and a half from home. The next day I
switched on the pc - dead. Nothing. Having left my diagnostic brain at

work,
it didn't dawn on me until a local child said 'Have you seen where the
lightning blew the paving stone into the road?' This was sixty yards

down my
street.


Yep thats classified as a near strike

Result? Modem, motherboard, memory, graphics card, sound card -
every component attached directly to the motherboard was dead. w_tom can

say
all he likes about electrical theory,


I dunno why, he has a little trouble grasping basic electrical theory.

but experience has shown me that
lightning surges down the phone line blow modems up!


Yep that right and anyone else in the Comms/Data Comms industry would tell
you exactly the same thing.
two useful tips:
1) unplug the phone line from your modem/PC when not in use
2)use an external modem for preference - it is no guarantee but at least it
keeps lightning that one step further away from your PC

After my own
experience, I like to tell callers that the modem has acted as a fuse,

and
saved the rest of their P.C. - they seem to find this reassuring!


well while not strictly correct, I know what you mean.
Maybe for the sake of the pedants word it as : "your modem acted as a surge
arrestor and redirected the Lightning to the Mains earth"

Regards
Richard Freeman




  #2  
Old September 9th 03, 10:32 AM
Franc Zabkar
external usenet poster
 
Posts: n/a
Default

On Mon, 8 Sep 2003 17:28:57 +1000, "Richard Freeman"
put finger to keyboard and composed:

Damn just when I thought w_tom had grasped the concept. Once again w_tom
goes on with his fantasy that Lightning comes in via AC mains and exits via
the phone Line.


I was skeptical, too, until I saw it for myself. See this post:

http://groups.google.com/groups?selm...&output=gplain


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.
  #3  
Old September 10th 03, 02:12 AM
Richard Freeman
external usenet poster
 
Posts: n/a
Default


"Franc Zabkar" wrote in message
...
On Mon, 8 Sep 2003 17:28:57 +1000, "Richard Freeman"
put finger to keyboard and composed:

Damn just when I thought w_tom had grasped the concept. Once again w_tom
goes on with his fantasy that Lightning comes in via AC mains and exits

via
the phone Line.


I was skeptical, too, until I saw it for myself. See this post:


http://groups.google.com/groups?selm...goblue.net. a
u&output=gplain



Firstly where is this earth on the Telephone line ????? - It does not exist.
some (in Australia very few) phone lines have surge arrestors but these are
not generally implemented as they have proven to be ineffective in the case
of near/Direct strikes.

going through your list :

Firstly, my friend's neighbour lost his electrical distribution box,
so this confirms that the strike came in on the mains.


Well Maybe and I have not said it never comes in via Mains just that if it
does it is so uncommon that I have not seen it.
Reading through the list of damage however suggests that your friend
suffered a direct strike in which case :

A) all bets are off
B) a Lightning strike that has blown the ****e out of a switchboard is
barely going to flinch at blowing the ****e out of a MOV
C) Equally likely and the more probable scenario is that your friends house
was hit and the Lightning followed the path to the best Earth available -
that of the MEN Mains

Failure of PCtel DAA module (plug-in type for PCChips M585LMR
motherboard). Symptom was "NO DIALTONE". Parallel telephone was
undamaged. Both phone cables were plugged into a "protected" power
board.


Plug in module connected to the phone line - still matches the scenario that
the strike came in via Phone and exited via Mains
The parallel phone most likely rode out the strike. In fact this sounds like
a module in a PC if the strike came in via the Mains and exited via the
phone line why wasnt the PSU fried ? the more likely scenario is that the
strike came in via the phone line and headed for the chassis earth on the
PC.

(2) Portable telephone base station - shorted 15V zener diode at tip
and ring inputs.


Powered phone connected to the phone line - still matches the scenario that
the strike came in via Phone and exited via Mains

(3) Television - shorted rectifier diode, blown fuse, and failures in
the +5V regulator, remote sensor, and microcontroller.

(4) Two VCRs - CPU and power supply failures.


Nasty sounds like a direct strike which also entered via the TV aerial and
headed for the earth provided via the double insulated mains - note no phone
line involved here

(5) Audio unit - CPU failure, P/S OK.

Dont know what this was but if double insulated equipment connected to the
VCR/TV then Lightning was probably still travelling in via the TV aerial and
had not dissipated completely via the VCR or TV Again no phone line
connected here

(6) Security light - faulty power controller, light dims but won't
turn off.

Sounds like a direct strike The Light being installed outdoors probably
copped a secondary strike not the full Strike - you would have found that
one of w_toms surge busters would not have saved this anyway. Also no phone
line involved here

(7) TV - blown fuse, damage to P/S

entered via the TV aerial headed for the AC mains again no phone line
involved here

Well sounds like your Lightning still mostly obeyed the laws of Physics and
entered by unearthed / poorly earthed paths and headed straight for the best
earth available that of the AC Mains. as an addendum the mains in this
instance probably rode out the strike to a certain degree but in all the
cases a path for the lightning to have entered by other than AC mains
exsists.
Lightning aint Rocket science it obeys the laws of physics - it is just with
high energy events such as lightning different laws of physics often come in
to play.
Lightning seeks a path to the best earth it can find and note here that a
single earth stake buried in the ground is more often than not hardly the
best earth available the MEN system however used for 240/415V mains
distribution however frequently offers a superior earth for Lightning
strikes

Regards
Richard Freeman




  #4  
Old September 14th 03, 11:44 PM
Franc Zabkar
external usenet poster
 
Posts: n/a
Default

On Wed, 10 Sep 2003 11:12:46 +1000, "Richard Freeman"
put finger to keyboard and composed:


"Franc Zabkar" wrote in message
.. .
On Mon, 8 Sep 2003 17:28:57 +1000, "Richard Freeman"
put finger to keyboard and composed:

Damn just when I thought w_tom had grasped the concept. Once again w_tom
goes on with his fantasy that Lightning comes in via AC mains and exits

via
the phone Line.


I was skeptical, too, until I saw it for myself. See this post:


http://groups.google.com/groups?selm...goblue.net. a
u&output=gplain



Firstly where is this earth on the Telephone line ????? - It does not exist.


In normal circumstances the phone line ground is at the exchange.
However, in the case of a lightning strike, the nearest earth is the
ground surrounding the cable. In any case, if lightning were to hit
the ground, then why would it not dissipate itself in the general mass
of earth rather than travelling all the way into the house and onto
its local mains earth? Granted, the earth is not homogenous, so a
lower potential _could_ exist at the dwelling, but it would seem more
likely that an earth strike would not propagate too far away from the
epicentre.

some (in Australia very few) phone lines have surge arrestors but these are
not generally implemented as they have proven to be ineffective in the case
of near/Direct strikes.


going through your list :

Firstly, my friend's neighbour lost his electrical distribution box,
so this confirms that the strike came in on the mains.


Well Maybe and I have not said it never comes in via Mains just that if it
does it is so uncommon that I have not seen it.


I have seen it twice at the same dwelling, with similar results. On
the second occasion the datapump of an internal 33.6K ISA Rockwell
modem was damaged, but the only other problem with the entire PC was a
faulty IRQ3 signal on the ISA bus. That's two PCs, neither of which
sustained any damage other than a faulty modem DSP/DAA.

Reading through the list of damage however suggests that your friend
suffered a direct strike in which case :

A) all bets are off
B) a Lightning strike that has blown the ****e out of a switchboard is
barely going to flinch at blowing the ****e out of a MOV
C) Equally likely and the more probable scenario is that your friends house
was hit and the Lightning followed the path to the best Earth available -
that of the MEN Mains

Failure of PCtel DAA module (plug-in type for PCChips M585LMR
motherboard). Symptom was "NO DIALTONE". Parallel telephone was
undamaged. Both phone cables were plugged into a "protected" power
board.


Plug in module connected to the phone line - still matches the scenario that
the strike came in via Phone and exited via Mains
The parallel phone most likely rode out the strike. In fact this sounds like
a module in a PC if the strike came in via the Mains and exited via the
phone line why wasnt the PSU fried ?


Clearly the strike struck the mains at some point, so one would
intuitively expect that everything connected to the mains would have
suffered significant damage, as you say. The fact that the PSU
survived suggests that the major part of the potential difference
appeared across the DAA of the modem (???).

the more likely scenario is that the
strike came in via the phone line and headed for the chassis earth on the
PC.


So we have two strikes, one on the mains and another on the phone
line?

(2) Portable telephone base station - shorted 15V zener diode at tip
and ring inputs.


Powered phone connected to the phone line - still matches the scenario that
the strike came in via Phone and exited via Mains

(3) Television - shorted rectifier diode, blown fuse, and failures in
the +5V regulator, remote sensor, and microcontroller.

(4) Two VCRs - CPU and power supply failures.


Nasty sounds like a direct strike which also entered via the TV aerial and
headed for the earth provided via the double insulated mains - note no phone
line involved here


So now we have three strikes, one on the mains, a second on the phone
line, and a third on the aerial?

BTW, no tuners or IF stages were damaged.

(5) Audio unit - CPU failure, P/S OK.

Dont know what this was but if double insulated equipment connected to the
VCR/TV then Lightning was probably still travelling in via the TV aerial and
had not dissipated completely via the VCR or TV Again no phone line
connected here


No aerial, no phone line, just mains power.

(6) Security light - faulty power controller, light dims but won't
turn off.

Sounds like a direct strike The Light being installed outdoors probably
copped a secondary strike not the full Strike - you would have found that
one of w_toms surge busters would not have saved this anyway. Also no phone
line involved here

(7) TV - blown fuse, damage to P/S

entered via the TV aerial headed for the AC mains again no phone line
involved here


As before, no tuners or IF stages were damaged.

Well sounds like your Lightning still mostly obeyed the laws of Physics and
entered by unearthed / poorly earthed paths and headed straight for the best
earth available that of the AC Mains. as an addendum the mains in this
instance probably rode out the strike to a certain degree but in all the
cases a path for the lightning to have entered by other than AC mains
exsists.
Lightning aint Rocket science it obeys the laws of physics - it is just with
high energy events such as lightning different laws of physics often come in
to play.
Lightning seeks a path to the best earth it can find and note here that a
single earth stake buried in the ground is more often than not hardly the
best earth available the MEN system however used for 240/415V mains
distribution however frequently offers a superior earth for Lightning
strikes


I notice that the one thing that distinguishes a PC from most, if not
all the other equipment is the fact that it has an earth conductor.
What if this relatively small earth conductor allows the PC to float
to the strike potential? Wouldn't the full potential then appear
across the modem's DAA rather than the main part of the PC?

Regards
Richard Freeman


I wonder if there is some forensic or metallurgical method of
determining the direction of current flow in a lightning strike.


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.
  #5  
Old September 15th 03, 12:21 PM
Ed Medlin
external usenet poster
 
Posts: n/a
Default

It is almost impossible to try and "scientifically" pick apart how the
energy of a direct ground strike will affect any electrical component. There
is just so much energy envolved. I live in an area in the US Midwest that
gets many violent storms that contain a large amount of ground strikes. Just
about 2 weeks ago, we had a large strike that hit the access post of our
phone lines about 30yds from my home. It blew a 3ft deep hole and completely
destroyed the phone lines to ours and three other homes. In my home, it only
disabled our phone lines and did no damage there, but I have an outside
AC/Heat pump and it came in there and completely destroyed my climate
control system. No other damage in my house. All the other homes had all
their phone outlets burned to a crisp and all phones and at least the modems
for their computers were fried. When there is that much energy, wet ground
and so many ways for the energy to enter and exit there just aren't enough
constants to analize how that energy is going to dissipate itself. There is
also no foolproof method of protecting your electronics. I have used good
quality UPSs on my electronics for some 5yrs and have been lucky since then.
Before that, I used various brands of surge protectors and was constantly
having lightning damage. I guess what I am saying is that, yes, the energy
will follow the path of least resistance, but with that much energy to
dissipate, there are lots of paths it may follow.


Ed


  #6  
Old September 15th 03, 12:39 PM
Strontium
external usenet poster
 
Posts: n/a
Default

Are you related to Ed LIGHT? You, both, have a very annoying habit of not
knowing how to quote.


It's helpful, in the very least of the sense.


SHEESH


SEE QUOTE, below.

-
Ed Medlin stood up at show-n-tell, in
, and said:

It is almost impossible to try and "scientifically" pick apart
how the energy of a direct ground strike will affect any electrical
component. There is just so much energy envolved. I live in an area
in the US Midwest that gets many violent storms that contain a large
amount of ground strikes. Just about 2 weeks ago, we had a large
strike that hit the access post of our phone lines about 30yds from
my home. It blew a 3ft deep hole and completely destroyed the phone
lines to ours and three other homes. In my home, it only disabled our
phone lines and did no damage there, but I have an outside AC/Heat
pump and it came in there and completely destroyed my climate control
system. No other damage in my house. All the other homes had all
their phone outlets burned to a crisp and all phones and at least the
modems for their computers were fried. When there is that much
energy, wet ground and so many ways for the energy to enter and exit
there just aren't enough constants to analize how that energy is
going to dissipate itself. There is also no foolproof method of
protecting your electronics. I have used good quality UPSs on my
electronics for some 5yrs and have been lucky since then. Before
that, I used various brands of surge protectors and was constantly
having lightning damage. I guess what I am saying is that, yes, the
energy will follow the path of least resistance, but with that much
energy to dissipate, there are lots of paths it may follow.


Ed


--
Strontium

"It's no surprise, to me. I am my own worst enemy. `Cause every
now, and then, I kick the livin' **** `outta me." - Lit


  #7  
Old September 16th 03, 08:15 AM
Richard Freeman
external usenet poster
 
Posts: n/a
Default

--------snipped for brevity------------


Firstly where is this earth on the Telephone line ????? - It does not

exist.

In normal circumstances the phone line ground is at the exchange.
However, in the case of a lightning strike, the nearest earth is the
ground surrounding the cable. In any case, if lightning were to hit
the ground, then why would it not dissipate itself in the general mass
of earth rather than travelling all the way into the house and onto
its local mains earth? Granted, the earth is not homogenous, so a
lower potential _could_ exist at the dwelling, but it would seem more
likely that an earth strike would not propagate too far away from the
epicentre.


Firstly A single earth point is usually a relatively poor earth often
providing up to tens of Ohms Resistance to 'earth' when Lightning hits say
an earth stake that earth point typically rises to 50,000V or more above
nominal Earth as a result.
There have been many cases where a Lightning strike to the ground has blown
through the insulation of a cable and travelled through it to a better
ground however this usually also causes physical damage to the phone cable.

Secondly the Phone line is not earthed back at the exchange it is in fact
floating above ground potential - It needs to be as it is a Balanced
Circuit.

Thirdly the DC resistance alone of a phone line is fairly high typically
being in the order of a hundred or more Ohms especially when compared to the
mains.

In other words any earth on a typical Phone line is nowhere near as
effective as the earth provided by the MEN AC distribution System.


some (in Australia very few) phone lines have surge arrestors but these

are
not generally implemented as they have proven to be ineffective in the

case
of near/Direct strikes.


going through your list :

Firstly, my friend's neighbour lost his electrical distribution box,
so this confirms that the strike came in on the mains.


Well Maybe and I have not said it never comes in via Mains just that if

it
does it is so uncommon that I have not seen it.


I have seen it twice at the same dwelling, with similar results. On
the second occasion the datapump of an internal 33.6K ISA Rockwell
modem was damaged, but the only other problem with the entire PC was a
faulty IRQ3 signal on the ISA bus. That's two PCs, neither of which
sustained any damage other than a faulty modem DSP/DAA.


So the damage was to the modem both times! this was likely to have come via
AC mains because ?

Reading through the list of damage however suggests that your friend
suffered a direct strike in which case :

A) all bets are off
B) a Lightning strike that has blown the ****e out of a switchboard is
barely going to flinch at blowing the ****e out of a MOV
C) Equally likely and the more probable scenario is that your friends

house
was hit and the Lightning followed the path to the best Earth available -
that of the MEN Mains

Failure of PCtel DAA module (plug-in type for PCChips M585LMR
motherboard). Symptom was "NO DIALTONE". Parallel telephone was
undamaged. Both phone cables were plugged into a "protected" power
board.


Plug in module connected to the phone line - still matches the scenario

that
the strike came in via Phone and exited via Mains
The parallel phone most likely rode out the strike. In fact this sounds

like
a module in a PC if the strike came in via the Mains and exited via the
phone line why wasnt the PSU fried ?


Clearly the strike struck the mains at some point, so one would
intuitively expect that everything connected to the mains would have
suffered significant damage, as you say. The fact that the PSU
survived suggests that the major part of the potential difference
appeared across the DAA of the modem (???).


most likely it came in via the floating phone line and headed for the MEN
earth - it was possibley even sufficent to cause localised EPR (Earth
Potential Rise) however given the relatively low impedance House wiring
(against the Higher impedance phone line for eg ) and the relatively high
impedance path from the phone line to the Mains earth most of the voltage
for the strike would have appeared between the phone line and the mains
earth.

the more likely scenario is that the
strike came in via the phone line and headed for the chassis earth on the
PC.


So we have two strikes, one on the mains and another on the phone
line?


Nope one strike most likely direct to the house/Aerial/Phone line and a
****e load of current heading for the MEN earth inducing all sorts of
voltages in and around the house wiring.

(2) Portable telephone base station - shorted 15V zener diode at tip
and ring inputs.


Powered phone connected to the phone line - still matches the scenario

that
the strike came in via Phone and exited via Mains

(3) Television - shorted rectifier diode, blown fuse, and failures in
the +5V regulator, remote sensor, and microcontroller.

(4) Two VCRs - CPU and power supply failures.


Nasty sounds like a direct strike which also entered via the TV aerial

and
headed for the earth provided via the double insulated mains - note no

phone
line involved here


So now we have three strikes, one on the mains, a second on the phone
line, and a third on the aerial?


Nope still only one direct Strike and a bunch of induced current in various
bits of metal a single Lightning strike can and often does induce fairly
high currents/voltages through nearby wiring especially in a Direct (or even
near) Strike. One main strike though.
bear in mind that w_tom s 'whole house protection' would most likely not
have saved anything in this strike either.


BTW, no tuners or IF stages were damaged.

(5) Audio unit - CPU failure, P/S OK.

Dont know what this was but if double insulated equipment connected to

the
VCR/TV then Lightning was probably still travelling in via the TV aerial

and
had not dissipated completely via the VCR or TV Again no phone line
connected here


No aerial, no phone line, just mains power.


still have no idea what this is - speaker cables or signal cables ?


(6) Security light - faulty power controller, light dims but won't
turn off.

Sounds like a direct strike The Light being installed outdoors probably
copped a secondary strike not the full Strike - you would have found

that
one of w_toms surge busters would not have saved this anyway. Also no

phone
line involved here

(7) TV - blown fuse, damage to P/S

entered via the TV aerial headed for the AC mains again no phone line
involved here


As before, no tuners or IF stages were damaged.


Double insulated telly though most likely so that the highest impedance part
of the path to earth (and hence the higher voltage across components) would
have been through the PSU. The TV most likely even had some surge supression
for thhe Aerial which would have excacerbated this failure.


Well sounds like your Lightning still mostly obeyed the laws of Physics

and
entered by unearthed / poorly earthed paths and headed straight for the

best
earth available that of the AC Mains. as an addendum the mains in this
instance probably rode out the strike to a certain degree but in all the
cases a path for the lightning to have entered by other than AC mains
exsists.
Lightning aint Rocket science it obeys the laws of physics - it is just

with
high energy events such as lightning different laws of physics often come

in
to play.
Lightning seeks a path to the best earth it can find and note here that a
single earth stake buried in the ground is more often than not hardly the
best earth available the MEN system however used for 240/415V mains
distribution however frequently offers a superior earth for Lightning
strikes


I notice that the one thing that distinguishes a PC from most, if not
all the other equipment is the fact that it has an earth conductor.
What if this relatively small earth conductor allows the PC to float
to the strike potential? Wouldn't the full potential then appear
across the modem's DAA rather than the main part of the PC?


The earth conducter to a PC is going to still going to have a resistance of
a fraction of an ohm against over 1000's of ohms to earth via the Phone line



Regards
Richard Freeman


I wonder if there is some forensic or metallurgical method of
determining the direction of current flow in a lightning strike.


why ?
just think about it compare the two earths -

MEN AC Mains earth = fraction of an Ohm to Earth - Directly connected to
earth stakes at not one but Several Places with a minimum wire size of 2.5mm
square (O.k with typically 2 m of 1.5mm square cable for the IEC power
lead).

Phone Line = floating above Earth potential with a Maximum wire size of
0.28mm Square not connected to an earth anywhere.

Which sounds like the better earth to you ?
If you where Lightning where would you head ?
It is not rocket science it is just fairly basic electrical theory - very
simple physics. Dont be mislead by the wilfully ignorant especially those
who seem to have a vested interest in selling 'whole house protection'.

Regards
Richard Freeman



  #8  
Old September 16th 03, 03:39 PM
w_tom
external usenet poster
 
Posts: n/a
Default

First, Richard is in Australia where he has little (probably
no) experience with effective protection. For example,
telephone companies in North America install 'whole house'
protectors at each customer's premise interface with a
connection to earth. Those effective 'whole house' protectors
make a connection from each phone wire to earth ground.
Surge on a NA phone line is earthed before it can enter the
building.

Richard would not know about this because Australian telcos
typically do not provide effective surge protectors - for
free. IOW in Australia, surges incoming on phone line are
possible - just one more path that makes surge damage even
that more likely. Just another reason why Richard would
speculate that surge protection is not possible. How would he
know? He does not have any. If he has no protectors, then
how would Richard know that properly sized and earthed surge
protectors are effective?

Second, phone lines at the exchange are earthed. Earthing
(via surge protectors) is located to be distant from the
switching computer - up to 50 meters separation. That
separation between surge protector and transistor is part of
the surge protection 'system'. Every wire entering that
switching center must first have a connection to central earth
ground - either by direct connection or via surge protector.
Why does Richard also not know this? Why is he so critical
and yet does not even know basic wiring and earthing inside a
telco switching center?

Earthing is so effective that, for example, emergency
response operators don't remove headsets during
thunderstorms. No surge entering on phone lines. This is old
technology proven long before WWII. Richard is speculating
without even having learned what has been proven generations
ago - before WWII. Effective surge protection is about
earthing the surge. So effective that surge damage is
considered a human failure.

Third, if Richard knew basics of surge protection, then he
would know that DC resistance is irrelevant. Wire impedance -
not resistance - is the important number. If he knew his
'stuff', then he would identify the component that keeps an AC
mains surge from finding earth ground via a modem. It only
takes a multimeter. A direct connection exists between some
pins on modem ICs and one AC electric wire. A direct
connection that makes modem damage from AC electric possible.
So where is this 'isolator' that keeps an AC mains surge from
finding modem? Richard tells us that AC mains cannot connect
a surge through modem. Then Richard can tell us which
component isolates modem from AC mains surges?

Richard also does not know the energy content of a lightning
strike. He only speculates. Alan Taylor of the US Forestry
Service demonstrated the energy content. In more than 95% of
lightning strikes to trees, the strike left no perceptible
indication that a strike had even occurred. That's right.
Lightning strikes typically are not high energy events. Many
are such low energy events as to not even leave indication.
Lightning is a high power event; not high energy event.
Richard should enlighten us with numbers of his high energy
lightning strike. Therein lies another problem with his
speculations. He provides no numbers to go along with his no
experience.

In the meantime, even the US Army demonstrates in training
manuals what is required to earth a direct lightning strike.
They require 10 AWG (2.5 mm dia) wires to connect lightning
rod to earth. That thin wire connects the direct lightning
strike from air terminal to earth without damage - because
energy content in lightning is that small. Just more numbers.

Lightning is easily earthed without damage. The art of
surge protection is earthing - to keep the surge outside of
the building.

One path for destructive surge that is permitted inside a
building: incoming on AC electric, destructively through mode,
and outgoing to earth ground on phone line. Damage because
one incoming wire - AC electric - was not earthed (via 'whole
house' surge protector) before entering building.

Effective surge protection is about earthing every incoming
wire before it can enter the building. Once inside a
building, the surge will find numerous, destructive paths to
earth ground. Surge protectors are only as effective as their
earth ground.

Richard Freeman is invited to describe the component that
keeps an AC mains surge from finding path through modem.
Richard is invited to put up some energy numbers for a CG
lightning strike. Richard is invited to contradict US Army
Training Manual 5-690; to prove that earth direct lightning
strikes cannot be earthed using only 10 AWG (25 amp) wires.
Richard is invited to put some scientific numbers up with his
speculations. If he cannot provide the numbers, then he is
only promoting junk science reasoning.

In the meantime, a common destructive path for modems is
incoming on AC electric and outgoing to earth ground via phone
line. A path proven too often by tracing the surge and
replacing damaged components in that path. It called
experience that is in agreement with underlying theory,
research papers, and industry professionals.


Richard Freeman wrote:

--------snipped for brevity------------

Firstly where is this earth on the Telephone line ????? - It does not

exist.

In normal circumstances the phone line ground is at the exchange.
However, in the case of a lightning strike, the nearest earth is the
ground surrounding the cable. In any case, if lightning were to hit
the ground, then why would it not dissipate itself in the general mass
of earth rather than travelling all the way into the house and onto
its local mains earth? Granted, the earth is not homogenous, so a
lower potential _could_ exist at the dwelling, but it would seem more
likely that an earth strike would not propagate too far away from the
epicentre.


Firstly A single earth point is usually a relatively poor earth often
providing up to tens of Ohms Resistance to 'earth' when Lightning hits say
an earth stake that earth point typically rises to 50,000V or more above
nominal Earth as a result.
There have been many cases where a Lightning strike to the ground has blown
through the insulation of a cable and travelled through it to a better
ground however this usually also causes physical damage to the phone cable.

Secondly the Phone line is not earthed back at the exchange it is in fact
floating above ground potential - It needs to be as it is a Balanced
Circuit.

Thirdly the DC resistance alone of a phone line is fairly high typically
being in the order of a hundred or more Ohms especially when compared to the
mains.

In other words any earth on a typical Phone line is nowhere near as
effective as the earth provided by the MEN AC distribution System.

some (in Australia very few) phone lines have surge arrestors but these

are
not generally implemented as they have proven to be ineffective in the

case
of near/Direct strikes.


going through your list :

Firstly, my friend's neighbour lost his electrical distribution box,
so this confirms that the strike came in on the mains.

Well Maybe and I have not said it never comes in via Mains just that if

it
does it is so uncommon that I have not seen it.


I have seen it twice at the same dwelling, with similar results. On
the second occasion the datapump of an internal 33.6K ISA Rockwell
modem was damaged, but the only other problem with the entire PC was a
faulty IRQ3 signal on the ISA bus. That's two PCs, neither of which
sustained any damage other than a faulty modem DSP/DAA.


So the damage was to the modem both times! this was likely to have come via
AC mains because ?

Reading through the list of damage however suggests that your friend
suffered a direct strike in which case :

A) all bets are off
B) a Lightning strike that has blown the ****e out of a switchboard is
barely going to flinch at blowing the ****e out of a MOV
C) Equally likely and the more probable scenario is that your friends

house
was hit and the Lightning followed the path to the best Earth available -
that of the MEN Mains

Failure of PCtel DAA module (plug-in type for PCChips M585LMR
motherboard). Symptom was "NO DIALTONE". Parallel telephone was
undamaged. Both phone cables were plugged into a "protected" power
board.

Plug in module connected to the phone line - still matches the scenario

that
the strike came in via Phone and exited via Mains
The parallel phone most likely rode out the strike. In fact this sounds

like
a module in a PC if the strike came in via the Mains and exited via the
phone line why wasnt the PSU fried ?


Clearly the strike struck the mains at some point, so one would
intuitively expect that everything connected to the mains would have
suffered significant damage, as you say. The fact that the PSU
survived suggests that the major part of the potential difference
appeared across the DAA of the modem (???).


most likely it came in via the floating phone line and headed for the MEN
earth - it was possibley even sufficent to cause localised EPR (Earth
Potential Rise) however given the relatively low impedance House wiring
(against the Higher impedance phone line for eg ) and the relatively high
impedance path from the phone line to the Mains earth most of the voltage
for the strike would have appeared between the phone line and the mains
earth.

the more likely scenario is that the
strike came in via the phone line and headed for the chassis earth on the
PC.


So we have two strikes, one on the mains and another on the phone
line?


Nope one strike most likely direct to the house/Aerial/Phone line and a
****e load of current heading for the MEN earth inducing all sorts of
voltages in and around the house wiring.

(2) Portable telephone base station - shorted 15V zener diode at tip
and ring inputs.

Powered phone connected to the phone line - still matches the scenario

that
the strike came in via Phone and exited via Mains

(3) Television - shorted rectifier diode, blown fuse, and failures in
the +5V regulator, remote sensor, and microcontroller.

(4) Two VCRs - CPU and power supply failures.

Nasty sounds like a direct strike which also entered via the TV aerial

and
headed for the earth provided via the double insulated mains - note no

phone
line involved here


So now we have three strikes, one on the mains, a second on the phone
line, and a third on the aerial?


Nope still only one direct Strike and a bunch of induced current in various
bits of metal a single Lightning strike can and often does induce fairly
high currents/voltages through nearby wiring especially in a Direct (or even
near) Strike. One main strike though.
bear in mind that w_tom s 'whole house protection' would most likely not
have saved anything in this strike either.

BTW, no tuners or IF stages were damaged.

(5) Audio unit - CPU failure, P/S OK.

Dont know what this was but if double insulated equipment connected to

the
VCR/TV then Lightning was probably still travelling in via the TV aerial

and
had not dissipated completely via the VCR or TV Again no phone line
connected here


No aerial, no phone line, just mains power.


still have no idea what this is - speaker cables or signal cables ?

(6) Security light - faulty power controller, light dims but won't
turn off.

Sounds like a direct strike The Light being installed outdoors probably
copped a secondary strike not the full Strike - you would have found

that
one of w_toms surge busters would not have saved this anyway. Also no

phone
line involved here

(7) TV - blown fuse, damage to P/S

entered via the TV aerial headed for the AC mains again no phone line
involved here


As before, no tuners or IF stages were damaged.


Double insulated telly though most likely so that the highest impedance part
of the path to earth (and hence the higher voltage across components) would
have been through the PSU. The TV most likely even had some surge supression
for thhe Aerial which would have excacerbated this failure.

Well sounds like your Lightning still mostly obeyed the laws of Physics

and
entered by unearthed / poorly earthed paths and headed straight for the

best
earth available that of the AC Mains. as an addendum the mains in this
instance probably rode out the strike to a certain degree but in all the
cases a path for the lightning to have entered by other than AC mains
exsists.
Lightning aint Rocket science it obeys the laws of physics - it is just

with
high energy events such as lightning different laws of physics often come

in
to play.
Lightning seeks a path to the best earth it can find and note here that a
single earth stake buried in the ground is more often than not hardly the
best earth available the MEN system however used for 240/415V mains
distribution however frequently offers a superior earth for Lightning
strikes


I notice that the one thing that distinguishes a PC from most, if not
all the other equipment is the fact that it has an earth conductor.
What if this relatively small earth conductor allows the PC to float
to the strike potential? Wouldn't the full potential then appear
across the modem's DAA rather than the main part of the PC?


The earth conducter to a PC is going to still going to have a resistance of
a fraction of an ohm against over 1000's of ohms to earth via the Phone line

Regards
Richard Freeman


I wonder if there is some forensic or metallurgical method of
determining the direction of current flow in a lightning strike.


why ?
just think about it compare the two earths -

MEN AC Mains earth = fraction of an Ohm to Earth - Directly connected to
earth stakes at not one but Several Places with a minimum wire size of 2.5mm
square (O.k with typically 2 m of 1.5mm square cable for the IEC power
lead).

Phone Line = floating above Earth potential with a Maximum wire size of
0.28mm Square not connected to an earth anywhere.

Which sounds like the better earth to you ?
If you where Lightning where would you head ?
It is not rocket science it is just fairly basic electrical theory - very
simple physics. Dont be mislead by the wilfully ignorant especially those
who seem to have a vested interest in selling 'whole house protection'.

Regards
Richard Freeman

  #9  
Old September 16th 03, 05:33 PM
JAD
external usenet poster
 
Posts: n/a
Default

Those effective 'whole house' protectors
make a connection from each phone wire to earth ground.
Surge on a NA phone line is earthed before it can enter the
building.


One comment here...this also depends on the 'IN' house wiring being done correctly or is undamaged.....in older homes where the
lines have been butchered this does not hold true...
especially on the NID on the side of the house, seen them knocked off with lawnmowers etc,,....just hanging there by the wires,
ground ripped off.




"w_tom" wrote in message ...
First, Richard is in Australia where he has little (probably
no) experience with effective protection. For example,
telephone companies in North America install 'whole house'
protectors at each customer's premise interface with a
connection to earth. Those effective 'whole house' protectors
make a connection from each phone wire to earth ground.
Surge on a NA phone line is earthed before it can enter the
building.

Richard would not know about this because Australian telcos
typically do not provide effective surge protectors - for
free. IOW in Australia, surges incoming on phone line are
possible - just one more path that makes surge damage even
that more likely. Just another reason why Richard would
speculate that surge protection is not possible. How would he
know? He does not have any. If he has no protectors, then
how would Richard know that properly sized and earthed surge
protectors are effective?

Second, phone lines at the exchange are earthed. Earthing
(via surge protectors) is located to be distant from the
switching computer - up to 50 meters separation. That
separation between surge protector and transistor is part of
the surge protection 'system'. Every wire entering that
switching center must first have a connection to central earth
ground - either by direct connection or via surge protector.
Why does Richard also not know this? Why is he so critical
and yet does not even know basic wiring and earthing inside a
telco switching center?

Earthing is so effective that, for example, emergency
response operators don't remove headsets during
thunderstorms. No surge entering on phone lines. This is old
technology proven long before WWII. Richard is speculating
without even having learned what has been proven generations
ago - before WWII. Effective surge protection is about
earthing the surge. So effective that surge damage is
considered a human failure.

Third, if Richard knew basics of surge protection, then he
would know that DC resistance is irrelevant. Wire impedance -
not resistance - is the important number. If he knew his
'stuff', then he would identify the component that keeps an AC
mains surge from finding earth ground via a modem. It only
takes a multimeter. A direct connection exists between some
pins on modem ICs and one AC electric wire. A direct
connection that makes modem damage from AC electric possible.
So where is this 'isolator' that keeps an AC mains surge from
finding modem? Richard tells us that AC mains cannot connect
a surge through modem. Then Richard can tell us which
component isolates modem from AC mains surges?

Richard also does not know the energy content of a lightning
strike. He only speculates. Alan Taylor of the US Forestry
Service demonstrated the energy content. In more than 95% of
lightning strikes to trees, the strike left no perceptible
indication that a strike had even occurred. That's right.
Lightning strikes typically are not high energy events. Many
are such low energy events as to not even leave indication.
Lightning is a high power event; not high energy event.
Richard should enlighten us with numbers of his high energy
lightning strike. Therein lies another problem with his
speculations. He provides no numbers to go along with his no
experience.

In the meantime, even the US Army demonstrates in training
manuals what is required to earth a direct lightning strike.
They require 10 AWG (2.5 mm dia) wires to connect lightning
rod to earth. That thin wire connects the direct lightning
strike from air terminal to earth without damage - because
energy content in lightning is that small. Just more numbers.

Lightning is easily earthed without damage. The art of
surge protection is earthing - to keep the surge outside of
the building.

One path for destructive surge that is permitted inside a
building: incoming on AC electric, destructively through mode,
and outgoing to earth ground on phone line. Damage because
one incoming wire - AC electric - was not earthed (via 'whole
house' surge protector) before entering building.

Effective surge protection is about earthing every incoming
wire before it can enter the building. Once inside a
building, the surge will find numerous, destructive paths to
earth ground. Surge protectors are only as effective as their
earth ground.

Richard Freeman is invited to describe the component that
keeps an AC mains surge from finding path through modem.
Richard is invited to put up some energy numbers for a CG
lightning strike. Richard is invited to contradict US Army
Training Manual 5-690; to prove that earth direct lightning
strikes cannot be earthed using only 10 AWG (25 amp) wires.
Richard is invited to put some scientific numbers up with his
speculations. If he cannot provide the numbers, then he is
only promoting junk science reasoning.

In the meantime, a common destructive path for modems is
incoming on AC electric and outgoing to earth ground via phone
line. A path proven too often by tracing the surge and
replacing damaged components in that path. It called
experience that is in agreement with underlying theory,
research papers, and industry professionals.


Richard Freeman wrote:

--------snipped for brevity------------

Firstly where is this earth on the Telephone line ????? - It does not

exist.

In normal circumstances the phone line ground is at the exchange.
However, in the case of a lightning strike, the nearest earth is the
ground surrounding the cable. In any case, if lightning were to hit
the ground, then why would it not dissipate itself in the general mass
of earth rather than travelling all the way into the house and onto
its local mains earth? Granted, the earth is not homogenous, so a
lower potential _could_ exist at the dwelling, but it would seem more
likely that an earth strike would not propagate too far away from the
epicentre.


Firstly A single earth point is usually a relatively poor earth often
providing up to tens of Ohms Resistance to 'earth' when Lightning hits say
an earth stake that earth point typically rises to 50,000V or more above
nominal Earth as a result.
There have been many cases where a Lightning strike to the ground has blown
through the insulation of a cable and travelled through it to a better
ground however this usually also causes physical damage to the phone cable.

Secondly the Phone line is not earthed back at the exchange it is in fact
floating above ground potential - It needs to be as it is a Balanced
Circuit.

Thirdly the DC resistance alone of a phone line is fairly high typically
being in the order of a hundred or more Ohms especially when compared to the
mains.

In other words any earth on a typical Phone line is nowhere near as
effective as the earth provided by the MEN AC distribution System.

some (in Australia very few) phone lines have surge arrestors but these

are
not generally implemented as they have proven to be ineffective in the

case
of near/Direct strikes.

going through your list :

Firstly, my friend's neighbour lost his electrical distribution box,
so this confirms that the strike came in on the mains.

Well Maybe and I have not said it never comes in via Mains just that if

it
does it is so uncommon that I have not seen it.

I have seen it twice at the same dwelling, with similar results. On
the second occasion the datapump of an internal 33.6K ISA Rockwell
modem was damaged, but the only other problem with the entire PC was a
faulty IRQ3 signal on the ISA bus. That's two PCs, neither of which
sustained any damage other than a faulty modem DSP/DAA.


So the damage was to the modem both times! this was likely to have come via
AC mains because ?

Reading through the list of damage however suggests that your friend
suffered a direct strike in which case :

A) all bets are off
B) a Lightning strike that has blown the ****e out of a switchboard is
barely going to flinch at blowing the ****e out of a MOV
C) Equally likely and the more probable scenario is that your friends

house
was hit and the Lightning followed the path to the best Earth available -
that of the MEN Mains

Failure of PCtel DAA module (plug-in type for PCChips M585LMR
motherboard). Symptom was "NO DIALTONE". Parallel telephone was
undamaged. Both phone cables were plugged into a "protected" power
board.

Plug in module connected to the phone line - still matches the scenario

that
the strike came in via Phone and exited via Mains
The parallel phone most likely rode out the strike. In fact this sounds

like
a module in a PC if the strike came in via the Mains and exited via the
phone line why wasnt the PSU fried ?

Clearly the strike struck the mains at some point, so one would
intuitively expect that everything connected to the mains would have
suffered significant damage, as you say. The fact that the PSU
survived suggests that the major part of the potential difference
appeared across the DAA of the modem (???).


most likely it came in via the floating phone line and headed for the MEN
earth - it was possibley even sufficent to cause localised EPR (Earth
Potential Rise) however given the relatively low impedance House wiring
(against the Higher impedance phone line for eg ) and the relatively high
impedance path from the phone line to the Mains earth most of the voltage
for the strike would have appeared between the phone line and the mains
earth.

the more likely scenario is that the
strike came in via the phone line and headed for the chassis earth on the
PC.

So we have two strikes, one on the mains and another on the phone
line?


Nope one strike most likely direct to the house/Aerial/Phone line and a
****e load of current heading for the MEN earth inducing all sorts of
voltages in and around the house wiring.

(2) Portable telephone base station - shorted 15V zener diode at tip
and ring inputs.

Powered phone connected to the phone line - still matches the scenario

that
the strike came in via Phone and exited via Mains

(3) Television - shorted rectifier diode, blown fuse, and failures in
the +5V regulator, remote sensor, and microcontroller.

(4) Two VCRs - CPU and power supply failures.

Nasty sounds like a direct strike which also entered via the TV aerial

and
headed for the earth provided via the double insulated mains - note no

phone
line involved here

So now we have three strikes, one on the mains, a second on the phone
line, and a third on the aerial?


Nope still only one direct Strike and a bunch of induced current in various
bits of metal a single Lightning strike can and often does induce fairly
high currents/voltages through nearby wiring especially in a Direct (or even
near) Strike. One main strike though.
bear in mind that w_tom s 'whole house protection' would most likely not
have saved anything in this strike either.

BTW, no tuners or IF stages were damaged.

(5) Audio unit - CPU failure, P/S OK.

Dont know what this was but if double insulated equipment connected to

the
VCR/TV then Lightning was probably still travelling in via the TV aerial

and
had not dissipated completely via the VCR or TV Again no phone line
connected here

No aerial, no phone line, just mains power.


still have no idea what this is - speaker cables or signal cables ?

(6) Security light - faulty power controller, light dims but won't
turn off.

Sounds like a direct strike The Light being installed outdoors probably
copped a secondary strike not the full Strike - you would have found

that
one of w_toms surge busters would not have saved this anyway. Also no

phone
line involved here

(7) TV - blown fuse, damage to P/S

entered via the TV aerial headed for the AC mains again no phone line
involved here

As before, no tuners or IF stages were damaged.


Double insulated telly though most likely so that the highest impedance part
of the path to earth (and hence the higher voltage across components) would
have been through the PSU. The TV most likely even had some surge supression
for thhe Aerial which would have excacerbated this failure.

Well sounds like your Lightning still mostly obeyed the laws of Physics

and
entered by unearthed / poorly earthed paths and headed straight for the

best
earth available that of the AC Mains. as an addendum the mains in this
instance probably rode out the strike to a certain degree but in all the
cases a path for the lightning to have entered by other than AC mains
exsists.
Lightning aint Rocket science it obeys the laws of physics - it is just

with
high energy events such as lightning different laws of physics often come

in
to play.
Lightning seeks a path to the best earth it can find and note here that a
single earth stake buried in the ground is more often than not hardly the
best earth available the MEN system however used for 240/415V mains
distribution however frequently offers a superior earth for Lightning
strikes

I notice that the one thing that distinguishes a PC from most, if not
all the other equipment is the fact that it has an earth conductor.
What if this relatively small earth conductor allows the PC to float
to the strike potential? Wouldn't the full potential then appear
across the modem's DAA rather than the main part of the PC?


The earth conducter to a PC is going to still going to have a resistance of
a fraction of an ohm against over 1000's of ohms to earth via the Phone line

Regards
Richard Freeman

I wonder if there is some forensic or metallurgical method of
determining the direction of current flow in a lightning strike.


why ?
just think about it compare the two earths -

MEN AC Mains earth = fraction of an Ohm to Earth - Directly connected to
earth stakes at not one but Several Places with a minimum wire size of 2.5mm
square (O.k with typically 2 m of 1.5mm square cable for the IEC power
lead).

Phone Line = floating above Earth potential with a Maximum wire size of
0.28mm Square not connected to an earth anywhere.

Which sounds like the better earth to you ?
If you where Lightning where would you head ?
It is not rocket science it is just fairly basic electrical theory - very
simple physics. Dont be mislead by the wilfully ignorant especially those
who seem to have a vested interest in selling 'whole house protection'.

Regards
Richard Freeman



  #10  
Old September 17th 03, 04:11 AM
Richard Freeman
external usenet poster
 
Posts: n/a
Default

Ahhh more Ignorance from the annonymous w_tom

"w_tom" wrote in message
...
First, Richard is in Australia where he has little (probably
no) experience with effective protection.


So is Frank Zabkar or did you fail to notice ?

For example,
telephone companies in North America install 'whole house'
protectors at each customer's premise interface with a
connection to earth. Those effective 'whole house' protectors
make a connection from each phone wire to earth ground.
Surge on a NA phone line is earthed before it can enter the
building.


Provided :
A) The surge arrestor does not evaporate or burn out - whichthey will and do
in Direct/Near strikes
B) The earth consists of more than a Single Earth stake

Richard would not know about this because Australian telcos
typically do not provide effective surge protectors - for
free. IOW in Australia, surges incoming on phone line are
possible - just one more path that makes surge damage even
that more likely. Just another reason why Richard would
speculate that surge protection is not possible.


Wrong the reason I know Telco Surge protection is no defense against near or
direct strikes is that I have seen Time and Time again surge protection
literally blown off the distribution frame (where it has been installed) and
equipment on those lines dead following near or direct strikes.

How would he
know? He does not have any. If he has no protectors, then
how would Richard know that properly sized and earthed surge
protectors are effective?


how big then I have certainly seen 1 Joule MOVs destroyed - yes with short
Earth leads to the mains/Switchboard earth stake

Second, phone lines at the exchange are earthed. Earthing
(via surge protectors) is located to be distant from the
switching computer - up to 50 meters separation. That
separation between surge protector and transistor is part of
the surge protection 'system'. Every wire entering that
switching center must first have a connection to central earth
ground - either by direct connection or via surge protector.
Why does Richard also not know this? Why is he so critical
and yet does not even know basic wiring and earthing inside a
telco switching center?


Well w_tom is showing his lack of knowledge about how exchanges are
installed by feeding more erronous information

Telephone exchanges have very extensive earthing systems - this is true
All metal work in the exchange is tied to earth
Exchanges are usually fed by underground cables and enter through an earthed
metal sheath
the underground conduits near the exchange are earthed back to the exchange
earth
Exchange Buildings have extensive Lightning protection
Surge protection for individual lines is on the LI board - But this is only
effective for distant strikes however taking the other precautions ensures
that most strikes are distant - in the event of direct strikes damage can
and does still occour although this is more common on RCMs or RIMs (which do
have Surge arrestors connected directly to earth stakes ie with less than 1M
of wire) which do suffer damage during direct or near strikes which usually
also completely destroys the surge arrestors ( should really be called
diverters).

Earthing is so effective that, for example, emergency
response operators don't remove headsets during
thunderstorms. No surge entering on phone lines. This is old
technology proven long before WWII. Richard is speculating
without even having learned what has been proven generations
ago - before WWII. Effective surge protection is about
earthing the surge. So effective that surge damage is
considered a human failure.


emergency operators used to be sited in exchanges for all the reasons listed
above or in buildings in city areas where the phone lines firstly terminate
on a PABX or local switch (which is going to effectively isolate the
operator from any Lightning injury ) however nowadays emergency operators
are in call centres which are fed by Fibre optics systems which for some
very strange reason do not seem to have the problems that normal phone lines
do they are however usually connected to mains though often with no surge
protection other than what is provided by the equipment maunfacurer yet very
rarely suffer outages let alone injury I wonder why ?

Third, if Richard knew basics of surge protection, then he
would know that DC resistance is irrelevant. Wire impedance -
not resistance - is the important number.


perhaps w_tom can explain how a single strand 0.28mm square wire is going to
exhibit a lower impedance than a multi-strand 2.5mm square wire

oops it does not not under any circumstance maybe if w_tom knew basic
Electrical theory and basic Physics he would not make these sorts of errors.
I quoted DC resistance as it is readily measurable in the examples I used
the impedance will be higher I admit but the imedance of the Mains wiring is
still going to be a fraction of the impedance of the phone line.

Note here that w_tom top posts so that people cannot take the original
statement in context and therefore see how ridiculous w_toms argument is

If he knew his
'stuff', then he would identify the component that keeps an AC
mains surge from finding earth ground via a modem. It only
takes a multimeter. A direct connection exists between some
pins on modem ICs and one AC electric wire.


It does ????
Which modem IC pins would they be ???
thats funny all ( I have found 6 so far ) the modems I have here (and a
number are made in america ) are double insulated - THERE IS NO DIRECT
CONNECTION BETWEEN ANY PINS ON ANY IC IN THE MODEM AND AC MAINS !
w_tom is merely showing his ignorance again - Modems nowadays are built for
an international market and the easiest way of dealing with all the power
variations is to power the modem from a (double insulated) plugpack even
older modems which I used to Repair (that right component level repair)
which did have metal cases had no direct connection between active or
Neutral and the internal Electronics they did however have a mains earth
connected to the internal Electronics and Lightning damage was typically
between the Line interface and the Mains earth with other damage scattered
around the modem depending on how close the strike was.
Modern modems that are double insulated are effectively earthed via the
Serial cable back to the PC (every PC I have seen has an insulated case -
with the exception of Laptops) which is why damage can and often does
include damage to the DSP in the modem and sometimes the serial interface in
the PC.

A direct
connection that makes modem damage from AC electric possible.
So where is this 'isolator' that keeps an AC mains surge from
finding modem? Richard tells us that AC mains cannot connect
a surge through modem. Then Richard can tell us which
component isolates modem from AC mains surges?


It is a very simple device in use since before World War 1 called a
Transformer another very simple device which has been in use for well over
100 years is called a capacitor

Richard also does not know the energy content of a lightning
strike. He only speculates. Alan Taylor of the US Forestry
Service demonstrated the energy content. In more than 95% of
lightning strikes to trees, the strike left no perceptible
indication that a strike had even occurred. That's right.


Hmmm lets see a non conductive (wooden tree trunk does not conduct
electricity - Lightning) but the conductive water wetting the Tree trunk
does - gee what a surprise. This still does not explain the Trees that are
blown to pieces by Lightning Strikes though. Actually it does not seem to
explain the damage that this 'harmless' Lightning does do.


Lightning strikes typically are not high energy events. Many
are such low energy events as to not even leave indication.
Lightning is a high power event; not high energy event.
Richard should enlighten us with numbers of his high energy
lightning strike. Therein lies another problem with his
speculations. He provides no numbers to go along with his no
experience.


I have given the Numbers before but w_tom has ignored them as they are too
inconvenient to his arguments but once more for the dummy :
Lightning does vary in strength but is Typically between 1,000,000,000 and
10,000,000,000 Joules (thanks Professor Martin A. Uman,Professor of
Electrical and Computer Engineering at the University of Florida,
Gainsville)

In the meantime, even the US Army demonstrates in training
manuals what is required to earth a direct lightning strike.
They require 10 AWG (2.5 mm dia) wires to connect lightning
rod to earth. That thin wire connects the direct lightning
strike from air terminal to earth without damage - because
energy content in lightning is that small. Just more numbers.


oh thats funny sothe MEN earth is adequate ?


Lightning is easily earthed without damage. The art of
surge protection is earthing - to keep the surge outside of
the building.


True cant disagree here

One path for destructive surge that is permitted inside a
building: incoming on AC electric, destructively through mode,
and outgoing to earth ground on phone line. Damage because
one incoming wire - AC electric - was not earthed (via 'whole
house' surge protector) before entering building.


a fairly rare event however. The low imedance nature of the Mains
distribution System and the superior nature of the Earth provide via MEN
power distribution means that the MEN AC mains absorbs most of the few (very
few) strikes that avoid the Neutral or Earth wires in the power reticulation
System - NB Telephone distribution cables DO NOT have this Earth and hence
(even when buried underground) are far more susceptible to damage and surges
from Lightning.

Effective surge protection is about earthing every incoming
wire before it can enter the building. Once inside a
building, the surge will find numerous, destructive paths to
earth ground. Surge protectors are only as effective as their
earth ground.


True however Surge protectors are also limited by their ability to withstand
High Currents - typically in the order of 4500 Amps or more for 100uSec with
a tail averaging 500-1000A for another 0.25 Sec

Richard Freeman is invited to describe the component that
keeps an AC mains surge from finding path through modem.


wrong way around again the surge comes from the high impedance phone line
and seeks Mains (MEN) earth w_tom has still not explained in any truthful
manner how Lightning is effectively earthed on a phone line (0.28mm square
single strand copper copper wire ,No direct Earth connection etc) but not
on an MEN power distribution System which has one Wire tied directly to an
Earth stake at not one place but every Switchboard it enters (on a typical
street around near where I live the Neutral is tied to earth approximately
30Metres or so and all connected together with at least 6mm square multi
strand Copper cable.

Richard is invited to put up some energy numbers for a CG
lightning strike. Richard is invited to contradict US Army
Training Manual 5-690; to prove that earth direct lightning
strikes cannot be earthed using only 10 AWG (25 amp) wires.
Richard is invited to put some scientific numbers up with his
speculations. If he cannot provide the numbers, then he is
only promoting junk science reasoning.


Thats funny w_tom is accusing me of saying what he is claiming namely that
Lightning on a MEN mains distribution System cannot be effectively earthed
by Low impedance cabling connected to multiple earths -
I have not and have never made this claim !
what I have said is that MOVs in the event of a near or direct strike cannot
be expected to handle shunting the strike effectively to earth this has been
proved time and time and time again - not usually on AC mains where the MEN
system effectively absorbs and shunts most of the strike to earth - but on
Telephone and Data Lines where the copper is floating above Earth Potential
and is not earthed at any point (except for the ill fated 'surge
arrestors').
I have also not made the claim that in the event of a Direct strike no
damage ever occours via surges on the AC cabling - what I have said is that
Destructive Lightning surges on mains cabling is very very Rare and that the
most common pathe for Lightning damage is :
In from unearthed or poorly earthed sources such as aerials, phone lines and
Data lines and out to the MEN Mains earth
- note with single point Earthing as often erronously used for Lightning
protection any effective earthing must be tied back to the far more
effective MEN Earth as a single earth stake in the event of a Lightning
strike will exhibit an EPR (I see w_toms favourite polyphasor site refers to
it as GPR) in excess of 50,000V


In the meantime, a common destructive path for modems is
incoming on AC electric and outgoing to earth ground via phone
line. A path proven too often by tracing the surge and
replacing damaged components in that path. It called
experience that is in agreement with underlying theory,
research papers, and industry professionals.


Arse about face as would be expected from someone who has shown little grasp
of basic Physics, or Basic Electrical Theory, very little knowledge of MEN
power distribution, effective Earthing Techniques and almost no knowledge of
Telephony or Data communications.
His claims go in the face of experience that is in agreement with Electrical
Theory, Basic Physics Reasearch Papers and Industry Professionals (in the
IT&T Industry).

I shall summarise my Arguments here to keep the facts that w_tom avoids
straight :

Most Lightning damage enters via the Phone line, Aerials or other unearthed
wiring and exits to the MEN Mains earth.
Surge arrestors in the event of a near or direct strike if they are doing
their job do not usually last long enough to be effective.
Surge arrestors on AC mains do usually outlast those on phone lines mainly
because the MEN power distribution system does a pretty good job of
absorbing Lightning strikes already.

Finally :
The best and most effective way ofprotecting your Computer in the event of a
lightning strike is firstly use an external modem - this helps keep
lightning at arms length from the computer and secondly physically
disconnect the modem from the phone when not in use especially if there is
any chance of a Thunderstorm (powering it off is not enough).

As a final note the name I sign with is my real name as I know that
everything I say is accurate however w_tom chooses to remain anonymous (I
wonder why is he scared of being sued by those who took his advice and still
suffered Lightning damage ?)

Regards
Richard Freeman


 




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