On Tue, 11 Mar 2008 11:52:17 -0600 bud-- wrote: | snipped-for-privacy@ipal.net wrote: |> On Mon, 10 Mar 2008 11:18:22 -0600 bud-- wrote: |> |> | For #2 w_ wants signal entry protectors connected directly to the |> | grounding electrodes instead of short connection to the earthing wire at |> | the power service. That may compromise keeping the ground references at |> | the same potential. 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." |> | Both guides emphasize a major source of damage is high voltage between |> | ground references, and that short interconnect is very important. (Else, |> | the IEEE guide says if there is not a short interconnect wire "the only |> | effective way of protecting the equipment is to use a multiport |> | protector.") If you have a relatively modest 1000A surge to earth and a |> | very good 10 ohms system-to-earth impedance the ground reference will |> | rise 10,000V above ?absolute? earth potential. All ground references |> | must rise together. I wrote about this in several posts earlier in the |> | thread. |> |> For low frequency surge energy, keeping things at the same potential |> is more critical, and that strongly suggests a short "intergrounding". |> |> For high frequency surge energy, the short interconnect can let such |> energy across from one wiring to another. High frequency surge energy |> can then cause damage to sensitive electronics as a result. | . | Both guides emphasize short interconnection. None of the six EEs what | wrote the 2 guides indicates a problem. But they all probably had a | hidden agenda like Martzloff.
You need to divert the high frequency energy to somewhere. If the only path to ground is via the interconnect, then it has to be short. If the energy were ONLY LOW frequency, then each system taking its own conductor to the grounding electrodes would be sufficient, as long as the conductors are sufficiently large to avoid a big voltage drop.
But high frequency energy is a reality, even if people like Martzloff are trying to deny it. Maybe his agenda is to avoid having to give a very complex description of _why_ to do as he suggests (afterall, the general public doesn't understand things like frequency of wave energy).
The short interconnection is the way to go, because the other choices do not have any easy way to mitigate their issues. At least with a short interconnection, you can still prevent high frequency energy from going to the appliance devices by having appropriate inductance in the path, or adding supplemental capacitive grounding, or both.
| The EEs at the IEEE that peer reviewed the IEEE guide didn?t see a | problem. They probably had a hidden agenda too. | | 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.
Summary: all wiring has transmission line characteristics of some form
| You have posted no link to a source that agrees with you. There is no | common science on which to base further conversation.
Then I guess PHYSICS is not one of your common sciences.
| None of the 6 EEs that wrote the 2 guides agree with you. (But they all | had a hidden agenda.) The specific example of suppression with a plug-in | suppressor in the IEEE guide (which you probably haven?t read) was for a | common mode surge. You have no links that agree with you.
Where do you think the energy of a common mode surge goes, when it proceeds down a branch circuit (whether that is a branch of power, telephone, or TV coax), and reaches a point of use surge protector?
If it is telephone or coax, and the protector is connected to a power circuit where it sink the energy, then that is certainly a direction the energy can go. But if the common mode surge is arriving on the power circuit, where would it go from there? When you send it over the telephone or coax wiring?
The best you can hope for on a common mode power circuit surge is to send it backwards the way it came in. To do that you MUST have something that will appear to be a high impedance to the surge, while not being so to the power you want to pass through to the protected device. Or better yet, don't allow the high frequency to propogate to the branch circuits in the first place.