| firstname.lastname@example.org wrote:
|> |> | w_tom wrote:
|> |> |> So where does that plug-in protector dissipate surge energy
|> |> |> harmlessly in earth? It does not.
|> |> | .
|> |> | If not hindered by religious blinders w_ could read the answer in the
|> |> | IEEE guide (starting pdf page 40). 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. Plug-in suppressors do not work
|> |> | primarily by earthing (or stopping or absorbing). The guide explains
|> |> | earthing occurs elsewhere.
|> |> Clamping does not make surge energy disappear.
|> | .
|> | Clamping makes the voltage between wires going to the protected
|> | equipment safe for the protected equipment.
|> See what I said later in that post you are replying to. Sure, it does
|> equalize the difference for the most part. Other aspects of the surge
|> are not affected, or are affected in only minimal ways. For example
|> the surge front waveform is reduced because some of the energy can go
|> across the clamp and take another path away from the appliance. But
|> this is only reducing the energy to some fraction that can still be
|> enough to cause damage.
| You use transmission line characteristics. Using Martzloff?s statement
| of travel time on the circuit, the circuit is a fraction of an inch to a
| MOV and about 6 feet to the protected equipment. Transmission line
| characteristics would require on the order of a 10 nanosec surge. A MOV
| will effectively clamp the voltage to a safe level.
I'm not concerned with the distance to, or across, an MOV. You still seem
to be missing my statement where I acknowledge the MOV tend to equalize
the voltage between the wires. A surge waveform is relevant, and may even
be relevant to the MOV connection, but I have not yet even needed to address
that (and have not done so).
Consider that the MOV is equivalent to the two conductors being shorted
together, without considering the effect of that short on the service the
wires are intended to provide (since in reality the MOV is supposed to
become such a short for the duration of a surge above a certain voltage).
The wires are shorted at zero distance. Let's not even worry about the
change in characteristic impedance as the wires approach each other (as
this doesn't contribute much effect, anyway).
Two wires shorted somewhere within the run is actually 4 total wires
meeting at one point. A surge arriving at such a junction will have
to see an impedance change merely because there are many paths to go.
The only exception would be where the characteristic impedance of ONE
wire is 1/3 of what the other three in parallel are. And that is a
case that won't happen when you are dealing with TWO of them arriving
together as a transmission line pair. What this means is that the
surge arriving at the junction will go back out on all FOUR wires, not
just the other three.
Given a differential surge coming in on two wires, that is the same as
two surges of opposite polarity. Both go out all four wires. But over
the two wires the surge did not come from (e.g. the two that go on to
the protected appliance), these two opposite polarity surges will go
in about equal amounts. So they have the effect of (mostly) cancelling
out. In addition to that, both wires going to the appliance will have
any latent surge now in common mode rather than differential mode.
The common mode surge is more subject to external inductance. So you
could, for example, wrap the power cord (both wires in parallel) to the
appliance in a loop around a toroid and reduce the very high frequency
components that might still be there even more.
Given a common mode surge is different. The MOV is going to have little
or no effect since there is little or no voltage across it. Fortunately
as described above, the common mode surge is more easily blocked with
inductance on a "whole cord" bases (both current carrying conductors in
parallel through the inductive winding). The branch circuit length itself
will be significant, too.
Surges don't all come from the same place. They can also be induced on
any circuit directly from a nearby strike. The common mode aspect of a
pair of wires that makes it inductive enough to reduce the high frequency
components of a surge is also its disadvantage to an induced surge. You
can end up with these high frequencies, anyway. So it is better to have
line inductance added with your plug-in surge protection close to the
appliance to be protected. My plug-in surge suppressors include some.
I'm looking at adding substantially more at some point.
| And provide a source that agrees with you that transmission line
| characteristics apply.
Why don't you just actually discuss the technical details yourself
instead of trying to "involve" someone who is actually not a part of
the discssion. Or is this beyond your level of understanding to do?
|> |> The proportions depend on the characteristic
|> |> impedance, as that is the only impedance that has an immediate effect with
|> |> reflection time frame short enough to not need to be considered.
|> | .
|> | Francois Martzloff was the NIST guru on surges. He did research and has
|> | many published papers on surges and surge suppression.
|> | On transmission line behavior Martzloff writes:
|> | "From this first test, we can draw the conclusion (predictable, but too
|> | often not recognized in qualitative discussions of reflections in wiring
|> | systems) that it is not appropriate to apply classical transmission line
|> | concepts to wiring systems if the front of the wave is not shorter than
|> | the travel time of the impulse. For a 1.2/50 us impulse, this means that
|> | the line must be at least 200 m long before one can think in terms of
|> | classical transmission line behavior."
|> You've quoted this before. In all cases I can remember, you quoted it
|> inapplicably. The evidence of your error exists right there in the words
|> you quoted. The part that says "if ..." is a conditional. It means that
|> the statement being made only applies under certain circumstances. Yet
|> you (who don't seem to understand this) quote this even where it does not
|> apply (e.g. in cases where the if-clause is not met).
| Martzloff?s 1.2/50 us waveform is a standard IEEE surge waveform. It is
| a standard waveform because it is characteristic of waveforms of surges
| produced by lightning. Martzloff, an expert in the field, used an
| appropriate and representative waveform.
Not all lightning strikes are alike. There is a *HUGE*
span of differences
in specific strikes. A "standard waveform" has uses in making comparisons
between different protective devices within the characteristics of those
waveforms. But no _one_
waveform is going to even come close to describing
the range of possibilities of individual lightning strikes _and_
proximities to such strikes.
| One of w_'s favorite professional engineer sources says an 8 microsecond
| rise time for a surge produced by lightning is a "representative pulse",
| with most of the spectrum under 100kHz.
I don't care what w_tom says. I don't consider him to be any more of an
expert than you.
| You claim surges resulting from lightning have rise times about a
| thousand times faster than accepted IEEE standards - which are
| experimentally derived.
Again, you have some reading comprehension problems. I do not say that all
surges have the same rise times. Instead, I say there is a wide variety.
The lightning itself has a wide variety, but can easily have rise times
well over 10A/ns. Leader strikes and even the first stroke typically have
much less. But secondary strokes can have a lot more depending on the
timing and the associated channel field. Just how much voltage you get
from that current depends on many factors, including proximity, and the
possibility of direct contact with the lightning current.
A standard waveform might might provide a good means to study and research
various devices, and compare them. But it does not model reality of nature.
I have seen lightning strikes hit small wires and do nothing to them, and I
have seen lightning strikes that have blown a detached garage to pieces.
I've seen the results of strikes that merely leave a dead radio front end
transistor, and strikes that vaporized the transmission line and left a
fraction of the radio present.
| Provide a source that agrees with you.
I'm here ONLY to discuss the issue, not to proxy the discussion to others
that are not participating.
Why don't YOU invite Martzloff to join in on the thread?
|> | I have posted this at least twice previously in response to your
|> | comments on transmission line behavior. Your response was that Martzloff
|> | "flubbed the experiment". You have never provided a supporting source
|> | for you belief.
|> The "supporting source" is the very statement you quote. Again, it is a
|> conditional statement that depends on a specific kind of impulse/waverform
| Waveforms that are well accepted as characteristic real world surges by
| people that are competent in the field.
One waveform is not the real world. Anyone who thinks one waveform models
the vast variety of lightning is a fool. I'm sure Martzloff is not doing
that. It must be you that is misreading the paper it misapplying what is
|> His "flubbed" experiment was not one to characterize all surges. I say
|> it was "flubbed" because it did not meet the needs YOU are trying to apply
|> it to (which seems to be the assumption that all surges are alike).
| If Martzloff was as stupid as you think he is his papers would not be
Or maybe the "flubb" is that he wasn't actually doing the experiment you
think he was doing. Maybe he was doing a standardized waveform test, and
not one with real lightning.
| Provide a source that surges produced by lightning are far faster than
| the 1.2/50 us Martzloff used.
Experience in the field.
And you really need to try to understand that I am NOT, and never have,
said that every lightning strike is faster. I am saying, and always have
said, that _some_
strike-to-surge situations are. There is a wide range
of lightning strikes and a very wide range of proximities involved.
|> | Provide a source that agrees with you that transmission line effects
|> | have to be considered for surges in other than large buildings.
|> I don't intend to do that. I don't need to.
| In other words you can?t. You prefer phils phantasy physics.
This is a technical discussion, not a paper-show-off forum. What I note
is that you never have, and I highly suspect never will, find any way to
actually discuss the technical aspects of this YOURSELF.
|> This is a guide for people who are only going to be doing minimal levels
|> of protection. A minimal level happens to be adequate for most people.
|> This guide does not cover the extensive protection needed that balances
|> between special requirements and the rare and very destructive extreme
| Not hardly for minimal levels. It is consistent with standards for
| surges conducted in on utility wires. The standards are based on a
| 100,000A lightning strike (very strong) to a utility pole behind your
| house, a near worst case. If you combine the 4 methods above using
| suppressors with high ratings and connect plug-in suppressors correctly
| you are very unlikely to have a loss.
Sorry, but that is not a worst case scenario. But even that scenario
can, depending on many factors, result in a vaporized plug-in suppressor.
I have had at least 3 direct strike events myself.
| Connected correctly all interconnected equipment is connected to the
| same plug-in suppressor and external wires, like cable, go through the
Parroting the proper way to connect the equipment wins you no points.
It's helpful to people that don't know. But you aren't making any kind
of technical discussion out of this.
| Still excluded are direct strikes to a building which require lightning
| rods for protection.
That is ONE form of protection. It is not an alternative form. The best
protection involves the maximum set of protection methods deployed in a
non-conflicting way. But you have to understand how the surges come in
and transmit to be sure you haven't combined protections in way that ends
up making things worse.
|> | My comments in response to w_ are disproportionately about plug-in
|> | suppressors because of the nonsense w_ posts about them.
|> Maybe you should just disregard him entirely.
| Maybe you should disregard the discussion aimed at w_.
I respond to obvious errors, including errors of omission where readers
may misunderstand something due to the omission.
|> | For surges coming in on utility wires, the impedance of the branch
|> | circuit greatly limits the current, and thus energy, that can reach a
|> | plug-in suppressor. Investigations by Martzloff with surges up to
|> | 10,000A at a power service (the maximum reasonable surge) and branch
|> | circuits 30 ft and longer with a MOV at the end, showed surprisingly
|> | small energy absorption at the MOV. The maximum energy dissipated in the
|> | MOV was 35 Joules. In 13 of 15 cases it was 1 Joule or less. One reason
|> | is the branch circuit impedance. The other is that at about 6,000V (US)
|> | there is arc?over from service panel busbars to
|> | enclosure/ground/neutral/earth. After the arc is established the arc
|> | voltage is hundreds of volts. That dumps most of the surge energy to
|> | earth. Receptacles (US) will also arc-over at about 6,000V.
|> First of all, an MOV is not going to absorb much energy. It is a device
|> that creates a low impedance path between two conductors. The energy it
|> absorbs is the current, times the voltage DROP, integrated over time.
| A MOV in a service panel suppressor absorbs a lot more energy than a
| plug-in suppressor because it is not isolated by the impedance of a
| branch circuit and is not protected by arc?over at the panel (it clamps
| the voltage far below arc-over). As I wrote, MOVs absorb energy in the
| process of protecting (energy absorbed as in your post). They don?t
| protect by absorbing the energy in the surge.
The energy absorbed by an MOV would be the voltage drop across the device,
times the current through the device, integrated over time. In its non-
conductive state, the current through an MOV is virtually zero. In its
conductive state, the voltage drop across an MOV is virtually zero. If
the MOV absorbed any substantial energy, it would be vaporized. The MOV
is a current diversion device. Where it diverts a surge wavefront to
some other path where it can do no harm, that is good. Where it diverts
a surge wavefront to merge with its opposite polarity counterpart (in
the case of a differential surge), that is good.
|> What is of more concern is where the rest of the energy went. It goes
|> out in all directions in response to impedance characteristics.
| You have provided no source that agrees with you that transmission line
| characteristics are relevant.
| And Martzloff contradicts you.
I have seen no post here, nor any paper, where he has specifically said that
anything I say is wrong. Basically, he hasn't addressed anything I say. You
are the one that is _interpreting_
Martzloff's writings as being in conflict
with my posts. Yet you have not correctly pointed to any relevant difference.
|> |> | 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.
|> |> Why is it that you always seem to want a binary answer about whether a
|> |> surge protection device is or is not effective? The true and correct
|> |> answer will be "it depends".
|> | .
|> | w_ says never. What I have read from many Martzloff papers and other
|> | sources is that plug-in suppressors with high ratings connected properly
|> | are very unlikely to fail. That is why some plug-in suppressors can have
|> | connected equipment warrantees.
|> The existance of a warrantee does not ensure protection. Surges do not
|> give a damn about the warrantee. If they did, they'd probably make more
|> of an effort to destroy everything just to spite the owner of the devices.
| The existence of a warrantee indicates the manufacturer doesn?t think
| the device will fail. Manufacturers for some devices have a lot more
| confidence in the devices than you do.
You also have a lack of understanding of business and product marketing.
that these devices can and do fail. Some don't care.
Some do care, and will cover the losses because part of what they are selling
is the peace of mind. They are not selling absolute protection. But they
can (and many do) sell protection that is adequate for most people.
|> |> | Never answered - embarrassing questions:
|> |> | - Why do the only 2 examples of protection in the IEEE guide use plug-in
|> |> | suppressors?
|> |> Because the IEEE guide you looked at is a guide about how to use plug-in
|> |> suppressors to their greatest effectiveness.
|> | .
|> | Your comment is beyond stupid. Perhaps if you read the guide....
|> Perhaps if you applied the guide correctly.
| The IEEE guide is much broader than plug-in suppressors, which is what
| your post said.
It has been misread by bud.
|> I read it a long time ago. It didn't cover all aspects of protection. Since
|> it was intended for specific readers, it doesn't even need to cover all
| The "specific readers" the guide was aimed at are "electricians,
| architects, technicians, and electrical engineers".
... who are deploying typical or average protection systems.
|> |> | ? Why don?t airplanes drag an earthing chain?
|> |> That would make it too easy for terrorists to grab hold of and yank the
|> |> down.
|> |> Silly question, silly answer.
|> | .
|> | It is a serious question. w_ says you can?t protect without the
|> | protector directly earthing the surge. Then it is not possible to
|> | protect airplanes.
|> It seems you have a broad lack of understanding, despite reading all these
|> various guides.
| It seems you have a broad lack of understanding of logic.
Point out some specifics if you think so.
| Start with a statement often repeated by w_ "no earth ground means no
| effective protection."
I do not support that statement. But I do stand by the statement that a
plug-in suppressor used exclusively cannot provide 100% protection. I do
say that the maximum level of protection you can get will involve an earth
ground as the least harmful place to divert the bulk of the surge energy.
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