Re: Long cat5 run question

DTC wrote:
I think ya'll aren't on the same page here, compounded by taking
quotes and references out of context.
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Where have I taken any reference out of context?
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There are two kinds of protection. The exact description may vary,
but its still a function of clamping the over voltage and shunting
the over voltage to ground, may it be done in a single device or with
two separate devices.

A MOS "surge protector" found in an outlet strip merely clamps
(or blocks) excessive voltage up to the point where the MOS device
fails. It offers virtually no lightning protection, per se.
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Almost all service panel suppressors and plug-in suppressors use MOVs - metal oxide varistors - for the power wires. MOVs clamp the voltage across them. Few plug-in suppressors work by blocking. I assume we are not talking about a direct lightning strike to a building which requires lightning rods for protection. Lightning then is almost always a surge coming in on power or signal wires. (The IEEE guide also discusses entry by difference in ground potential as at a pad mounted air conditioning compressor/condenser where the unit pad/’ground’ is shifted away from the power and control wiring.)

Francois Martzloff was the surge guru at the NIST and wrote the NIST guide. He also has many published technical papers on surges. One of them looks at a branch circuit with a spark gap at the source and a MOV at the end of the circuit. The spark gap represents a service panel which will arc-over from hot to ‘ground’ at about 6,000V [US]. It is a real good idea to have a service panel surge suppressor, but if one is not installed much of the energy of a large surge is dumped to ground by arc-over at the panel. Receptacles will also arc-over at about 6,000V [US].

The paper looks at the dissipation in a MOV at the end of a branch circuit. Because a surge is a very short event it is, in effect, high frequency. The inductance of the branch circuit then is much more important that the resistance. The high impedance of a branch circuit means not much of the surge can reach a plug-in suppressor. The maximum energy dissipated in the plug-in suppressor was 35 Joules. In 13 of 15 cases it was 1 Joule or less. That was with surges from 2,000 to 10,000A. (A strong lightning strike to the utility pole behind your house might produce 10,000A to the house from another Martzloff paper.) I recently bought a plug-in surge suppressor that had ratings of 30,000A and 590J per MOV for each of the 3 MOVs - H-N, H-G, N-G.

The single event rating of one of my MOVs is 590J. If the energy hits were smaller, 59J, the cumulative energy rating is far larger than 590J. With high ratings it is likely that a plug–in suppressor will never fail. (Service panel and plug-in suppressors do not protect by absorbing energy, but absorb energy in the process of protecting.)

In a different guide Martzloff wrote "In fact, the major cause of TVSS [surge suppressor] failures is a temporary overvoltage, rather than an unusually large surge."

All the technical papers I have read indicate plug-in suppressors can protect against even lightning strikes unless they are *very* near. With service panel suppressors, recommended, the protection is better.
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A gas tube (or old style carbon block) arrestor shunts the over
voltage to ground. Its very robust, but if the voltage is not high
enough to arc over the arrestor (as in the leading edge of the spike),
then the "surge protector" will block it.
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I don’t understand “the ‘surge protector’ will block it”.
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Either device if used by itself is not entirely effective.

bud-- wrote:
> w_ refers to plug-in surge suppressors as a ‘magic box’ because he
> can’t figure out how they work.

That was taken completely out of context.
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“But when one assumed the protector is some kind of 'magic box' protection, then damage becomes acceptable.” Reference is to plug-in suppressors. w_ can’t figure out how they work.
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w_tom wrote:
> Bud must post anything to avoid what is standard and fundamental to
> surge protection. A protector is only as effective as its earth
> ground. Earth ground - not a protector - provides protection.

Also taken out of context as Bud did indeed say proper earth grounding
was important.
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In fact I recommend reading the IEEE guide. For best protection the guide recommends:
- “single point ground” where entry protectors for phone, cable, ethernet, .... have their ‘ground’ connected with a *short* wire to the earthing conductor at the power service
- power service surge suppressor
- plug–in suppressors (used on high value equipment, particularly that connected to both power and signal wires, like a computer connected to power and phone)

My discussion is slanted toward plug-in suppressors because of w_’s misinformation on the subject.
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bud-- wrote:
> w_ has a religious belief (immune from challenge) that surge
> protection must use earthing. Thus in his view plug-in suppressors
> (which are not well earthed) can not possibly work.

LITERALLY taken, an in-line "surge protector" won't need a direct
ground to block a transient spike, so earthing doesn't come into
the picture. Look at a MOS device, there are two wires attached to it,
neither one goes to ground, its KIND OF like the reverse of a Zener
diode that doesn't conduct until a threshold voltage is reached. Look
at a gas tube protector, it has three wires - where the "third" wire
is the grounded shell of the device.

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Plug-in suppressors in the US (and probably about everywhere else) have MOVs from H-N, H-G, N-G. In addition, all signal wires to protected equipment needs to run through the plug-in suppressor. The suppressor works by clamping the voltage on all wires to the common ground at the suppressor. Because the ‘ground’ wire is relatively high impedance, they do not work primarily by earthing the surge. (Described in detail in the IEEE guide starting pdf page 40.)

Everything written above is based on the guides or Martzloff sources. The Martzloff references are probably still online if you want to read for yourself - I could find the links.

--
bud--
.

Relevant Pages

  • Re: Surge Protector for Friederich 24k btu Wall A/C Unit - Is it okay to use?
    ... That surge could not be stopped by three miles of sky. ... Grounding Sensitive Electronic Equipment"), an IEEE standard, recognizes plug-in suppressors as an effective protection device. ...
    (alt.home.repair)
  • Re: Soon to arrive my HDTV
    ... Why re-engineeer protection that is already inside every TV? ... a surge that seeks earth ground. ... That surge enters a TV to find earth ground outgoing via some ... destructive surge is on one or both AC wires and seeking earth ground. ...
    (alt.tv.tech.hdtv)
  • Re: Soon to arrive my HDTV
    ... Why re-engineeer protection that is already inside every TV? ... a surge that seeks earth ground. ... That surge enters a TV to find earth ground outgoing via some ... destructive surge is on one or both AC wires and seeking earth ground. ...
    (alt.tv.tech.hdtv)
  • Re: Lightning Strike and surge
    ... breaker box to what the electrician called "positive" lightning. ... the wires acting as a long wire or loop antenna. ... Of course w__ has still not figured out how plug-in suppressors work. ... - Why do the only 2 examples of protection in the IEEE guide use plug-in ...
    (alt.comp.hardware.pc-homebuilt)
  • Re: Lightning Strike and surge
    ... I wouldn't bet that an electrician could tell the difference. ... An example of a loop is a cable wire and power wires, with the wires connected at the ground bond, and the open end of the loop at a TV. ... Protection is for the power and phone and cable ground references to rise together. ... Plug-in suppressors work by clamping the voltage on all wires to the common ground at the suppressor. ...
    (alt.comp.hardware.pc-homebuilt)