In alt.engineering.electrical w_tom wrote:

| Bud claims plug-in protectors provide a complete protection system -
| can protect from all types of surges. A plug-in protector only
| protects from surges that rarely damage appliances. As demonstrated
| repeatedly in other posts, plug-in protectors have even earthed a
| typically destructive type of surge through adjacent appliances. A
| problem alleviated by earthing a 'whole house' protector.

I don't agree with that assessment of the plug-in protector. If the
appliance has its own MOVs to protect stuff, then this would be true.
Not all do. Some appliances are more sensitive than others. It just
depends on what kind of surge is arriving, and where from. If it is
differential mode on the power wires, the plug-in protector can do
some important protection. Even with whole house protection in place,
you can have some energy get past it, and the surge can be induced into
the building wiring. Usually the induced surge is common mode, which
by itself is less of a problem. But if the appliance is connected to
more than one wiring, such as a computer with modem, then induced
surges can be more of a problem because of the difference between the
wiring. If the plug-in surge protector has them all attached at one
point, that should serve to equalize the voltage in most cases enough
to avoid damage.


| So that plug-in protectors do not compromise protection inside all
| appliances, the typically destructive surge must be earthed BEFORE
| entering a building. That solution is used everywhere professionals
| install protection. Everywhere. Bud also denies this.

The entrance protection, which works a lot better if earthed, is very
important for the big surges arriving on the service wiring. Being
earthed, it will sink most of the low frequency energy. That leaves
a partial surge that can still propogate beyond that point, as well as
induced surges which the entrance protection didn't even get a shot at.


| If a destructive type surge is properly earthed, then one can spend
| money on plug-in protectors to also protect from a typically non-
| destructive surge. This is called "complete protection". However
| better facilities make that whole house' protector even more effective
| by enhancing earth ground. Where is money better spent?

There is certainly a best "complete protection". I agreed that when
Bud focuses on one type of protection and calls it effective, he is
merely toying with the word "effective". It is better than nothing.
It can even reduce the number of damaging incidents a lot. But it is
not "complete effectiveness". But neither is "whole house" protection.

What one needs for the best is "everywhere protection".


| If not using a 'whole house' protector, well, even 'scary pictures'
| created by typically undersized protectors now creates a hazard.

There are tradeoffs. Bud is focusing on the low frequency energy and
seems to think that is all there us because a lot of documents focus
on it because more energy is in the low frequencies. Also, surges
that come from a greater distance have the higher frequencies reduced.


| Bud disputes this. Bud says if all wires connect to the same
| protector, then surge energy somehow disappears. Obviously not true.
| That surge energy must be dissipated harmlessly into earth. Just
| another reason why plug-in protectors create problems when a 'whole
| house' protector and (more important) proper earthing is not
| installed.

It depends. The surge consisting of primarly low frequency energy
(under 1 MHz) gets distributed around more evenly. The advantage is
that leaves less voltage differences between various wires. This is
an advantage to devices connected to more than one wire, like a TV
with cable. Without it, the surge arriving in common mode on power
(the plug-in suppressor won't stop that) will go through the TV and
on to the cable, generally zapping the tuner front end stage. But
if the cable is connected in parallel to the plug-in protector, then
the cable and power are at about the same voltage. The risk of damage
is much less that way. This applies to low frequency energy, which is
the more common. OTOH, if high frequency energy is coming in, such as
a direct strike on the mast of the power service drop, with shorter
branch circuit wires in the house, then the high frequency energy can
cross over from the power to the cable and zap the front end stage
just from the fast rising wavefront.

It's a give and take. Adding the plug-in surge protector connected to
all wires reduces certain surge effects, and increases others. The
advantage is gained when what you decrease is more common than what you
increase.

Bud either does not understand the high frequency energy or just does
not believe it can happen. All lightning strikes have it. It does
get attenuated quickly on wiring that has inductance. When the surge
is in common mode, as it will be in the wiring from most direct strikes,
the inductance on the wire is substantial, and the high frequencies will
be attenuated quickly. But, once _part_ of that energy is diverted to
ground on _one_ of the wires (e.g. the neutral that is grounded), then
_part_ of the surge is now differential (or transverse) mode, and that
part can propogate high frequency energy further on wire _pairs_.

One important way to protect against high frequency energy is to have
inductive blockage. That's practical to do on power lines. It can be
done on phone, but it has to be reduced if DSL is being used. There
are special DSL-specific telephone surge protectors that have low pass
filters to the service and high pass filters to ground with a cutoff
frequency above the DSL level. Othewise they can do the cutoff way
lower just above the voice level.


| Others claim a plug-in protector will stop or magically absorb
| surges. Obviously no protector stops lightning. Obviously (from so
| many professional citations) lightning damage is routinely eliminated
| by diverting typically destructive surges to earth ground "where it
| will do no harm".

Actually, it is possible to make an absorption-type protector. It is
not a trivial thing, and you would never want to do so inside a house.
I have built one. It consisted of a zig-zag phone wire running through
a large 8 inch PVC pipe filled with steel wool. At one end going to
the building, was a lot of inductance (the phone wire wrapped through
half a dozen large ferrite cores). The whole thing was buried in the
ground. It took a hit a few months later and was destroyed. The phone
wire was burned up. The steel wool was gone. The pipe was shattered.
The computer the phone line was connected to was undamaged.

Oh, it did have some diversion, as well. A pair of #12 copper wires was
run along inside the pipe, running into ground several feet on each end.
Those wires survived the event.


| Yes, plug-in protectors do have limited protective functions. But
| the discussion is about the type of surge that typically does surge
| damage ? that finds earth ground destructively through appliances.
| Any protector located too close to appliances and too far from single
| point ground cannot protect from that type of surge. So Bud invents
| this magic plug-in protector that somehow makes surge energy disappear
| and that, by itself, is a complete protection system.

There are lot of different types of surges that cause damage. There is no
one protection that can defeat them all.


| Bud pretends that typically destructive surges don?t seek earth
| ground. Even plug-in protectors need that properly earthed 'whole
| house' protector so that plug-in protectors do not contribute to
| adjacent appliance damage. Only then can a plug-in protector do what
| it is designed to do - protect from a type of surge that typically
| does not cause damage.

He is partially right. The common mode does "seek ground" in the sense that
the big difference is there. The differential mode is just propogating where
it can (and it can go further). Both can consist of low (more often, and more
energy) frequency and high frequency.

Connect two TVs to an antenna. Connect the chassis of ONE of them to ground.
The one with the ground connection will be more often damaged alone. But
there are also times when the other one can be damaged alone. Often both
will be damaged. It depends on things like whether the surge in the wire
is induced or direct. It depends on if you have additional lightning
arrestors on that wire (which can even change common mode to differential
mode and change which TV will be damaged).

The two of you are arguing entirely different aspects of surge issues that
has some degree of overlap. And it seems both of you have an incomplete
understanding of all the possible issues (or at least have only expressed
point regarding said subsets).

There is no simple answer to surge protection. There are some good practices.

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