On Thu, 13 Mar 2008 14:17:08 -0600 bud-- wrote: | snipped-for-privacy@ipal.net wrote: |> On Wed, 12 Mar 2008 10:42:51 -0600 bud-- wrote: |> | snipped-for-privacy@ipal.net wrote: |> |> On Tue, 11 Mar 2008 11:52:17 -0600 bud-- wrote: |> | . |> |> | Martzloff specifically looked at whether branch circuits exhibited |> |> | transmission line characteristics. They don't, as I previously posted |> |> | (ignored of course). But we all know Martzloff had a hidden agenda. |> |> |> |> If you believe Martzloff (re: branch circuits do not have transmission |> |> line characteristics) then I challenge you and him both to explain how, |> |> in terms of PHYSICS, that this can be so. I have used NM 14/2 cable as |> |> a TV feedline before. It works. It works as well as twin line. It is |> |> stupid to waste such expensive cable when mere twin line is sufficient. |> |> It was a temporary measure at the time because I was out of twin line. |> | . |> | It should have been obvious from the context that Martazloff was |> | investigating if branch circuits exhibit transmission line |> | characteristics *for surges*. They don't. (But Martzloff had a hidden |> | agenda.) |> |> Then he flubbed the experiment. Is *HE* willing to disclose how he did |> the experiment? I can't be specific in challenging his errors if I do |> not know what it is he did. I can only challenge him in general. | . | One source (not the only one) is: |
formatting link
| This is a technical paper published by the IEEE.
He dismisses "short pulses" without an explanation of why. Maybe it could be that agenda thing?
He doesn't even address fast rise edge transitions.
| 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."
He is already assuming a slow rise impulse. This isn't applicable to the points I raised.
| Houses don't have 200 meter branch circuits. In addition, the 1.2us rise | time Martzloff used is not likely. The source impedance of wiring from | the point-of-strike to a house attenuates the highest frequency | components and gives a slower rise. The typical test surge, IIRC, is | 8/20. That would require a much longer branch circuit.
"Houses don't have 200 meter branch circuits" ... certainly no _normal_ house would have anything close to that. OTOH, if they did, they would not have so much of an issue with surges as that long wiring would work in favor of attenuating the short rise pulses and edges that Martzloff so conveniently dismisses.
| ---------------------------- | Martzloff also writes: | "Will the impinging surge be in the normal mode (black to white) or in | the common mode ([black-and-white-to-green)?" | This is not your definition of a common mode surge (but it is my | definition).
Definitions of modes is, in part, a word game. There are many modes that can actually happen. They can all be described in terms of a combination of differential and common mode. The term "normal" might be a custom in this field of engineering, but it is a term within inherint meaning.
| Martzloff shows using 1-3 MOVs at the end of a branch circuit for surge | suppression. He indicates none of the problems you say exist.
Because in the remainder of this paper he isn't addressing them. He is addressing the slow rise impulses up to make a few hundred kHz equivalent frequency.
| None of the 6 experienced EEs who wrote the guides agrees with you. (But | they all probably had a hidden agenda.)
Either the hidden agenda, or maybe just a lack of interest in their part to explore the field of fast rise time pulses and edge transitions.
| Where are your sources???
Where are YOURS? You "came to a gun fight with a knife". Your evidence doesn't even deal with fast rise time issues.
|> My sources for physics are college classes I have taken, as well as other |> readings in the past. Physics is one of my areas of understanding. | . | Apparently no degree in EE but you can accuse a respected electrical | engineer, who has many published papers on surges and protection, of | having a hidden agenda.
You seem to be a good source of his papers. Maybe you've read many others. If so, maybe you would do better than I at finding what he has written on fast rise time issues (as opposed to the paper you offered that did not).
Or maybe he hasn't written any. Maybe his "hidden agenda" is merely his interest in researching low rise time impulses (after all, they do happen more often then fast rise time impulses, which generally require a direct strike on the service drop).
FYI, I'm talking about rise times on the order of 1000 volts per NANOsecond or faster.
|> not know all areas of physics, but I do know transmission lines. | . | "If all you have is a hammer everything looks like a nail?"
Pounding a screw into wood might not be very efficient, but it can get the screw into the wood.
A fast rise impulse/edge might not propogate on NM as well as it would on TV twin-lead, but it can still have significant damaging energy at the far end. Remember, normal houses don't have 200 meter branch circuits.