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Sci.Electronics.Basics -> Surge / Ground / Lightning
There are 215 messages in this thread.
You are currently looking at messages 140 to 160.
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Author: Michael A. TerrellDate: 12:08 06-05-08
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w_tom wrote:
>
> On May 4, 9:09 pm, "Michael A. Terrell"
<mike.terr...@earthlink.net>
> wrote:
> > The same thing we did in the studios and transmitter sites. Use a
> > combination of protection at the building's main disconnect, and
> > individual protection at each critical device. The only thing that I've
> > lost in the last ten years was when lightning hit a huge pine tree, and
> > cut the top half of it off. It landed on the ground right over the
> > buried telephone line, and a second strike blew out the modem and MOV
> > protection on the phone line.
>
> You suffered damage from a lightning strike and call that effective
> protection? Modems are most typically damaged by surges entering an
> AC mains. Outgoing surge path would be the phone line to earth via a
> telco installed 'whole house' protector. Damage from lightning is
> effective protection? After spending how much for all those
> protectors, you call that protection?
Where did I say HOW was protected? It was my second week at that
station, and the chief engineer took off on a long overdue vacation. If
you would learn to read, rather than just do mindless rants you wouldn't
look so stupid. At that time the building had a UFER ground, and a
three phase protection system at the meter CTs. That didn't prevent the
damage, as you claim it should.
> Phone lines do not use MOV protectors. Basic information that you
> would have learned if not wasting time insulting people.
Sorry, _wacko_ but you are the one slinging insults and ignoring
proof from hundreds of people.
> MOVs have
> too much capacitance. Phone line 'whole house' protectors use other
> technologies with lower capacitance.
Gee, _wacko_ you've never seen ANY modern business telephone
equipment? Gas tubes are fragile and very expensive. The protection
isn't to save the privately owned telephones, it it to limit damage to
the building. Even that mid '60s 1A2 system had every output of the
power supply fused to prevent a fire. Explain why an MOV's capacitance
is high enough to affect a phone line. Never mind. I have a Nitsuko/NEC
DX2NA-32SYTEMEM KEY TELEPHONE SYSTEM in front of me, and every CO line
in it has a MOV across the line. Once more, you're preaching lies and
using deceit to try to make others look bad.
,http://refurbishednitsuko.net/productInfo.aspx?productID=75978489-9ac8-40c1-9496-559bfc
01b4d3>
is the Central Office line card for four telephone lines. See the black
MOVs to the right of each pair of fuses?
<http://refurbishednitsuko.net/productInfo.aspx?productID=f5453e33-047e-4726-8631-50a
929aabedf>
is the card for four standard 2500 type telephones, or equivalent
equipment. See the pairs of black MOVs over the blue connectors at the
bottom of the screen? They are all japanese, with no brand markings.
<http://www.epcos.com/web/generator/Web/Sections/Publications/PDF/SIOVMetalOxideVaris
tors,property=Data__en.pdf;/SIOVMetalOxideVaristors.pdf>
is the Epcos MOV databook, with datasheets for Telecom applications.
page 213 list the TELECOM MOV data.
Every line into that studio building had a long distance call device
diverter in the line that had MOV across the phone line. Every one of
them survived the direct hit to the building and STL tower. That's more
than can be said of your ability to use reason, and learn new things.
You need to get your head out of 1920 and learn modern electronics.
The one thing we learned today is that you don't know any more about
Telecom that you do lightning protection, or reading comprehension.
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Author: bud--Date: 12:18 06-05-08
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phil-news-nospam@ipal.net wrote:
> In alt.engineering.electrical bud-- <remove.budnews@isp.com> wrote:
> | phil-news-nospam@ipal.net wrote:
> |> In alt.tv.tech.hdtv bud-- <remove.budnews@isp.com> wrote:
>
> |> | w_' professional engineer source says 8 micoseconds with most of the
> |> | spectrum under 100kHz.
> |>
> |> Even with 1 nanosecond rise time, most of the energy will be present in
> |> the spectrum below 100 kHz. That means nothing when the surge is strong
> |> enough to have energy above some frequency that is relevant to the whole
> |> system involved that can do damage. That frequency might be 100 Mhz for
> |> some thing, and 1 GHz for other things.
> |
> | Still missing - your source. Nanosecond risetime. 100MHz spectrum.
>
> Observation. Of course this is a concept you cannot understand.
Observation proves flying saucers and magic.
Without supporting sources it is Phil's Phantasy Physics.
Where is a source that supports your belief in nanosecond risetimes and
100MHz spectrum?
--
bud--
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Author: bud--Date: 12:20 06-05-08
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phil-news-nospam@ipal.net wrote:
> In alt.engineering.electrical Don Kelly <dhky@shaw.ca> wrote:
>
> | Now - is this all germane to household protection? You say not and I agree
> | with you- because household equipment can ride through - at worst- doubling
> | of the clamped voltage for a very short time even though the clamped voltage
> | is relatively small compared to the peak of the incoming surge. --
>
> My belief is that they
> can, and will at times.
People believe in flying saucers.
Where is a source that supports your belief?
>
> I do agree that things can survive at the clamping voltage. But there has to
> be a clamping situation. It's too easy for a surge to come in as a common
> mode surge where the voltage difference across the MOVs would be (nearly) zero.
> Then all we have is a propogating wavefront. And if it is strong and/or close
> then we have very fast rise times. And it passes by the MOVs
"laterally".
Where is a source that supports your belief in nanosecond risetimes and
100MHz spectrum?
> But one thing I do see in at least part of this thread is that Bud
> focuses on quoting things other people say, and does very little to express
> things in his own words.
I focus on the real world. You focus on your beliefs.
Where is a source that supports your belief in nanosecond risetimes and
100MHz spectrum?
--
bud--
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Author: bud--Date: 12:37 06-05-08
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w_tom wrote:
> On May 5, 2:35 pm, bud-- <remove.budn...@isp.com> wrote:
>> The IEEE guide is aimed at "electricians, architects, technicians, and
>> electrical engineers who were not protection specialists."
>
> Industry standard facts and
> embarrassing questions.that Bud will ignore to lie and to promote plug-
> in protector sales
Lacking any valid technical arguments poor w_ has to try to discredit
opponents. My only association with surge protectors is I have some.
>
> 1) How does that plug-in protector provide protection without the
> 'always necessary' earth ground? What does a protector do? Bud
> provides only two citations. Both disagree with his claims. The NIST
> bluntly defines what a protector must do - Page 6:
What does the NIST guide really say about plug-in suppressors?
They are "the easiest solution".
>
> 2) Bud not only denies this also so important single point earth
> ground.
If w_ could only read he would have seen my emphasis on a *short*
'ground' wire from phone/cable entry protectors to the 'ground' at the
power service. w_ appears to want all wires run to the grounding
electrode. That does not provide the minimum voltage between power and
signal wires. Martzloff has written "the impedance of the grounding
system to 'true earth' is far less important than the integrity of the
bonding of the various parts of the grounding system."
And the case where phone/cable entry points are too far distant from
power service, IEEE guide says "the only effective way of protecting
the equipment is to use a multiport [plug-in] protector."
> He also ignores what happens when a protector is too far from
> earth and too close to appliances. Page 42 Figure 8: the surge
> earthed 8000 volts destructively through appliances. This is the
> second point from his citations that Bud must ignore.
The illustration has 2 TVs. The IEEE says the point of the illustration
is "to protect TV2, a second multiport protector located at TV2 is
required." Way to complicated for w_.
>
> 3) So if a plug-in protector is effective protection, then
> manufacturer specs will list each type of surge and protection from
> that surge. Bud never provides that spec either.
"Each type of surge" is nonsense. w_'s favored SquareD service panel
suppressors do not have specs for "each type of surge". Lacking valid
technical arguments has to invent problems.
> Plug-in
> protectors don't claim to protect from the type of surge that
> typically causes damage.
Complete nonsense.
> Not one plug-in protector manufacturer will
> claim that protection - made obvious because Bud will not post those
> specs and ignored over 400 requests for those specs.
Over 400 requests - another hallucination.
Specs posted often and ignored.
>
> 4) No earth ground means no effective protection. A protector is
> only as effective as its earth ground.
w_'s religious belief (immune from challenge) in earthing has been the
elephant in the closet. w_ believes a surge protector must directly
earth a surge. Thus in his view plug-in suppressors (which are not well
earthed) can not possibly work.
The IEEE guide explains plug-in suppressors work by CLAMPING the voltage
on all wires (signal and power) to the common ground at the suppressor.
The voltage between the wires going to the protected equipment is safe
for the protected equipment. Plug-in suppressors do not work primarily
by earthing (or stopping or absorbing). The guide also explains earthing
does occur, just not primarily through the plug-in suppressor. (Read the
guide starting pdf page 40).
For accurate information on surges read the IEEE and NIST guides. Both
say plug-in suppressors are effective.
There are 98,615,938 other web sites, including 13,843,032 by lunatics,
and w_ can't find another lunatic that says plug-in suppressors are NOT
effective. All you have is w_'s opinions based on his religious belief
in earthing.
Embarrassing questions that w_ will ignore:
- Why do the only 2 examples of surge suppression in the IEEE guide use
plug-in suppressors?
- Why does the NIST guide says plug-in suppressors are "the easiest
solution"?
- Why do all but one of w's "responsible manufacturers" make plug-in
suppressors?
- Why does SquareD say in addition to their "whole house" suppressors
"electronic equipment may need additional protection" from plug-in
suppressors.
- Why aren't airplanes crashing daily when they get hit by lightning (or
do they drag an earthing chain)?
--
bud--
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Author: bud--Date: 12:39 06-05-08
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w_tom wrote:
> On May 5, 2:27 pm, Mike Tomlinson <m...@jasper.org.uk> wrote:
>> It is those nuances that w_twat fails to explain when he spouts his one-
>> cure-for-all-ills religious mantra about every dwelling absolutely
>> requiring whole-house surge protection.
>
> Mike Tomlinson has just posted in agreement. UK homes typically do
> not need what is necessary in FL homes. UK homes need not be earthed
> as central FL homes may be earthed:
> http://members.aol.com/gfretwell/ufer.jpg
>
> Many homes have more than enough protection with only one earthed
> 'whole house' protector - and nothing else. Especially in the UK.
> That means spending tens (or maybe one hundred) times less money for
> protection of everything.
>
> UK homes may be more than sufficiently earthed with one 3 meter
> ground rod. Then one surge protector can provide more than sufficient
> protection for everything - eliminating maybe £500 or £2000 for plug-
> in protectors.
Last I heard UK phone entry protectors did not clamp the voltage to
earth. That allows high voltage between power and phone wires. w_’s
favored service panel suppressor provides no protection from this hazard.
--
bud--
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Author: bud--Date: 12:40 06-05-08
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Don Kelly wrote:
> ----------------------------
> "bud--" <remove.budnews@isp.com> wrote in message
> news:e234c$481f53e8$4213eabe$21042@DIALUPUSA.NET... />
>> Don Kelly wrote:
>>> ----------------------------
>>> "Tony Hwang" <dragon40@shaw.ca> wrote in message
>>> news:dncTj.112858$rd2.31639@pd7urf3no...
>>>> phil-news-nospam@ipal.net wrote:
>>>>> In alt.tv.tech.hdtv Michael A. Terrell
<mike.terrell@earthlink.net>
>>>>> wrote:
>>>>>
>>>>> | Bullshit. Like ALL charges, it simply seeks a complete circuit
to
>>>>> | flow. You have absolutely no grasp of the basic concepts, yet
you
>>>>> | continue to spout your ignorance and lies.
>>>>>
>>>>> Not true.
>>>>>
>>>>> When you close a switch between a power source and a pair of wires
that
>>>>> go
>>>>> out yonder, the electrical energy does not "know" whether
the circuit
>>>>> is
>>>>> complete or not. If it refused to flow, it would not be able to
find
>>>>> out.
>>>>> It will flow, whether the circuit is complete or not. What happens
>>>>> after
>>>>> that depends on what is at the other end, which could be an open
>>>>> condition,
>>>>> a short circuit, or some kind of resistive or reactive load.
>>>>>
>>>>> You've claimed to have worked in broadcasting in an engineering
role.
>>>>> So
>>>>> you should understand what happens at the end of an open
transmission
>>>>> line.
>>>>> The electricity flows to get to the open end. Yet it is not a
>>>>> "complete
>>>>> circuit".
>>>>>
>>>> Hmmm,
>>>> You seem to be confused between current flow(energy) and
>>>> voltage(poential) Nothing flows in an open circuit. If not we have to
>>>> rewrite Ohm's law. Show your credential to make a stamement like that.
>>>> Shameful.
>>> ------------------------
>>> Actually, you are showing some confusion. Phil is right in that he is
>>> bringing out a point that normal lumped RLC circuit theory doesn't handle
>>> because it essentially treats the speed of propagation of electrical
>>> signals as if it were infinite- which isn't true.
>>> .
>>> 2)Also, on energizing a line whether it is open or closed, there is a
>>> current flow as the applied voltage "sees" the characteristic
impedance
>>> of the line (wire or whatever) so a current will flow-even on an open
>>> circuit- until there is a modifying reflection from the termination. For
>>> a house the distances are such that this may be of the order of 0.1-0.2
>>> microsecond. After all such reflections at terminations have ceased or
>>> are negligable, conventional circuit theory is applicable.
>>> In these situations, you are dealing with wave propagation rather than
>>> conventional circuit theory.
>>> This is the regime that is of interest in considering "surge
protectors"
>> The last standards for simulating typical surge waveforms I have seen
>> (IEEE) were
>> 1.2 us rise time, 50 us duration
>> 8 us rise time, 20 us duration
>> a ring wave with a frequency about 100kHz.
>>
>> All are long relative to 0.2 microsecond, so wave propagation should not
>> be relevant for household circuits.
> ----------------------------------------
> Your point is true- the time interval is so small that for practical
> purposes it can be ignored. I am not denying that. Obviously I gave that
> impression- sorry for that.
>
> I was simply pointing out that phil had it right in theory and Tony had it
> wrong.
>
> After this time for the wave to travel to the end and be reflected (and
> other re-reflections die out) then conventional circuit theory is
> applicable. The fact that the time is extremely small simply means that we
> can pretend that it doesn't even exist.
>
> While Matzloff is right in the time for a round trip is of the order of
> 200m, it is also dangerous to assume that one can ignore waves for shorter
> distances. For example, a stroke to a tower of an EHV line (a lot less than
> 200m) will go down the tower, meet ground resistance and be reflected.
> Such reflections have been found to be more likely to cause flashover than
> direct strokes to the line (EPRI). Similarly, the practice in substations
> is not "whole station" protection (where this is applicable, it must be
done
> considering a number of factors- quite interesting ) and putting specific
> protection as near as possible to the protected apparatus-definitely within,
> say, 10m. - It's not just the time to peak that is the critical factor. Do a
> lattice diagram approach or use Bergeron's method (Hermann Dommel did a lot
> of work with this at EPRI and has a lot of papers in IEEE- more dealing with
> switching surges than lightning).
> It's been a long time since I did any calculations in this area so I would
> have to brush up.
I am real glad the probability of a direct house strike is low. I have
some appreciation for the earthing/bonding required in a substation
(also referred to by nobody).
>
> Now - is this all germane to household protection? You say not and I agree
> with you- because household equipment can ride through - at worst- doubling
> of the clamped voltage for a very short time even though the clamped voltage
> is relatively small compared to the peak of the incoming surge. --
The effect Martzloff was specifically looking for in experiments was
doubling of voltage.
As an aside, several of the experiments done by Martzloff were at EPRI.
--
bud--
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Author: Phil HowardDate: 12:50 06-05-08
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In alt.engineering.electrical bud-- <remove.budnews@isp.com> wrote:
| phil-news-nospam@ipal.net wrote:
|> In alt.engineering.electrical bud-- <remove.budnews@isp.com> wrote:
|> | phil-news-nospam@ipal.net wrote:
|> |> In alt.tv.tech.hdtv bud-- <remove.budnews@isp.com> wrote:
|>
|> |> | w_' professional engineer source says 8 micoseconds with most of the
|> |> | spectrum under 100kHz.
|> |>
|> |> Even with 1 nanosecond rise time, most of the energy will be present in
|> |> the spectrum below 100 kHz. That means nothing when the surge is strong
|> |> enough to have energy above some frequency that is relevant to the whole
|> |> system involved that can do damage. That frequency might be 100 Mhz for
|> |> some thing, and 1 GHz for other things.
|> |
|> | Still missing - your source. Nanosecond risetime. 100MHz spectrum.
|>
|> Observation. Of course this is a concept you cannot understand.
|
| Observation proves flying saucers and magic.
|
| Without supporting sources it is Phil's Phantasy Physics.
| Where is a source that supports your belief in nanosecond risetimes and
| 100MHz spectrum?
Since you seem unwilling to just discuss technical aspects of things, I have
to conclude that you simply do not understand what it is you read and quote.
Too many times you quote out of context. I don't know where that is because
you are trying to be manipulative or simply on account of ignorance. There
is that old sayind "Do not ascribe to malice that which can be explained by
ignorance". I don't know if I should follow it's advice.
There is no point in spending the effort to find some quotable source because
you wouldn't know what to do with it. How could you possibly comprehend what
I would give you if you can't even comprehend what you post.
After this round of followups, I'm done with this thread and I'm done replying
to you. If curing your ignorance is in your future, it will have to be from
someone else.
--
|WARNING: Due to extreme spam, I no longer see any articles originating from |
| Google Groups. If you want your postings to be seen by more readers |
| you will need to find a different place to post on Usenet. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |
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Author: Phil HowardDate: 12:57 06-05-08
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In alt.engineering.electrical Eric <me@nomail.com> wrote:
| I can attest to vhf/uhf content in lightning strikes. I worked for a
| communications outfit. We owned and maintained a number of comm sites
| with towers and antennas. One strike on an antenna destroyed the LDF rf
| cable all the way to the polyphaser at the bottom of the tower. It had
| blowouts at about 1 foot intervals all down it's length suggesting a
| 1/2 wave of about 1 foot or approx 460 mhz. That's one hell of a lot of
| energy at that frequency..
Apparently you had some kind of resonance involved. Maybe the antenna itself
can cause that. Or the output tank circuit in the transmitter. Once you have
the resonance to narrowband the energy, it would only take a reflection back
up the line and you turn a propogating surge into standing waves.
--
|WARNING: Due to extreme spam, I no longer see any articles originating from |
| Google Groups. If you want your postings to be seen by more readers |
| you will need to find a different place to post on Usenet. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |
|
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Author: Phil HowardDate: 13:05 06-05-08
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In alt.engineering.electrical bud-- <remove.budnews@isp.com> wrote:
| phil-news-nospam@ipal.net wrote:
|> In alt.engineering.electrical Don Kelly <dhky@shaw.ca> wrote:
|>
|> | Now - is this all germane to household protection? You say not and I agree
|> | with you- because household equipment can ride through - at worst- doubling
|> | of the clamped voltage for a very short time even though the clamped voltage
|> | is relatively small compared to the peak of the incoming surge. --
|>
|> My belief is that they
|> can, and will at times.
|
| People believe in flying saucers.
| Where is a source that supports your belief?
My observations support my belief. I don't expect YOU to believe it on the
basis if MY observations, as I certainly won't believe things on the basis
of YOUR observations. What I am posting about is for you to UNDERSTAND what
I believe, not that you have to believe it. Maybe someday you will come to
understand it, and then you might realize how you have misread what it is
you have been quoting online.
Since you spend all your keystrokes making person attacks or insisting on
something being cited, or make quotes that are often truncated incorrectly
or misapplied, I can only conclude you have no actual understanding of what
it is you have been quoting. What good would me citing anything do for you
if you can't understand it.
|> I do agree that things can survive at the clamping voltage. But there has to
|> be a clamping situation. It's too easy for a surge to come in as a common
|> mode surge where the voltage difference across the MOVs would be (nearly) zero.
|> Then all we have is a propogating wavefront. And if it is strong and/or close
|> then we have very fast rise times. And it passes by the MOVs
"laterally".
|
| Where is a source that supports your belief in nanosecond risetimes and
| 100MHz spectrum?
Another poster followed up to my post you just followed up to that also has
experienced the same thing. That might not be some published citation that
you want. But that doesn't matter. It seems you can't comprehend what this
is about regardless of whether it is observed by others, or yourself, or by
the experts you cite.
|> But one thing I do see in at least part of this thread is that Bud
|> focuses on quoting things other people say, and does very little to express
|> things in his own words.
|
| I focus on the real world. You focus on your beliefs.
You focus on citing and quoting things you do not understand well enough to
just talking about them in technical terms.
| Where is a source that supports your belief in nanosecond risetimes and
| 100MHz spectrum?
See above.
And after this round of followups, I'm done with this thread and with your
posts on this subject. You can have the last say, but I will not even read
it.
--
|WARNING: Due to extreme spam, I no longer see any articles originating from |
| Google Groups. If you want your postings to be seen by more readers |
| you will need to find a different place to post on Usenet. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |
|
|
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Author: EricDate: 13:08 06-05-08
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phil-news-nospam@ipal.net wrote:
> In alt.engineering.electrical Eric <me@nomail.com> wrote:
>
> | I can attest to vhf/uhf content in lightning strikes. I worked for a
> | communications outfit. We owned and maintained a number of comm sites
> | with towers and antennas. One strike on an antenna destroyed the LDF rf
> | cable all the way to the polyphaser at the bottom of the tower. It had
> | blowouts at about 1 foot intervals all down it's length suggesting a
> | 1/2 wave of about 1 foot or approx 460 mhz. That's one hell of a lot of
> | energy at that frequency..
>
> Apparently you had some kind of resonance involved. Maybe the antenna itself
> can cause that. Or the output tank circuit in the transmitter. Once you have
> the resonance to narrowband the energy, it would only take a reflection back
> up the line and you turn a propogating surge into standing waves.
>
Pretty much what we determined. Also in another thread I stressed that
the rise time by itself does not determine frequency content. One needs
to know the rate of change, or slew rate, to determine that. A
lightning pulse may have a rise time of 1.2 microseconds but in that
short time the current can rise to thousands of amps, generating a large
amount of vhf,uhf energy.
Eric
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Author: Sjouke BurryDate: 14:45 06-05-08
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On May 6, 12:08=A0pm, "Michael A. Terrell" <mike.terr...@earthlink.net>
wrote:
> w_tom wrote:
>
> > On May 4, 9:09 pm, "Michael A. Terrell"
<mike.terr...@earthlink.net>
> > wrote:
> > > =A0 =A0The same thing we did in the studios and transmitter sites. =A0=
Use a
> > > combination of protection at the building's main disconnect, and
> > > individual protection at each critical device. =A0The only thing that =
I've
> > > lost in the last ten years was when lightning hit a huge pine tree, an=
d
> > > cut the top half of it off. It landed on the ground right over the
> > > buried telephone line, and a second strike blew out the modem and MOV
> > > protection on the phone line.
>
> > =A0 You suffered damage from a lightning strike and call that effective
> > protection? =A0Modems are most typically damaged by surges entering an
> > AC mains. =A0Outgoing surge path would be the phone line to earth via a
> > telco installed =A0'whole house' protector. =A0Damage from lightning is
> > effective protection? =A0After spending how much for all those
> > protectors, you call that protection?
>
> =A0 =A0Where did I say HOW was protected? It was my second week at that
> station, and the chief engineer took off on a long overdue vacation. If
> you would learn to read, rather than just do mindless rants you wouldn't
> look so stupid. =A0At that time the building had a UFER ground, and a
> three phase protection system at the meter CTs. That didn't prevent the
> damage, as you claim it should.
>
> > =A0 Phone lines do not use MOV protectors. =A0Basic information that you=
> > would have learned if not wasting time insulting people.
>
> =A0 =A0Sorry, _wacko_ but you are the one slinging insults and ignoring
> proof from hundreds of people.
>
> > =A0MOVs have
> > too much capacitance. =A0Phone line 'whole house' protectors use other
> > technologies with lower capacitance.
>
> =A0 =A0Gee, _wacko_ you've never seen ANY modern business telephone
> equipment? =A0Gas tubes are fragile and very expensive. The protection
> isn't to save the privately owned telephones, it it to limit damage to
> the building. =A0Even that mid '60s 1A2 system had every output of the
> power supply fused to prevent a fire. Explain why an MOV's capacitance
> is high enough to affect a phone line. Never mind. =A0I have a Nitsuko/NEC=
> DX2NA-32SYTEMEM KEY TELEPHONE SYSTEM in front of me, and every CO line
> in it has a MOV across the line. =A0Once more, you're preaching lies and
> using deceit to try to make others look bad.
>
> ,http://refurbishednitsuko.net/productInfo.aspx?productID=3D75978489-9ac..=
.>
> is the Central Office line card for four telephone lines. See the black
> MOVs to the right of each pair of fuses?
>
> <http://refurbishednitsuko.net/productInfo.aspx?productID=3Df5453e33-047..=
.>
> is the card for four standard 2500 type telephones, or equivalent
> equipment. See the pairs of black MOVs over the blue connectors at the
> bottom of the screen? They are all japanese, with no brand markings.
>
> <http://www.epcos.com/web/generator/Web/Sections/Publications/PDF/SIOV...>;=
> is the Epcos MOV databook, with datasheets for Telecom applications.
> page 213 list the TELECOM MOV data.
>
> =A0 =A0Every line into that studio building had a long distance call devic=
e
> diverter in the line that had MOV across the phone line. Every one of
> them survived the direct hit to the building and STL tower. That's more
> than can be said of your ability to use reason, and learn new things.
>
> =A0 =A0You need to get your head out of 1920 and learn modern electronics.=
> The one thing we learned today is that you don't know any more about
> Telecom that you do lightning protection, or reading comprehension.
>
W_ denies MOVs are commonly used in typical electonics or modern
appliances too. He had to, because he can't answer the obvious
question of how MOVs can be used effectively in these applications,
yet they can't work in plug-in protectors and the only way to get any
protection is to have a nearby direct earth ground. Faced with the
problem of MOVs providing protection in electronics/appliance without
an earthground, he simply denies MOVs are used in electronics and
appliances. Here's the references that I provvided him on that one:
Here, from Appliance Magazine and Appliance Design websites:
http://www.appliancedesign.com/CDA/Articles/Electronics/BNP_GUID_9-5-...
"New thermally enhanced MOVs help protect a wide variety of low-power
systems against damage caused by over-current, over-temperature and
over-voltage faults, including lightning strikes, electrostatic
discharge (ESD) surges, loss of neutral, incorrect input voltage and
power induction.
These devices help provide protection in a wide range of AC line
applications, including AC mains LED lighting systems, PLC network
adapters, cell-phone chargers, AC/DC power supplies (up to 30 VA as
input power for 230 VAC input voltage), modem power supplies, AC
panel
protection modules, AC power meters, and home appliances. "
http://www.appliancemagazine.com/print.php?article=3D1778&zone=3D1&first=3D1=
"Protecting increasingly sophisticated and complex control boards
from
misconnection, power surges, or short circuit damage is of particular
concern to the equipment manufacturer. Although appliance
transformers, their enclosures, and connections are capable of
withstanding higher voltage transients, the use of sensitive solid-
state devices on the board necessitates improved overcurrent,
overtemperature, and overvoltage control.
Coordinating overcurrent and overvoltage protection can also help
designers comply with safety agency requirements, minimize component
count, and improve equipment reliability. A metal oxide varistor
(MOV)
overvoltage protection device used in a coordinated circuit-
protection
strategy with a line-voltage-rated PPTC overcurrent device helps
manufacturers meet IEC 6100-4-5, the global standard for voltage and
current test conditions for equipment connected to ac mains."
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Author: Mike TomlinsonDate: 17:01 06-05-08
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Author: Mike TomlinsonDate: 17:04 06-05-08
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Author: Michael A. TerrellDate: 17:36 06-05-08
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nicksanspam@ece.villanova.edu wrote:
>
> Mike Tomlinson <mike@jasper.org.uk> wrote:
>
> >... This is an important principle of the UK wiring code. It's
> >referred to as "equipotential bonding."
>
> I wonder if "ring mains" (an extra wire from the last outlet to make
> a loop back to the fusebox) are legal in the US. Seems like a nice way
> to improve voltage regulation with a little extra wire, and if the ring
> wire only breaks in one place, all the outlets keep working.
No, the are not legal in the US.
--
http://improve-usenet.org/index.html
Use any search engine other than Google till they stop polluting USENET
with porn and junk commercial SPAM
If you have broadband, your ISP may have a NNTP news server included in
your account: http://www.usenettools.net/ISP.htm
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Mike Tomlinson <mike@jasper.org.uk> wrote:
>... This is an important principle of the UK wiring code. It's
>referred to as "equipotential bonding."
I wonder if "ring mains" (an extra wire from the last outlet to make
a loop back to the fusebox) are legal in the US. Seems like a nice way
to improve voltage regulation with a little extra wire, and if the ring
wire only breaks in one place, all the outlets keep working.
Nick
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Author: VWWallDate: 17:43 06-05-08
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|
trader4@optonline.net wrote:
> W_ denies MOVs are commonly used in typical electonics or modern
> appliances too. He had to, because he can't answer the obvious
> question of how MOVs can be used effectively in these applications,
> yet they can't work in plug-in protectors and the only way to get any
> protection is to have a nearby direct earth ground. Faced with the
> problem of MOVs providing protection in electronics/appliance without
> an earthground, he simply denies MOVs are used in electronics and
> appliances. Here's the references that I provvided him on that one:
>
> Here, from Appliance Magazine and Appliance Design websites:
>
> http://www.appliancedesign.com/CDA/Articles/Electronics/BNP_GUID_9-5-...
>
>
> "New thermally enhanced MOVs help protect a wide variety of low-power
> systems against damage caused by over-current, over-temperature and
> over-voltage faults, including lightning strikes, electrostatic
> discharge (ESD) surges, loss of neutral, incorrect input voltage and
> power induction.
I had a microwave oven that had a MOV across the 120V line ahead of the
power switch. The other side of the 120/240 20A circuit supplied a
refrigerator. The loss of the neutral applied a good part of the 240V
across the MOV when the refrigerator attempted to start.
The MOV didn't last long! It would probably have been OK on the load
side of the switch.
I know that refrigerators should be alone on a "home run" circuit, and
neutrals shouldn't be connected with wire nuts, but that wasn't how it was!
My only complaint with some plug-in protectors is that the MOVs are
often much too small. I've also seen some with only a line-line MOV.
--
Virg Wall, P.E.
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Author: Phil HowardDate: 20:12 06-05-08
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In alt.engineering.electrical nicksanspam@ece.villanova.edu wrote:
| Mike Tomlinson <mike@jasper.org.uk> wrote:
|
|>... This is an important principle of the UK wiring code. It's
|>referred to as "equipotential bonding."
|
| I wonder if "ring mains" (an extra wire from the last outlet to make
| a loop back to the fusebox) are legal in the US. Seems like a nice way
| to improve voltage regulation with a little extra wire, and if the ring
| wire only breaks in one place, all the outlets keep working.
It is not legal in the US. It is also considered technically unsafe.
You could wire a ring circuit with AWG #14 CU rated at 15 amps and protect
it with a 30 amp breaker under the theory that the current would be split
across the 2 paths between the source (breaker) and the load. This is the
most unsafe configuration because if one of the wires breaks, the breaker
will not detect it, and you won't notice until a fire starts.
You could wire the same circuit to two separate 15 amps breakers. In this
case it is somewhat safer because if one wire breaks, you can't get any use
via one of the breakers, effectivly reducing the current that would trip
the circuit via the remaining breaker. This is still unsafe because the
broken wire could merely be loose, and shutting off one breaker would leave
the circuit potentially live via the other breaker as the wire could come
back in contact.
There could also be confusion with separate breakers. The breakers have to
be on the same pole (phase), an issue not present in the single pole single
phase home wiring most homes have in UK. The USA, however, has two pole
single phase wiring. One way around that would be a "tandem" breaker with
the two handles fused together.
The safest case would be wiring both ends of the ring into the same breaker
rated for the current capacity of the wire as if used in a regular branch
circuit. Even this would have a safety issue. If the wire became loose at
one point in the ring, it would still be a potential hot spot that would be
not as easily noticed as a similar loose wire in a branch circuit. That hot
spot could then start a fire.
So far I have only described issues with the hot wiring. There are issues
with the neutral wiring as well. In all the above configurations, a neutral
would have to be wired in from both ends of the ring, and each be wired in
a separate hole (not doubled up) in the neutral bus bar. A loose neutral in
all these cases would go unnoticed just like a hot wire. But in cases where
the total current available (either the 30 amp single breaker, or tandem 15
amp breakers, described above) exceeds the wiring (when neutral is AWG #14 CU)
a wiring overheating problem exists.
The grounding wire would also have to be wired correctly from both ends.
An even greater double hazard potential exists when the neutral on one end is
broken while the hot on the other end is broken (or shut off at the breaker).
This creates a large inductive loop which can energize other wiring and cause
various problems with many metallic constructions.
Very little is gained by doing this over direct branch circuits. The issue
of voltage stability is addressed by keeping branch circuits short. It is
my understanding that UK ring circuits tend to be longer and run all around
the portion of a house (often an entire floor). Branch circuits in the USA
tend to be shorter.
Very long circuits can have voltage issues. An example is a home with a 1000
foot long driveway into the property, and a string of many lights along the
way. The more distant lights would be dimmer. This can be addressed to at
least balance out the dimming by using a loop-back circuit, which is still a
branch circuit. This is a more expensive circuit that is done by having an
extra hot wire run with the circuit in the same cable or conduit. Each lamp
is connected between the extra wire and the neutral. The extra wire is then
connected to the fed hot wire at the last lamp in the string. There is no
other connected to the fed hot wire other than the last lamp and the source
controlling switch. With this loop-back circuit, each lamp has the same
circuit length, and thus will have the same voltage drop.
The above technique was discussed on electrical-contrator.net a while back,
but they have since changed web site software, and my old links do not work.
--
|WARNING: Due to extreme spam, I no longer see any articles originating from |
| Google Groups. If you want your postings to be seen by more readers |
| you will need to find a different place to post on Usenet. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |
|
|
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|
Author: Phil HowardDate: 20:24 06-05-08
|
|
In alt.engineering.electrical VWWall <vwall@large.invalid> wrote:
| I had a microwave oven that had a MOV across the 120V line ahead of the
| power switch. The other side of the 120/240 20A circuit supplied a
| refrigerator. The loss of the neutral applied a good part of the 240V
| across the MOV when the refrigerator attempted to start.
|
| The MOV didn't last long! It would probably have been OK on the load
| side of the switch.
|
| I know that refrigerators should be alone on a "home run" circuit, and
| neutrals shouldn't be connected with wire nuts, but that wasn't how it was!
How would you connect a neutral? Doubled up on a receptacle device screw?
The usual practice is to wire the neutral in a wire nut so it can feed the
device in that box, as well as connect up and down stream, even if the
device is removed.
OTOH, I don't like wire nuts. I've seen them come loose even when wired
together well. Maybe it was a defective nut. I definitely will try to
avoid them when my new house gets built (a lot of bad electrical things
will be avoided in it).
| My only complaint with some plug-in protectors is that the MOVs are
| often much too small. I've also seen some with only a line-line MOV.
You had a plug-in protector for a double line (240V) circuit? Or are you just
referring to the neutral as one of the lines?
I'm still on the hunt for a plug-in surge suppressor power strip for 240V
with NEMA 6-15P plug and NEMA 6-15R outlets. The MOVs between each line
and ground need to be the ones appropriate for 120V (330V clamp rated) and
the ones between the two lines appropriate for 240V (660V clamp rated).
--
|WARNING: Due to extreme spam, I no longer see any articles originating from |
| Google Groups. If you want your postings to be seen by more readers |
| you will need to find a different place to post on Usenet. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |
|
|
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|
Author: Phil HowardDate: 20:27 06-05-08
|
|
In alt.engineering.electrical Eric <me@nomail.com> wrote:
| phil-news-nospam@ipal.net wrote:
|> In alt.engineering.electrical Eric <me@nomail.com> wrote:
|>
|> | I can attest to vhf/uhf content in lightning strikes. I worked for a
|> | communications outfit. We owned and maintained a number of comm sites
|> | with towers and antennas. One strike on an antenna destroyed the LDF rf
|> | cable all the way to the polyphaser at the bottom of the tower. It had
|> | blowouts at about 1 foot intervals all down it's length suggesting a
|> | 1/2 wave of about 1 foot or approx 460 mhz. That's one hell of a lot of
|> | energy at that frequency..
|>
|> Apparently you had some kind of resonance involved. Maybe the antenna itself
|> can cause that. Or the output tank circuit in the transmitter. Once you have
|> the resonance to narrowband the energy, it would only take a reflection back
|> up the line and you turn a propogating surge into standing waves.
|>
| Pretty much what we determined. Also in another thread I stressed that
| the rise time by itself does not determine frequency content. One needs
| to know the rate of change, or slew rate, to determine that. A
| lightning pulse may have a rise time of 1.2 microseconds but in that
| short time the current can rise to thousands of amps, generating a large
| amount of vhf,uhf energy.
In some plots of voltage rises I've seen in the past, the rise was not at all
a smooth one. It went up in steps. Of course if one _thinks_ there will be
no VHF or UHF energy and does measurement with a ssytem only capable of lower
frequencies, that would smooth out how the rise appears.
--
|WARNING: Due to extreme spam, I no longer see any articles originating from |
| Google Groups. If you want your postings to be seen by more readers |
| you will need to find a different place to post on Usenet. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |
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