Re: Zapping Camera Problem

["ABLE1" <nospamhere@xxxxxxxxxxx>]

"Robert Macy" <robert.a.macy@xxxxxxxxx> wrote in message
news:08dcd704-a1fd-4548-8bdb-e9ddd9d28dd0@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On May 23, 2:56 pm, "ABLE1" <nospamh...@xxxxxxxxxxx> wrote:
>..plethora of chloroform in print deleted...
> Robert,
>
> I don't mind learning something new, do it every day. I have always be
> fascinated with lightning as to its effects and potential. However not to
> the point of wanting to write a thesis on the topic. More importantly here
> is I want to find out what is needed to correct this problem at this
> location that seems to be most unique.
>
> Thanks for the technical theory link. I will read some of it someday.
>
> I get the idea that the grounds are the problem and that some additional
> connections need to happen to some additional devices. Already have done
> enough experimenting but have had no success with a cure. I have also
> determined that not every fix works in every application.
>
> The challenge is what device and where to apply.
>
> Thanks,
>
> Les

You have reasonable intelligence, right? If the 'expert' can't explain
it to you, THEY DON'T KNOW IT very well!

Translating all that theory into 'practical' ...Remember lightning is
HIGH FREQUENCY! We're talking over 100MHz with most of the energy
centered in the 1? 3? or sometimes 10 MHz range. Your AM Radio
stations are in the 1MHz range.

Next lightning is HIGH VOLTAGE [as if you didn't notice] but it also
has a lot of backup so it will supply oodles of current if there is an
'arc over' [in the 10,000++ Amp range - and during that short circuit
discharge all the current pretty much flies through all at once,
remember your house runs nicely on a 200A breaker box with only
220Vac, so you catch the drift of just how much power is there]

To kind of envision what a lightning strike is like, picture the earth
as a giant rubber sheet that is all at ground potential lying flat.
Suddenly lightning strikes the ground, which is like reaching down and
pinching the rubber sheet in that spot and pulling it 'up' to very
high potential. See how you made a teepee? Well that slope represents
the voltage gradients from the strike down to where the voltage is
again zero.

Now if the strike is energetic enough the difference in voltage
between two points, even if they're close together, can be
substantial. That's why four legged animals don't survive as well as
two legged animals with feet together huddled into a ball. New
thinking is don't lie flat.

Now back to your cameras. With a strike, or even a slight sizzler, one
building ground is at one potential and 200 feet away the other
building ground is at another, notice BIG voltage difference. But
wait, you've got a great conductor, camera cabling, tieing between the
two buildings! Just imagine what those cameras feel like with, say,
ground on the coax cable and their power supply leads are 10,000 volts
higher.  Big ouch, or at least potential for a big ouch.

How to fix?  This gets a bit tricky. The best way to fix the problem
is to filter out all that bad stuff.  Think how multi-stage filters
stop a signal. First you have a short to ground, then in series a high
impedance, and then another low impedance to ground, and so on. So you
have good ground at building A and another good ground at building B,
but you do NOT have a high impedance between the buildings! How to do
that? Buy tons of clamp on ferrites. Clamp along the cabling
connecting the two buildings. Make certain [if possible] to clamp
about every foot along the cable bundle and include ALL the cables as
you clamp each ferrite on.  There is probably good bypassing
[capacitance between +/- input and the coax itself is good. Don't know
about what power to coax is like. But you may not have to add anything
there.

So now here's how your 'protection' works. building A and building B
are NOT at the same potentential, BUT! because of all those ferrite
clamps as you go along the bundle of cabling the voltage variation
pretty much makes a nice uniform transition from A to B WITH the
relative voltages staying pretty close to each other. Thus, nothing
zaps the camera, because your structure can't create 10,000 volt
difference between power and coax.  Maybe only a couple hundred volts.

Sadly, ferrite clamps start becoming an impedance as you go up in
frequency, like at 50-100MHz, so one has to increase that impedance by
'looping' the cabling around at least once, more than three times kind
of gets counter productive. But the problem with looping is that it
provides a path bypassing the ferrite core just where the cable turns
on itself and gets close [remember the 100MHz energy?] this provides
an arc path. so some people use giant torroids to loop the cable
around for the low frequency energy and right near that point they
clamp a ferrite, making the protection a bit more 'broadband'.


I know this is simplistic, but a place to start.  You're not losing a
camera EVERY time, so perhaps this small amount of 'fix' will
suffice.
=====================================================

LOL  Buying tons of clamp on ferrites is not in the future.

At this point re-evaluating the current grounding should be the first step.
Need to get there before the next storm goes through.  Oh, to late, that
just happened earlier this evening.

Les