DTC wrote:
> I think ya'll aren't on the same page here, compounded by taking
> quotes and references out of context.
..
Where have I taken any reference out of context?
..
>
> 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.
..
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.
..
>
> 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.
..
I don’t understand “the ‘surge protector’ will block it”.
..
>
> 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.
..
“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.
..
>
> 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.
..
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.
..
>
> 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.
>
..
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--