UPS with earth leakage device.
no.to...@gmail.com
night. A consultant said that it's caused by UPS/s.
But I can't understand since the UPS is designed to switch on AFTER
the mains failure. So how can it cause the mains failure.
== TIA.
ArameFarpado
> But I can't understand since the UPS is designed to switch on AFTER
> the mains failure.
wrong.
philo
Without checking it the consultant could not have had a clue...
but sure a UPS can fail just like any other device
but if the problem was traced to the UPS
chances are it was simply not grounded properly
better get someone who knows what they are doing
to check the wiring etc
no.to...@gmail.com
OK, I don't want to influence original contributions, by giving my
full present analysis. But the failure process takes a finite time.
And I insist that the UPS can only acts AFTER the beginning of the
mains 'failure process'.
Can you contribute more than "wrong" ?
---
philo wrote:
> but if the problem was traced to the UPS
>
> chances are it was simply not grounded properly
>
> better get someone who knows what they are doing
> to check the wiring etc
No, AFAIK the earth-leakage -detector works by measuring
the unbalance between the line and neutral current flow.
Since the unbalance must be returning via the earth.
So REMOVING THE EARTH to the UPS & computer circuit
'eliminates the problem'. But that's a bodge.
One needs to fully understand the problem cause
sequence.
.
== TIA.
ArameFarpado
> In article <4b44e3c5$0$275$1472...@news.sunsite.dk>, ArameFarpado
> <a-farpa...@netcabo.pt> wrote:
>
>> Em Quarta 06 Janeiro 2010 17:23, no.to...@gmail.com escreveu:
>> > But I can't understand since the UPS is designed to switch on AFTER
>> > the mains failure.
>>
>> wrong.
>
> OK, I don't want to influence original contributions, by giving my
> full present analysis. But the failure process takes a finite time.
> And I insist that the UPS can only acts AFTER the beginning of the
> mains 'failure process'.
>
> Can you contribute more than "wrong" ?
You are confusing a UPS with a emergency electric generator; those are the
ones that start working after the power goes off.
A UPS needs to keep the power up without letting it go down even for a split
second.
The only switch a ups does when the power goes off is that it stops charging
the batteries. The output of a UPS is allways given by the same circuits
regardless if the power is on or off
with power on:
main power -> AC-DC converter -> DC-AC converter -> output
-> charge batteries.
with power off:
batteries -> DC-AC converter -> output
this is the only way that an ups can keep the output on without any breaks.
so resuming: if the ups's output is given the wrong voltage, frequency,
sinosoidal wave, etc... you have two choices:
1- repair the ups
2- replace the ups.
regards
philo
> philo wrote:
>
>> but if the problem was traced to the UPS
>>
>> chances are it was simply not grounded properly
>>
>> better get someone who knows what they are doing
>> to check the wiring etc
> No, AFAIK the earth-leakage -detector works by measuring
> the unbalance between the line and neutral current flow.
> Since the unbalance must be returning via the earth.
> So REMOVING THE EARTH to the UPS & computer circuit
> 'eliminates the problem'. But that's a bodge.
> One needs to fully understand the problem cause
> sequence.
> .
> == TIA.
>
>
OK figured it out
A ground fault occurs when the "hot" lead of the mains shorts to the
case of the equipment.
So if there was a power failure there would be no "mains" lead to short
to the cabinet...
So the conclusion is reversed from what has happened
It was a ground fault which *caused* the power interruption.
The UPS simply was on because the "mains" breaker had tripped
ArameFarpado
> No, AFAIK the earth-leakage -detector works by measuring
> the unbalance between the line and neutral current flow.
> Since the unbalance must be returning via the earth.
> So REMOVING THE EARTH to the UPS & computer circuit
> 'eliminates the problem'. But that's a bodge.
> One needs to fully understand the problem cause
> sequence.
> .
> == TIA.
if you have electrical questions, it's better to put them in
sci.electronics.basics
i can tell you that if you desconnect the earth, ther will be no more a
neutral in the output, you will have two live lines with a voltage between
them, and that could cause other issues.
Joe Pfeiffer
You can tell us anything you want, but if you tell us that you're
wrong. Standard single-phase AC works with a hot line and a neutral
line; neutral and ground are at the same potential. There should not be
any current flowing through ground.
See http://en.wikipedia.org/wiki/Ground_and_neutral
--
As we enjoy great advantages from the inventions of others, we should
be glad of an opportunity to serve others by any invention of ours;
and this we should do freely and generously. (Benjamin Franklin)
david
to say:
This is only true with a double-conversion type UPS, which most cheap PC-
type UPS's are not. Most cheap UPSs have a transfer switch in them, so
the power is actually interrupted for a few milliseconds when the mains
fail.
ArameFarpado
> ArameFarpado <a-farpa...@netcabo.pt> writes:
>
>> Em Quinta 07 Janeiro 2010 08:27, no.to...@gmail.com escreveu:
>>
>>> No, AFAIK the earth-leakage -detector works by measuring
>>> the unbalance between the line and neutral current flow.
>>> Since the unbalance must be returning via the earth.
>>> So REMOVING THE EARTH to the UPS & computer circuit
>>> 'eliminates the problem'. But that's a bodge.
>>> One needs to fully understand the problem cause
>>> sequence.
>>> .
>>> == TIA.
>>
>> if you have electrical questions, it's better to put them in
>> sci.electronics.basics
>>
>>
>> i can tell you that if you desconnect the earth, ther will be no more a
>> neutral in the output, you will have two live lines with a voltage
>> between them, and that could cause other issues.
>
> You can tell us anything you want, but if you tell us that you're
> wrong. Standard single-phase AC works with a hot line and a neutral
> line; neutral and ground are at the same potential. There should not be
> any current flowing through ground.
do you know how a neutral is created?
just answer this
a simple transformer from 230v to 110v, the primary receives a live and a
neutral, where is the neutral in the secundary side?
>
> See http://en.wikipedia.org/wiki/Ground_and_neutral
i don't have to see anything, you have, and stop reading that fake
encyclopedia
david
to say:
> Em Sexta 08 Janeiro 2010 01:40, Joe Pfeiffer escreveu:
I certainly would not want you to wire my house. Google--> "separately
derived source".
Joe Pfeiffer
> Em Sexta 08 Janeiro 2010 01:40, Joe Pfeiffer escreveu:
>
>> ArameFarpado <a-farpa...@netcabo.pt> writes:
>>
>>> Em Quinta 07 Janeiro 2010 08:27, no.to...@gmail.com escreveu:
>>>
>>>> No, AFAIK the earth-leakage -detector works by measuring
>>>> the unbalance between the line and neutral current flow.
>>>> Since the unbalance must be returning via the earth.
>>>> So REMOVING THE EARTH to the UPS & computer circuit
>>>> 'eliminates the problem'. But that's a bodge.
>>>> One needs to fully understand the problem cause
>>>> sequence.
>>>> .
>>>> == TIA.
>>>
>>> if you have electrical questions, it's better to put them in
>>> sci.electronics.basics
>>>
>>>
>>> i can tell you that if you desconnect the earth, ther will be no more a
>>> neutral in the output, you will have two live lines with a voltage
>>> between them, and that could cause other issues.
>>
>> You can tell us anything you want, but if you tell us that you're
>> wrong. Standard single-phase AC works with a hot line and a neutral
>> line; neutral and ground are at the same potential. There should not be
>> any current flowing through ground.
>
> do you know how a neutral is created?
The most relevant part of the answer is probably that it's bonded to
ground at the service panel.
> just answer this
>
> a simple transformer from 230v to 110v, the primary receives a live and a
> neutral, where is the neutral in the secundary side?
And the relevance of this to mains wiring is...
>>
>> See http://en.wikipedia.org/wiki/Ground_and_neutral
> i don't have to see anything, you have, and stop reading that fake
> encyclopedia
The fake encyclopedia bases its answer on the National Electrical Code.
Show me a source you regard as more authoritative that disagrees.
ArameFarpado
correct, it's connected to earth but not by the same connection you have in
you house...
every house has its own earth connection, the neutral is created by a earth
connection in the last transformer of the company that distributes the
energy. this is why the neutral may or may not have the same electrical
potential as the house's earth. the same way two houses's earth wiring may
not have the same potential.
anothter question if you don't mind:
a lightning bolt falls in the ground at 6 meters from you and a cow, you
suffer nothing while the cow gets electricuted and dies... why?
>
>> just answer this
>>
>> a simple transformer from 230v to 110v, the primary receives a live and a
>> neutral, where is the neutral in the secundary side?
>
> And the relevance of this to mains wiring is...
the output of a ups is not connected to the mains wiring.
if the op desconnect the earth wire, he will loose the neutral on the
output, if this ups is feeding several machines that could be a problem
>
>>>
>>> See http://en.wikipedia.org/wiki/Ground_and_neutral
>> i don't have to see anything, you have, and stop reading that fake
>> encyclopedia
>
> The fake encyclopedia bases its answer on the National Electrical Code.
not really, i myself wrote part of a article in wikipedia...
anyone qcan wrote articles in there.
> Show me a source you regard as more authoritative that disagrees.
learn electricity...
Joe
Actually, it is.
>
> every house has its own earth connection, the neutral is created by a earth
> connection in the last transformer of the company that distributes the
> energy. this is why the neutral may or may not have the same electrical
> potential as the house's earth. the same way two houses's earth wiring may
> not have the same potential.
They do. Reason? Standard home wiring these days includes tying
neutral to ground. At any outlet in your house, if properly wired,
neutral and ground are the same.
--
Joe - Linux User #449481/Ubuntu User #19733
joe at hits - buffalo dot com
"Hate is baggage, life is too short to go around pissed off all the
time..." - Danny, American History X
Joe Pfeiffer
I guess I wasn't explicit enough: it's bonded to ground at *your*
*house's* service panel -- i.e. the "breaker box". The whole point is
to avoid having neutral at a different potential than ground.
> anothter question if you don't mind:
> a lightning bolt falls in the ground at 6 meters from you and a cow, you
> suffer nothing while the cow gets electricuted and dies... why?
>
>
>>
>>> just answer this
>>>
>>> a simple transformer from 230v to 110v, the primary receives a live and a
>>> neutral, where is the neutral in the secundary side?
>>
>> And the relevance of this to mains wiring is...
> the output of a ups is not connected to the mains wiring.
> if the op desconnect the earth wire, he will loose the neutral on the
> output, if this ups is feeding several machines that could be a problem
Ah, OK -- not necessarily. Depends on the UPS configuration. Either
the neutral is passed through (if it doesn't meet the NEC requirements
for a "separably derived source"), or it is grounded within the UPS (if
it does). I'm not familiar with the internal details of typical home PC
UPSs, and familiar enough with the relevant parts of the code but I'd be
pretty surprised if a plug-in UPS were permitted to be a separably
derived source.
>>
>>>>
>>>> See http://en.wikipedia.org/wiki/Ground_and_neutral
>>> i don't have to see anything, you have, and stop reading that fake
>>> encyclopedia
>>
>> The fake encyclopedia bases its answer on the National Electrical Code.
> not really, i myself wrote part of a article in wikipedia...
> anyone qcan wrote articles in there.
>
>> Show me a source you regard as more authoritative that disagrees.
> learn electricity...
That's not a cite I'll recognize, sorry.
jellybean stonerfish
> anothter question if you don't mind:
> a lightning bolt falls in the ground at 6 meters from you and a cow, you
> suffer nothing while the cow gets electricuted and dies... why?
Tennis shoes?
Moe Trin
<4b46e73e$0$280$1472...@news.sunsite.dk>, ArameFarpado wrote:
>Joe Pfeiffer escreveu:
>> ArameFarpado <a-farpa...@netcabo.pt> writes:
>>> i can tell you that if you desconnect the earth, ther will be no
>>> more a neutral in the output, you will have two live lines with a
>>> voltage between them, and that could cause other issues.
So by your definition, there can not be a "neutral" in a car or
airplane. And by the way, have you ever heard of an isolation
transformer? Any idea _why_ they exist?
>> Standard single-phase AC works with a hot line and a neutral line;
>> neutral and ground are at the same potential. There should not be
>> any current flowing through ground.
As there is no current flowing in the ground wire, the voltage drop
will be exactly the same at both ends of a ground wire. There is
current flowing in the neutral (or 'return' lead, so the voltage
will differ. Think about the consequences of that statement.
>do you know how a neutral is created?
It is a word - it means a common reference point. It's where you
should place the black lead of your volt meter.
>just answer this
>
>a simple transformer from 230v to 110v, the primary receives a live and
>a neutral, where is the neutral in the secundary side?
Where was it defined. If all you have is two wires coming out of the
transformer, you can if you desire define _EITHER_ OR _NONE_ as the
reference point. That the two wires are now at some unknown potential
with respect to earth only means the insulation is imperfect and there
is some leakage. This is certainly a safety issue, but it doesn't
prevent a motor, light, or computer attached to the secondary from
working. If you do connect one of those leads to ground, you will
reduce the risk to a person touching _that_ lead while grounded, and
increase the risk if the person touches the _other_ lead.
>i don't have to see anything, you have, and stop reading that fake
>encyclopedia
You know you're right, and don't want facts to get in the way of that
belief. Free clue - look at the _references_ that the ``fake''
encyclopedia cites.
Old guy
Moe Trin
<slrnhkedi...@barada.griffincs.local>, Joe wrote:
>ArameFarpado <a-farpa...@netcabo.pt> wrote:
>> every house has its own earth connection, the neutral is created
>> by a earth connection in the last transformer of the company that
>> distributes the energy.
This statement is false. The "neutral" is created by people following
a standard and DEFINING "this" wire with respect of one or more "hot"
leads.
>> this is why the neutral may or may not have the same electrical
>> potential as the house's earth. the same way two houses's earth
>> wiring may not have the same potential.
>They do. Reason? Standard home wiring these days includes tying
>neutral to ground.
Within the distribution panel, the neutral and ground will be at
the same relative potential. If you compare the voltage between
that point in one house with the same point in another house, there
will be a difference - very small, but it will exist and be
measurable. The reason: wires and ground have finite resistance,
and any current flowing through those wires creates a voltage
difference according to Ohms Law.
Go out and buy two or three eight foot (2.44 meter) long copper-clad
ground rods and take them into the yard of your house (or a nearby
park - I don't care). Drive each ground rod vertically into the
ground such that the top of the rod is flush with the surface and at
least ten feet (3.05 meter) away from each other. Now take an Ohm
meter and measure the resistance between each rod. It won't be zero.
So, which one of the ground rods is at the true ground?
>At any outlet in your house, if properly wired, neutral and ground
>are the same.
WRONG! What is the resistance of #14 AWG hard drawn copper wire?
#10AWG? What is the relationship between voltage, current and
resistance? As there is no current flowing in the ground wire, what
is the voltage drop across fifty feet of #14? What's the voltage
drop with twelve amperes? I don't think it's zero, and before you
whine that the results are so low that they wouldn't hurt anyone
(about 1.57 volts), try operating an audio or video system with that
much difference in neutral voltage between components like a receiver
and recording device.
Old guy
Joe Pfeiffer
> On Fri, 08 Jan 2010, in the Usenet newsgroup comp.os.linux.hardware, in article
> <4b46e73e$0$280$1472...@news.sunsite.dk>, ArameFarpado wrote:
>
>>Joe Pfeiffer escreveu:
>
>>> ArameFarpado <a-farpa...@netcabo.pt> writes:
>
>>>> i can tell you that if you desconnect the earth, ther will be no
>>>> more a neutral in the output, you will have two live lines with a
>>>> voltage between them, and that could cause other issues.
>
> So by your definition, there can not be a "neutral" in a car or
> airplane. And by the way, have you ever heard of an isolation
> transformer? Any idea _why_ they exist?
>
>>> Standard single-phase AC works with a hot line and a neutral line;
>>> neutral and ground are at the same potential. There should not be
>>> any current flowing through ground.
>
> As there is no current flowing in the ground wire, the voltage drop
> will be exactly the same at both ends of a ground wire. There is
> current flowing in the neutral (or 'return' lead, so the voltage
> will differ. Think about the consequences of that statement.
Differ, yes. If the neutral wire is properly sized, it will not differ
significantly.
ArameFarpado
No it isn't, not in europe anyway...
neutral comes from the outside allready a neutral, it's discharge is done
right in the secundary side of the transformer that feeds the bilding or
block of bildings. and that is done with several copper rods sticked in the
ground
then every bilding has it's own copper rod, and it's earth does not connect
with neutral... it's commom to have about 2volts between earth and neutral
over here.
>
>> anothter question if you don't mind:
>> a lightning bolt falls in the ground at 6 meters from you and a cow, you
>> suffer nothing while the cow gets electricuted and dies... why?
you don't know why?
>>
>>
>>>
>>>> just answer this
>>>>
>>>> a simple transformer from 230v to 110v, the primary receives a live and
>>>> a neutral, where is the neutral in the secundary side?
>>>
>>> And the relevance of this to mains wiring is...
>> the output of a ups is not connected to the mains wiring.
>> if the op desconnect the earth wire, he will loose the neutral on the
>> output, if this ups is feeding several machines that could be a problem
>
> Ah, OK -- not necessarily. Depends on the UPS configuration. Either
> the neutral is passed through (if it doesn't meet the NEC requirements
> for a "separably derived source"), or it is grounded within the UPS (if
> it does).
neutral can't pass trought, an ups is not a light switch
> I'm not familiar with the internal details of typical home PC
> UPSs, and familiar enough with the relevant parts of the code but I'd be
> pretty surprised if a plug-in UPS were permitted to be a separably
> derived source.
well, i've been talking about real ups... the ones that stay hidden and feed
a hole network of computers, i have one in the company i work that feeds
about 400 pc's, including monitors, printers and so on...
that thing is about 2 meters tall, 1 meter sideways, and we have to replace
it's batteries every 3 years.
most home ups aren't really ups at all, some of them can't even feed the pc
after the main power is gone, they are isolation transformers.
ArameFarpado
bare feet just like the cow
ArameFarpado
not in europe
>>
>> every house has its own earth connection, the neutral is created by a
>> earth connection in the last transformer of the company that distributes
>> the energy. this is why the neutral may or may not have the same
>> electrical potential as the house's earth. the same way two houses's
>> earth wiring may not have the same potential.
>
> They do. Reason?
you stick 2 copper rods in the ground separated by 50 meters and you can
have potential between them
diferent bildings don't share earth connections, that could be dangerous.
> Standard home wiring these days includes tying
> neutral to ground.
not in europe
> At any outlet in your house, if properly wired,
> neutral and ground are the same.
no
ArameFarpado
> On 08 Jan 2010, in the Usenet newsgroup comp.os.linux.hardware, in article
> <slrnhkedi...@barada.griffincs.local>, Joe wrote:
>
>>ArameFarpado <a-farpa...@netcabo.pt> wrote:
>
>>> every house has its own earth connection, the neutral is created
>>> by a earth connection in the last transformer of the company that
>>> distributes the energy.
>
> This statement is false. The "neutral" is created by people following
> a standard and DEFINING "this" wire with respect of one or more "hot"
> leads.
???
>
> Go out and buy two or three eight foot (2.44 meter) long copper-clad
> ground rods and take them into the yard of your house (or a nearby
> park - I don't care). Drive each ground rod vertically into the
> ground such that the top of the rod is flush with the surface and at
> least ten feet (3.05 meter) away from each other. Now take an Ohm
> meter and measure the resistance between each rod. It won't be zero.
> So, which one of the ground rods is at the true ground?
each one of them is a true ground related to the place they wore stick
you people got to understand one thing:
talking about the planet's ground it isn't all at the same electrical
potential in every place. electricity is a part of nature, it's everyware
and it is in a constant movement, diferent places can be at diferent
electrical potentials.
in teory; you can get electricuted by standing with your feet on the ground
an touch a earth wire whose rod is placed at 10Km from you.
ArameFarpado
> On Fri, 08 Jan 2010, in the Usenet newsgroup comp.os.linux.hardware, in
> article <4b46e73e$0$280$1472...@news.sunsite.dk>, ArameFarpado wrote:
>
>>Joe Pfeiffer escreveu:
>
>>> ArameFarpado <a-farpa...@netcabo.pt> writes:
>
>>>> i can tell you that if you desconnect the earth, ther will be no
>>>> more a neutral in the output, you will have two live lines with a
>>>> voltage between them, and that could cause other issues.
>
> So by your definition, there can not be a "neutral" in a car or
> airplane.
no neutral, cars and planes have a body and one if it's poles is connected
to the body, usualy the negative pole.
planes have a kind of stick that touches he ground (and some cars also) to
put the body at the same potential as the ground they are standing;
planes must have this or people could get electricuted by touching the plane
body after a landing... some people more sensitive to estatic also place
this sticks in there cars so they don't get shocked when they touch them or
when the put the feet on the ground getting out of the car.
> And by the way, have you ever heard of an isolation
> transformer?
sure
> Any idea _why_ they exist?
sure, it ain't got nothing to do with it is been discussed here.
>>> Standard single-phase AC works with a hot line and a neutral line;
>>> neutral and ground are at the same potential. There should not be
>>> any current flowing through ground.
>
> As there is no current flowing in the ground wire, the voltage drop
> will be exactly the same at both ends of a ground wire. There is
> current flowing in the neutral (or 'return' lead, so the voltage
> will differ. Think about the consequences of that statement.
>
>>do you know how a neutral is created?
>
> It is a word - it means a common reference point. It's where you
> should place the black lead of your volt meter.
i didn't ask what it is or what it represents...
how do you create one?
>
>>just answer this
>>
>>a simple transformer from 230v to 110v, the primary receives a live and
>>a neutral, where is the neutral in the secundary side?
>
> Where was it defined.
there won't be one
> If all you have is two wires coming out of the
> transformer, you can if you desire define _EITHER_ OR _NONE_ as the
> reference point.
my point is, none of them will be a neutral
> That the two wires are now at some unknown potential
> with respect to earth only means the insulation is imperfect and there
> is some leakage. This is certainly a safety issue,
it is
> but it doesn't
> prevent a motor, light, or computer attached to the secondary from
> working.
electronic sensible devices can be damage
GangGreene
Guys/Gals Please
One question....
How many wires from an electical substation to the trasformer on the pole?
Answer One.
There is no neutral.
The power is returned through the earth, through a ground system.
jellybean stonerfish
2 legs??
On the side, just to keep this post entertaining...
Q: Why did the cow say "Mooooove" ?
jellybean stonerfish
What power grid are you on?
ArameFarpado
3 life phases, each AC with it's sinosoidal wave lagged 120º to the others.
every time 2 phases are positive there is one negative and vice-versa.
no need for neutral here.
>
> Answer One.
>
> There is no neutral.
> The power is returned through the earth, through a ground system.
no. the electric circuit is closed between those 3 phases
there is a triphasic wave form here
http://www.animations.physics.unsw.edu.au/jw/images/power_files/3phase.gif
notice when 2 phases are positive there 1 negative and so on.
there is allways tension between them.
http://www.windstuffnow.com/main/3_phase_basics.htm
ArameFarpado
> On Sat, 09 Jan 2010 00:05:57 +0000, ArameFarpado wrote:
>
>> Em Sexta 08 Janeiro 2010 18:28, jellybean stonerfish escreveu:
>>
>>> On Fri, 08 Jan 2010 13:17:38 +0000, ArameFarpado wrote:
>>>
>>>> anothter question if you don't mind:
>>>> a lightning bolt falls in the ground at 6 meters from you and a cow,
>>>> you suffer nothing while the cow gets electricuted and dies... why?
>>>
>>> Tennis shoes?
>>
>> bare feet just like the cow
>
> 2 legs??
the man has 2 legs and they are standing more or less at the same point, the
cow has 2 legs about 1 meter apart from the other 2... ring any bells?
>
> On the side, just to keep this post entertaining...
>
> Q: Why did the cow say "Mooooove" ?
don't know, no cow ever spoke to me... :)
Henrik Carlqvist
> Em Sï¿œbado 09 Janeiro 2010 05:28, jellybean stonerfish escreveu:
>> On Sat, 09 Jan 2010 00:05:57 +0000, ArameFarpado wrote:
>>> Em Sexta 08 Janeiro 2010 18:28, jellybean stonerfish escreveu:
>>>> On Fri, 08 Jan 2010 13:17:38 +0000, ArameFarpado wrote:
>>>>> anothter question if you don't mind:
>>>>> a lightning bolt falls in the ground at 6 meters from you and a cow,
>>>>> you suffer nothing while the cow gets electricuted and dies... why?
>>>> Tennis shoes?
>>> bare feet just like the cow
>>
>> 2 legs??
> the man has 2 legs and they are standing more or less at the same point, the
> cow has 2 legs about 1 meter apart from the other 2... ring any bells?
<OT>
If both the cow and the man were standing on their legs instead of lying
flat on the ground or even better in some pit below the ground surface the
lightning would not hit 6 meters from them. Instead the lightning would
hit the highest point connected to the ground which would probably be the
mans head. So my guess is that the cow has the best chance of surviving
after all.
</OT>
regards Henrik
--
The address in the header is only to prevent spam. My real address is:
hc3(at)poolhem.se Examples of addresses which go to spammers:
root@localhost postmaster@localhost
ArameFarpado
> ArameFarpado <a-farpa...@netcabo.pt> wrote:
>
>> Em Sábado 09 Janeiro 2010 05:28, jellybean stonerfish escreveu:
>
>>> On Sat, 09 Jan 2010 00:05:57 +0000, ArameFarpado wrote:
>
>>>> Em Sexta 08 Janeiro 2010 18:28, jellybean stonerfish escreveu:
>
>>>>> On Fri, 08 Jan 2010 13:17:38 +0000, ArameFarpado wrote:
>>>>>> anothter question if you don't mind:
>>>>>> a lightning bolt falls in the ground at 6 meters from you and a cow,
>>>>>> you suffer nothing while the cow gets electricuted and dies... why?
>
>>>>> Tennis shoes?
>
>>>> bare feet just like the cow
>>>
>>> 2 legs??
>> the man has 2 legs and they are standing more or less at the same point,
>> the cow has 2 legs about 1 meter apart from the other 2... ring any
>> bells?
>
> <OT>
>
> If both the cow and the man were standing on their legs instead of lying
> flat on the ground or even better in some pit below the ground surface the
> lightning would not hit 6 meters from them. Instead the lightning would
> hit the highest point connected to the ground which would probably be the
> mans head. So my guess is that the cow has the best chance of surviving
> after all.
>
> </OT>
>
> regards Henrik
you are driving away from the problem:
the bolt didn't hit the human or the cow, it hit the ground or a tree at 6
meters from them, the man only gets scared while the cow dies
electricuted... why?
this is all related to the fact the earth's electrical potential is not the
same in every place.
GangGreene
Don't know
GangGreene
It depends upon the reference point.
GangGreene
[putolin]
>>
>> Guys/Gals Please
>>
>> One question....
>>
>> How many wires from an electical substation to the trasformer on the
>> pole?
>
> 3 life phases, each AC with it's sinosoidal wave lagged 120º to the
> others. every time 2 phases are positive there is one negative and
> vice-versa.
>
> no need for neutral here.
>
>>
>> Answer One.
>>
>> There is no neutral.
>> The power is returned through the earth, through a ground system.
> no. the electric circuit is closed between those 3 phases
>
> there is a triphasic wave form here
> http://www.animations.physics.unsw.edu.au/jw/images/power_files/3phase.gif
>
> notice when 2 phases are positive there 1 negative and so on.
> there is allways tension between them.
>
> http://www.windstuffnow.com/main/3_phase_basics.htm
You are mixed up. I am talking residential power distribution you are
talking appliance distribution.
Notice only one leg of the 3 phase is coming down from the overhead 3 phase
lines over head to the xmfr on the pole.
If it was as you believe then two legs of the 3 phase would be in use. It's
not.
So tell me why is one leg used on the xfmr and one bare copper line going
from the xfmr down the pole to a ground rod beside the power pole for then?
Also when talking polyphase power distribution why then is a grounded
conductor used/required on the service entrance drop from the pole to the
residence?
If it worked as you say it would only require two conductors to be brought
to the residence.
http://science.howstuffworks.com/power.html
jellybean stonerfish
> Em Sábado 09 Janeiro 2010 05:28, jellybean stonerfish escreveu:
>> 2 legs??
> the man has 2 legs and they are standing more or less at the same point,
> the cow has 2 legs about 1 meter apart from the other 2... ring any
> bells?
>
OK, I understand your hypothetical.
>
>> On the side, just to keep this post entertaining...
>>
>> Q: Why did the cow say "Mooooove" ?
> don't know, no cow ever spoke to me... :)
A: Because she didn't have a horn.
ArameFarpado
> ArameFarpado wrote:
>
> [putolin]
>
>>>
>>> Guys/Gals Please
>>>
>>> One question....
>>>
>>> How many wires from an electical substation to the trasformer on the
>>> pole?
>>
>> 3 life phases, each AC with it's sinosoidal wave lagged 120º to the
>> others. every time 2 phases are positive there is one negative and
>> vice-versa.
>>
>> no need for neutral here.
>>
>>>
>>> Answer One.
>>>
>>> There is no neutral.
>>> The power is returned through the earth, through a ground system.
>> no. the electric circuit is closed between those 3 phases
>>
>> there is a triphasic wave form here
>>
http://www.animations.physics.unsw.edu.au/jw/images/power_files/3phase.gif
>>
>> notice when 2 phases are positive there 1 negative and so on.
>> there is allways tension between them.
>>
>> http://www.windstuffnow.com/main/3_phase_basics.htm
>
> You are mixed up.
oh really
> I am talking residential power distribution you are
> talking appliance distribution.
quoting you:
>>> How many wires from an electical substation to the trasformer on the
>>> pole?
substation to transformer is residential distribution? since when?
> Notice only one leg of the 3 phase is coming down from the overhead 3
> phase lines over head to the xmfr on the pole.
what poles are you talking about? high tension or low tension?
> If it was as you believe then two legs of the 3 phase would be in use.
> It's not.
what poles are you talking about... ?
http://images02.olx.com.br/ui/2/52/03/34504903_2.jpg
these ones?
> So tell me why is one leg used on the xfmr and one bare copper line going
> from the xfmr down the pole to a ground rod beside the power pole for
> then?
aren't you imagining things?
> Also when talking polyphase power distribution why then is a grounded
> conductor used/required on the service entrance drop from the pole to the
> residence?
tri-phasic residential distribution is done with 4 wires: 3 phases and 1
neutral, the neutral is necessary for monophasic devices.
in europe we have 400volts between phases and 230volts between any phase and
neutral, if you have 400volts light bolbs then you can connect them between
2 phases, but all monophasic devices are 230volts over here, so the
distribution company must provide the neutral along with the phases.
it is also common to see 3 phases and a neutral entering a bilding only for
monophasic service, that's about balance the phases: 1 phase feeds 1/3 of
the apartments, the 2nd fase the other 1/3 and the 3rd phase feeds the last
1/3 of the apartments.
the electrical company don't provide the earth wire, every bilding has it's
own and it is not requered for things to work, it's only a safety protection
that you should connect to the body of any metallic electric device.
notice that the neutral isn't just a ground connection; it is a central
point of the secundary of a triphasic transformer whose coils are connected
in "star" mode
like this
http://www.cefetsp.br/edu/jaan/mestrado/Image63.gif
A,B and C are the phases, and N will be the neutral, it is not represented
but the N line to became a real neutral needs to be grounded also.
>
> If it worked as you say it would only require two conductors to be brought
> to the residence.
>
> http://science.howstuffworks.com/power.html
>
>
http://www.howstuffworks.com/framed.htm?parent=power.htm&url=http://www.epanorama.net/documents/groundloop/mains_connectors.html
here you go, your link has a squematic showind the star center connected to
the groung but still moving on to it's destiny as a neutral wire.
Moe Trin
<4b47c84e$0$272$1472...@news.sunsite.dk>, ArameFarpado wrote:
>Joe Pfeiffer escreveu:
>> I guess I wasn't explicit enough: it's bonded to ground at *your*
>> *house's* service panel -- i.e. the "breaker box". The whole point
>> is to avoid having neutral at a different potential than ground.
>No it isn't, not in europe anyway...
That's another point - the _world_ doesn't follow European standards
any more than North American, Chinese, Brazilian or Algerian standards.
>neutral comes from the outside allready a neutral, it's discharge is
>done right in the secundary side of the transformer that feeds the
>bilding or block of bildings. and that is done with several copper
>rods sticked in the ground
"discharge" of what? Neutral is only relevant when there are more
than one phase - another word used is "common".
>then every bilding has it's own copper rod, and it's earth does not
>connect with neutral... it's commom to have about 2volts between
>earth and neutral over here.
That's a European custom - it's not how it's done elsewhere, including
most specifically in North America. The ground and return lead (what
you keep referring to as the 'neutral') MUST BE joined in the
distribution panel. It's a legal requirement here.
>>> a lightning bolt falls in the ground at 6 meters from you and a
>>> cow, you suffer nothing while the cow gets electricuted and
>>> dies... why?
>you don't know why?
No one is interested in games. I assume you are thinking that the
legs of the cow are straddling a potential difference, but that is
equally likely for the person.
>most home ups aren't really ups at all, some of them can't even feed
>the pc after the main power is gone, they are isolation transformers.
Then you should not be buying something from such a fraudulent
supplier. Isolation transformers are not sold as an UPS - which
means Uninterruptable Power Supply. Consult your lawyer.
Old guy
Moe Trin
<4b47d15a$0$270$1472...@news.sunsite.dk>, ArameFarpado wrote:
>Moe Trin escreveu:
>> So by your definition, there can not be a "neutral" in a car or
>> airplane.
>no neutral, cars and planes have a body and one if it's poles is
>connected to the body, usualy the negative pole.
The metallic body (more correctly the frame) is being used as a
conductor. Most cars do not have multiple electrical systems. Planes
with more than one engine ALWAYS do - and even single engine aircraft
often have more than one electrical system. Something like an airliner
will have a minimum of three electrical systems (a legal requirement),
often more. Each has it's own generator or alternator (28 VDC or
115/200 V3Phase400Hz). Some _may_ also have a very limited amount of
50/60 Hz single phase in the lavatories for passenger use.
>planes have a kind of stick that touches he ground (and some cars
>also) to put the body at the same potential as the ground they are
>standing;
I am a commercial airplane pilot, and have had my license for over
30 years. You are absolutely wrong in this statement. There is no
"stick" and never has been - simple mechanical problems like the
compression of the tires, and wind resistance preclude it, never
mind the considerable maintenance issue of constantly replacing it
when it would be knocked off by the ground contact.
>planes must have this or people could get electricuted by touching
>the plane body after a landing...
What is the resistance of the rubber compound used in tires? Assume
an aircraft with a surface area of 350 square meters sitting 2.0
meters off the ground (equivalent to a capacity of ~1600 picofarad)
and a tire resistance of 250 MegOhms. Do you know how to compute
(electrical) discharge time constants? How many seconds will it
take to dissipate a static charge (math: 1 TC ~ 0.25 seconds)?
The only time airplanes are intentionally connected to an electrical
ground is during refueling operations - the plane gets grounded, as
does the fuel truck or hydrant, and a separate ground connection is
made between the fuel hose and the aircraft before the host/nozzle is
allowed to touch the aircraft. This is to prevent static discharges
from causing a spark and igniting the fuel vapo[u]rs.
>some people more sensitive to estatic also place this sticks in
>there cars so they don't get shocked when they touch them or when
>the put the feet on the ground getting out of the car.
Quite a lively imagination you have - same problem as with the
"stick" you claim is on aircraft: compression of the tires as
well as the movement of the suspension system, and the maintenance
issues. It used to be common for fuel trucks to have a length of
steel chain dragging on the ground to discharge any static build-up.
The end of the chain would eventually wear enough to allow the chain
to break, often leaving sharp pieces of metal on the highways. This
discharge function has been transferred to the tires, which are
slightly conductive due to the carbon black material used in creating
the tire. When the fuel trucks are loaded or unloaded, they have the
same grounding wire technique used with aircraft. Next time you see
petrol/gasoline being delivered by truck at a gas/petrol/fuel station
notice the grounding wires connecting the truck and hoses to the
ground lugs.
Old guy
Moe Trin
>Answer One.
Depends on the load, location, and any government requirements. In
most cases it's two.
>The power is returned through the earth, through a ground system.
Maybe in your local conditions - but it's hardly universal. There is
this little variable called "ground resistance" sometimes listed in
a table as "ground constants". In case you aren't aware, there is
well over a 10:1 difference in the conductivity between (for example)
pastoral land with a rich moist soil, and rocky soils and sandy
deserts. There really are areas of the US (and quite a few other
countries) where a 25 foot / 7.6 meter long ground rod will have a
ground resistance in excess of 25 Ohms. Cities, where everything is
paved have similar problems.
Old guy
Moe Trin
<7icm17-...@lapu-lapu.bildanet.com>, GangGreene wrote:
>ArameFarpado wrote:
>>> How many wires from an electical substation to the trasformer on
>>> the pole?
>> 3 life phases, each AC with it's sinosoidal wave lagged 120<C2><BA> to the
>> others. every time 2 phases are positive there is one negative and
>> vice-versa.
>> no need for neutral here.
Depends - is it a three phase star or delta? Stars are nearly always
grounded at the center, while delta may be grounded through a center
tap in one of the legs.
>You are mixed up. I am talking residential power distribution you are
>talking appliance distribution.
You seem to think that the world is all the same as a countryside
district - I'm living in a residential district with no industrial
loads, yet the distribution is three phase 13.2 KV. 'ArameFarpado' is
in Portugal which is in Europe, and it's very common there to
distribute 3 phase in residential areas. Single phase _MAY_ only be
found out in the countryside well away from towns.
>Notice only one leg of the 3 phase is coming down from the overhead 3
>phase lines over head to the xmfr on the pole.
>
>If it was as you believe then two legs of the 3 phase would be in use.
>It's not.
Apparently you also live in an area that doesn't get thunderstorms.
Most of the North American power companies have a "ground" line above
the hot distribution line for lightning protection. This is more
prevalent where the distribution voltage is higher. I've seen places
where 2300 volt lines lack lightning protection, but the more common
13.2 KV has it. One need only look at the high voltage distribution
lines - anywhere from 56 KV (insulators about 18 inches long) on up
to 460 KV (insulators 5 feet or more). These are usually three
phases, and there are one or two uninsulated conductors on the tops
of each pole or tower.
>So tell me why is one leg used on the xfmr and one bare copper line
>going from the xfmr down the pole to a ground rod beside the power
>pole for then?
That's copper clad steel, but no matter. This depends on the location,
the load, and the local regulations. Here (Arizona), there is ALWAYS
a "ground" lead at the top of the pole, and the transformer connects
between the hot lead and that "ground". There may or may not be a wire
coming down the pole and connecting to a ground rod.
>Also when talking polyphase power distribution why then is a grounded
>conductor used/required on the service entrance drop from the pole to
>the residence?
>If it worked as you say it would only require two conductors to be
>brought to the residence.
I'm going to assume you are really this ignorant, and not trolling. The
third wire is used in North America because the standard is two
nominal 120 volt lines with respect to that common. The wire is used
because the resistance of a ground path between your distribution box
and the transformer is at least one and maybe two orders of magnitude
(that is "ten" to "one hundred" times) higher than the resistance of
the "third" wire - call it a neutral or common as you may. Do you
know Ohm's Law? My house has a 300 Amp service (2 120 Volt feeds each
"fused" at 300 Amperes). Assuming even a small inbalance in the load
on the two sides - say 30 Amps - how much power would be lost by not
having a that third wire?
Old guy
Moe Trin
<4b48cda0$0$270$1472...@news.sunsite.dk>, ArameFarpado wrote:
>>>> How many wires from an electical substation to the trasformer on the
>>>> pole?
>substation to transformer is residential distribution? since when?
The terms used in Europe do not match the terms used in the US. Here,
a substation generally means a transformer site where the voltage is
stepped down from the 'cross-country' values (which may be 56KV on up)
to the levels distributed to the neighborhoods (which may be 2300 to
13200 Volts). Separate transformers - either on the local pole, or
on the ground - step the voltage down from this distribution value to
the residential values (120/208 or 120/240) and this is distributed to
one to as many as ten houses. These transformers are not called
sub-stations. Cross-country distribution is almost always 3 phase,
but the neighborhood distribution might be single phase as often as
three phase - depends on how crowded the neighborhood is.
>> So tell me why is one leg used on the xfmr and one bare copper line
>> going from the xfmr down the pole to a ground rod beside the power
>> pole for then?
>aren't you imagining things?
It's not common, but it does occur.
>tri-phasic residential distribution is done with 4 wires: 3 phases
>and 1 neutral, the neutral is necessary for monophasic devices.
Residential use of three phase is rare - it may be found in large
apartment buildings, but even that is rare.
>in europe we have 400volts between phases and 230volts between any
>phase and neutral, if you have 400volts light bolbs then you can
>connect them between 2 phases, but all monophasic devices are
>230volts over here, so the distribution company must provide the
>neutral along with the phases.
Residential use is 120 volts (phase to ground) for all except fixed
appliances (water heater, electric range, electric dryer, central
air conditioners). Those fixed appliances may get 240 volts (an
Edison three-wire system supplied by a center tapped transformer)
or 208 volts (two phases).
>it is also common to see 3 phases and a neutral entering a bilding
>only for monophasic service, that's about balance the phases: 1 phase
>feeds 1/3 of the apartments, the 2nd fase the other 1/3 and the 3rd
>phase feeds the last 1/3 of the apartments.
This does occur, but is not very common. Large apartments are not as
common here.
Old guy
ArameFarpado
you never seen one of these?
http://www.explainthatstuff.com/car_static_strip.jpg
http://www.made-in-china.com/image/3f2j00lMKTGsLgHhoiM/Reflective-Strip-
Static-Belt-with-Light.jpg
ArameFarpado
>
>>> no need for neutral here.
>
> Depends - is it a three phase star or delta? Stars are nearly always
> grounded at the center, while delta may be grounded through a center
> tap in one of the legs.
wait, that's a common error that most people have;
i've seen electricians connect the star point to neutral in triphasic
motors, but that is unnecessary.
any machine that is 100% triphasic (like a commom triphasic motor) don't
need neutral at all, regardless if it is connected in star, delta or zigzag
(this last ir rarely seen and it requires 6 coils instead of 3).
>
> That's copper clad steel, but no matter. This depends on the location,
> the load, and the local regulations. Here (Arizona), there is ALWAYS
> a "ground" lead at the top of the pole, and the transformer connects
> between the hot lead and that "ground". There may or may not be a wire
> coming down the pole and connecting to a ground rod.
same here. that's primary for lightning bolts
ArameFarpado
> On Sat, 09 Jan 2010n the Usenet newsgroup comp.os.linux.hardware, in
> article <4b48cda0$0$270$1472...@news.sunsite.dk>, ArameFarpado wrote:
>
>>>>> How many wires from an electical substation to the trasformer on the
>>>>> pole?
>
>>substation to transformer is residential distribution? since when?
>
> The terms used in Europe do not match the terms used in the US. Here,
> a substation generally means a transformer site where the voltage is
> stepped down from the 'cross-country' values (which may be 56KV on up)
> to the levels distributed to the neighborhoods (which may be 2300 to
> 13200 Volts).
in europe:
high tension
50000volts 3 phases
substation
10000volts 3 phases
transformer post
400volts 3 phases and 230volts each to neutral
in europe a substation receives about 50000volts and lower them to
10000volts
poles for 50000volts
http://thumbs.dreamstime.com/thumb_285/1214983055S25Gbh.jpg
(see the top wire for discharge of thunder bolts)
poles for 10000volts
http://www.danshamptons.com/content/danspapers/issue40_2008/images/FR/lipa.jpg
(they also have top wires for thunder bolts)
> Separate transformers - either on the local pole, or
> on the ground - step the voltage down from this distribution value to
> the residential values (120/208 or 120/240) and this is distributed to
> one to as many as ten houses. These transformers are not called
> sub-stations.
of course not, they are called here: transformation posts
> Cross-country distribution is almost always 3 phase,
> but the neighborhood distribution might be single phase as often as
> three phase - depends on how crowded the neighborhood is.
correct
ArameFarpado
>
>>then every bilding has it's own copper rod, and it's earth does not
>>connect with neutral... it's commom to have about 2volts between
>>earth and neutral over here.
>
> That's a European custom - it's not how it's done elsewhere, including
> most specifically in North America. The ground and return lead (what
> you keep referring to as the 'neutral') MUST BE joined in the
> distribution panel. It's a legal requirement here.
OK
>
>>>> a lightning bolt falls in the ground at 6 meters from you and a
>>>> cow, you suffer nothing while the cow gets electricuted and
>>>> dies... why?
>
>>you don't know why?
>
> No one is interested in games. I assume you are thinking that the
> legs of the cow are straddling a potential difference, but that is
> equally likely for the person.
but the man can stand on the electrified place and not get electricuted if
he doesn't touch nothing eles, like a bird on a wire.
on the other hand, the cow has 2 legs separated about 1 meter from the other
2... right after the falling bolt, the earth absorves the energy and it is
dispersed trought the surrounding area, depending on the position of the cow
related to the place the bolt hitted, the cow can receive a few thousand
volts between it's front legs and rear legs, the shock will cross it's body
stopping it's heart...
this fenomenon have been seen several times in the country; cows, dunkeys,
horses, etc. died in a instant when thunder bolts fall near them.
the all point was about earth's electrical potential, witch is not the same
everywhere.
jellybean stonerfish
> you never seen one of these?
> http://www.explainthatstuff.com/car_static_strip.jpg
>
> http://www.made-in-china.com/image/3f2j00lMKTGsLgHhoiM/Reflective-Strip-
> Static-Belt-with-Light.jpg
>
I've seen these,
http://upload.wikimedia.org/wikipedia/commons/8/85/ManWearingTinFoilHat.jpg
but that doesn't mean one is needed.
Bit Twister
> but the man can stand on the electrified place and not get electricuted if
> he doesn't touch nothing eles, like a bird on a wire.
I disagree. I heard about birds being killed when the power line was
shorted to ground.
Bird, man, or animal are standing upon a conductor (wire, earth).
You can model the circuit which shows they are a parallel resistance
or resistor if you will.
Here R1 would be the wire or earth. R2 would the man,bird,... The + is
each foot's connection to earth/wire.
R2
.--\/\/\/\--.
| |
| R1 |
------+--\/\/\/\--+--------
High values of current passing through the conductor R1 (wire, earth)
create a difference in potential (voltage) due to the resistance of
the conductor R1.
When the potential becomes high enough across R1 enough current will
flow up their feet/legs and through R2 (their body). Once the current
gets high enough in R2's brain/heart death occurs.
no.to...@gmail.com
> Em Quinta 07 Janeiro 2010 08:27, no.to...@gmail.com escreveu:
>
> > In article <4b44e3c5$0$275$1472...@news.sunsite.dk>, ArameFarpado
> > <a-farpa...@netcabo.pt> wrote:
> >
> >> Em Quarta 06 Janeiro 2010 17:23, no.to...@gmail.com escreveu:
> >> > But I can't understand since the UPS is designed to switch on AFTER
> >> > the mains failure.
> >>
> >> wrong.
> >
> > OK, I don't want to influence original contributions, by giving my
> > full present analysis. But the failure process takes a finite time.
> > And I insist that the UPS can only acts AFTER the beginning of the
> > mains 'failure process'.
> >
> > Can you contribute more than "wrong" ?
>
> You are confusing a UPS with a emergency electric generator; those are the
> ones that start working after the power goes off.
> A UPS needs to keep the power up without letting it go down even for a split
> second.
>
Let's be more scientific: at 50 Hz, there are zero-crossings every 10 ms.
> The only switch a ups does when the power goes off is that it stops charging
> the batteries. The output of a UPS is allways given by the same circuits
> regardless if the power is on or off
>
> with power on:
>
> main power -> AC-DC converter -> DC-AC converter -> output
> -> charge batteries.
>
> with power off:
>
> batteries -> DC-AC converter -> output
>
> this is the only way that an ups can keep the output on without any breaks.
So the computer is fed from the UPS *always*,
and the "switch over is only from (accum to ) or (mains to D2A) ?
M-A2D-D2A->C
----B-D2A->C
>
> so resuming: if the ups's output is given the wrong voltage, frequency,
> sinosoidal wave, etc... you have two choices:
> 1- repair the ups
> 2- replace the ups.
>
What did I write to suggest that "the ups's output is given the wrong" output ?
How would that cause the earth-leakage to activate ?
============
philo wrote:
> So the conclusion is reversed from what has happened
>
> It was a ground fault which *caused* the power interruption.
>
> The UPS simply was on because the "mains" breaker had tripped
No it's a chain of events over a few milliseconds.
The UPS detects that the mains is 'abnormal' and switches;
which causes an earth-leakage abnormality.
My problem is that since the earth-leakage AFAIK is mechanical,
it should not react to the spike caused by the UPS.
What are typical earth leakage response times?
=============
> if you have electrical questions, it's better to put them in
> sci.electronics.basics
yes, the boys here are just guessing.
>i can tell you that if you desconnect the earth, ther will be no more a
>neutral in the output, you will have two live lines with a voltage
>between them, and that could cause other issues.
Yes disabling the earth-leakage-detector is not good.
==========
> > so resuming: if the ups's output is given the wrong voltage, frequency,
> > sinosoidal wave, etc... you have two choices: 1- repair the ups
> > 2- replace the ups.
david wrote:-
> This is only true with a double-conversion type UPS, which most cheap PC-
> type UPS's are not. Most cheap UPSs have a transfer switch in them, so
> the power is actually interrupted for a few milliseconds when the mains
> fail.
>
Yes, I'd expect the computer PSU to 'hold over' for 2 cycles: 20 ms.
It seems that none of you are considering the interaction back to the
earth-leakage ?
== Thanks for any reasoned answers [not guesses].
ArameFarpado
for that to work the way you say, the conductor must be highly damage right
under the bird/man feet.
Curt
> this fenomenon have been seen several times in the country; cows, dunkeys,
> horses, etc. died in a instant when thunder bolts fall near them.
Is this an argument for bipedalism?
> the all point was about earth's electrical potential, witch is not the same
> everywhere.
I think we have more potential here in Europe, but that's just me.
jellybean stonerfish
> the all point was about earth's electrical potential, witch is not the
> same everywhere.
>
>
I agree that witches are not the same everywhere, but what does that have
to do with electrical potential.
Bit Twister
>>
>> Here R1 would be the wire or earth. R2 would the man,bird,... The + is
>> each foot's connection to earth/wire.
>>
>> R2
>> .--\/\/\/\--.
>> | |
>> | R1 |
>> ------+--\/\/\/\--+--------
>>
>>
>> High values of current passing through the conductor R1 (wire, earth)
>> create a difference in potential (voltage) due to the resistance of
>> the conductor R1.
>>
>> When the potential becomes high enough across R1 enough current will
>> flow up their feet/legs and through R2 (their body). Once the current
>> gets high enough in R2's brain/heart death occurs.
>
> for that to work the way you say, the conductor must be highly damage right
> under the bird/man feet.
Absolutely not. Under normal conditions no conductor is resistance free.
The operational factor here is the very high abnormal current flow
between points of contact creating the voltage.
ArameFarpado
even high tension cables have circuit breakers that shuts down lines in
short circuit
Bit Twister
> even high tension cables have circuit breakers that shuts down lines in
> short circuit
Did not say they didn't. Of course they are slow blow breakers giving
time for the fatal shock to kill the birds.
david
to say:
> Guys/Gals Please
>
> One question....
>
> How many wires from an electical substation to the trasformer on the
> pole?
>
> Answer One.
>
> There is no neutral.
> The power is returned through the earth, through a ground system.
Clearly you have no knowledge how an electric disribtion system works.
In a delta-connected system, there is no neutral. In a wye-connected
system the neutral point is the common point where all three phases are
tied together. If the three phases are balanced, there will be no net
current and thus no voltage at the neutral point. Since the phases are
rarely perfectly balanced, there is usually some voltage at the neutral
point.
A typical premises distribution transformer in the US will step down one
single phase of a three-phase delta (or wye) transformer primary to 240V
across two lines. The neutral is a center tap from the secondary
winding, and is bonded to earth ground in the service entrance panel, per
the US National Electric Code.
If your house (or business) has 3-phase power, it is usually a 4-wire
(wye) system. The secondary side of the transformer is connected as a
wye, which means the neutral is the common point of the three windings.
Per US code, the neutral must be bonded to earth ground at the service
entrance.
GangGreene
> On Fri, 08 Jan 2010 20:12:39 -0500, GangGreene rearranged some electrons
> to say:
>
>
>> Guys/Gals Please
>>
>> One question....
>>
>> How many wires from an electrical substation to the transformer on the
>> pole?
>>
>> Answer One.
>>
>> There is no neutral.
>> The power is returned through the earth, through a ground system.
>
> Clearly you have no knowledge how an electric distribution system works.
Ah yes you are correct, that is why I have been a controls engineer for 25
years at a very large retail company.
>
> In a delta-connected system, there is no neutral.
Not so, you could have a corner grounded delta. One could also have a 4 wire
delta system.
> In a wye-connected system the neutral point is the common point where all
> three phases are tied together.
There is a common point but I don't it's required to be connected to ground.
I will have to look it up in my NEC book.
You also don't need to use the common point wire.
It is a common point but really not a neutral.
Remember a neutral is only a reference point, which is useally tied to
ground.
I have seen corner grounded wye installations. Now what?
> If the three phases are balanced, there
> will be no net
> current and thus no voltage at the neutral point. Since the phases are
> rarely perfectly balanced, there is usually some voltage at the neutral
> point.
Both reactively and resistance balanced of course.
Power factors being involved.
>
> A typical premises distribution transformer in the US will step down one
> single phase of a three-phase delta (or wye) transformer primary to 240V
> across two lines. The neutral is a center tap from the secondary
> winding, and is bonded to earth ground in the service entrance panel, per
> the US National Electric Code.
It is not a neutral at the pole, just a simple center tapped xfmr with both
ends out of phase with respect to the center tap point (ie the reference
point).
It only becomes a neutral at the service panel.
>
> If your house (or business) has 3-phase power, it is usually a 4-wire
> (wye) system. The secondary side of the transformer is connected as a
> wye, which means the neutral is the common point of the three windings.
Doesn't have to be 4 wire could be 3 wire wye connection.
> Per US code, the neutral must be bonded to earth ground at the service
> entrance.
Now what about 13.2 KV service to a building?
Care to comment on that?
Do you know what a switch gear is?
Moe Trin
<4b4a5884$0$278$1472...@news.sunsite.dk>, ArameFarpado wrote:
>Bit Twister escreveu:
>>ArameFarpado wrote:
[Bit Twister wrote:]
>>>> Once the current gets high enough in R2's brain/heart death occurs.
Well, let's just say that significant problems occur with R2, whether
it be a bird, cow, human, or some electronics.
>>> for that to work the way you say, the conductor must be highly
>>> damage right under the bird/man feet.
No.
>> Absolutely not. Under normal conditions no conductor is resistance
>> free
Oh, like you mean the ground between the {bird|cow|person}s legs?
Yeah - had a problem like that happen. A lightning strike hit the
ground several hundred {feet|meters} away from an aircraft landing
guidance transmitter. The transmitter, transmitting antenna, and
associated electronics in one building with _three_ 25 foot/7.6 meter
long ground rods (two for lightning rods, one for the power/electronics)
and the "monitor" antenna on a stub mast 100 foot/30 meters away with
two more of those long ground rods (one for the mast, one for the
electronics). The distance from the strike to the two sites was not
equal, and we had differential ground voltages because of it. The
monitor (video) signals were protected by lightning arrestors (spark
gap and Surgistors) at BOTH ends of the wire. The protection apparently
worked, but the video leads from the monitor exceeded the common mode
input voltage limits (~25 Volts?) and toasted the op-amps. May well
have been a dV/dT issue. Lightning waveforms usually have a pretty
ferocious rise-time.
>> The operational factor here is the very high abnormal current flow
>> between points of contact creating the voltage.
Lightning strikes are often (theoretically) measured in kilo-amperes
>even high tension cables have circuit breakers that shuts down lines
>in short circuit
I haven't seen circuit breakers on the source of lightning bolts.
In any case, how fast can they react?
Old guy
GangGreene
[putolin]
>
> Oh, like you mean the ground between the {bird|cow|person}s legs?
> Yeah - had a problem like that happen. A lightning strike hit the
> ground several hundred {feet|meters} away from an aircraft landing
> guidance transmitter. The transmitter, transmitting antenna, and
> associated electronics in one building with _three_ 25 foot/7.6 meter
> long ground rods (two for lightning rods, one for the power/electroni
I have seen contractors installing radio antennas/towers hire water well
drillers to dig and case wells just for use as ground rod for lightning
protection. The well is not meant to produce water only to serve as a huge
ground rod, 8 inches in diameter and a hundred feet down.
david
to say:
> david wrote:
>
>> On Fri, 08 Jan 2010 20:12:39 -0500, GangGreene rearranged some
>> electrons to say:
>>
>>
>>> Guys/Gals Please
>>>
>>> One question....
>>>
>>> How many wires from an electrical substation to the transformer on the
>>> pole?
>>>
>>> Answer One.
>>>
>>> There is no neutral.
>>> The power is returned through the earth, through a ground system.
>>
>> Clearly you have no knowledge how an electric distribution system
>> works.
>
> Ah yes you are correct, that is why I have been a controls engineer for
> 25 years at a very large retail company.
>
>
>> In a delta-connected system, there is no neutral.
>
> Not so, you could have a corner grounded delta. One could also have a 4
> wire delta system.
A corner grounded delta still does not contain a neutral.
>
>> In a wye-connected system the neutral point is the common point where
>> all three phases are tied together.
>
> There is a common point but I don't it's required to be connected to
> ground. I will have to look it up in my NEC book. You also don't need to
> use the common point wire.
See section 250.
>
> It is a common point but really not a neutral. Remember a neutral is
> only a reference point, which is useally tied to ground.
>
> I have seen corner grounded wye installations. Now what?
That doesn't make any sense.
>
>
>> If the three phases are balanced, there will be no net
>> current and thus no voltage at the neutral point. Since the phases are
>> rarely perfectly balanced, there is usually some voltage at the neutral
>> point.
>
> Both reactively and resistance balanced of course. Power factors being
> involved.
>
>
>> A typical premises distribution transformer in the US will step down
>> one single phase of a three-phase delta (or wye) transformer primary to
>> 240V across two lines. The neutral is a center tap from the secondary
>> winding, and is bonded to earth ground in the service entrance panel,
>> per the US National Electric Code.
>
> It is not a neutral at the pole, just a simple center tapped xfmr with
> both ends out of phase with respect to the center tap point (ie the
> reference point).
>
> It only becomes a neutral at the service panel.
No, it only becomes BONDED (a grounded neutral) at the service panel.
It's still neutral.
>
>
>> If your house (or business) has 3-phase power, it is usually a 4-wire
>> (wye) system. The secondary side of the transformer is connected as a
>> wye, which means the neutral is the common point of the three windings.
>
> Doesn't have to be 4 wire could be 3 wire wye connection.
>
>> Per US code, the neutral must be bonded to earth ground at the service
>> entrance.
>
> Now what about 13.2 KV service to a building? Care to comment on that?
>
> Do you know what a switch gear is?
13.2kv service to a building is most likely delta.
Greegor
AF > you never seen one of these?
http://www.explainthatstuff.com/car_static_strip.jpg
Did you notice that it's not touching ground?