When I wear my SCADA hat grounding takes a front seat. We take
great care to insure we follow sound methodology and take no short
cuts. I have shared many posts on how we do it... basically all of
it hinges of Franklin method. Those who know me, know I don't pull
punches...if we were getting hit allot I would post it. Yes we have
had hits and lost equipment but it is extremely rare. Consider that
one SCADA network alone has over 500 sites with elevated tanks,
towers and masts all with yagis, sectored and omni antennas with
heliax cabling. Wisps around here get more hits. I will share some
links you might find useful.
On Dec 29, 2015 8:08 PM, "Faisal Imtiaz" <fai...@snappytelecom.net
<mailto:fai...@snappytelecom.net>> wrote:
I thought about commenting, walked away, but decided to comment
at the risk of offending someone, but it would be worth it if the
point being made and the information being shared was understood
properly..
So here goes... Joshaven took the time and provided a farily
accurate, detailed post on how to do grounding properly, and the
potential issues when it is not proper. There is a lot of good
information in there.....
Glen I don't know if you realize what you did with your replies
.... while sounding dismissive you actually have described the
exact thing that Joshaven was trying to point out, as to what
happens when grounding is not proper !
'Grounding' is not just running some copper wires to be visually
satisfying.... your statement about 'it is grounded pretty
well...' followed by .. I have lost equipment there is an
Oxymoron....
Grounding when done correctly will protect your equipment from
having the type of damage you are describing.... and yes there
are some ways to measure and determine if your grounding is proper !
BTW, Audio affects of a Lightning strike, shaking stuff etc etc
is due to sound waves generated.. (sort of a mini explosion)...
makes for great sound effect, but has nothing to do with
electrical damage to equipment.
:)
Faisal Imtiaz
Snappy Internet & Telecom
7266 SW 48 Street
Miami, FL 33155
Tel: 305 663 5518 x 232 <tel:305%20663%205518%20x%20232>
Help-desk: (305)663-5518 <tel:%28305%29663-5518> Option 2 or
Email: supp...@snappytelecom.net
------------------------------------------------------------------------
*From: *"Glen Waldrop" <gwl...@cngwireless.net
<mailto:gwl...@cngwireless.net>>
*To: *af@afmug.com <mailto:af@afmug.com>
*Sent: *Tuesday, December 29, 2015 6:02:24 PM
*Subject: *Re: [AFMUG] WISP insurance
Forgot to mention, this was one hell of a storm.
Lightning from *several* miles away shook my home enough that
the dishes rattled, the TV moved, cabinet doors opened and
closed, etc, for upwards of 45 seconds.
I’m honestly surprised we only lost one tower in that storm.
I was preparing myself for putting up at least a couple of
replacement towers over my Christmas break instead of goofing
with the wife and kids. We got lucky and only lost some
electronics.
*From:* Glen Waldrop <mailto:gwl...@cngwireless.net>
*Sent:* Tuesday, December 29, 2015 4:57 PM
*To:* af@afmug.com <mailto:af@afmug.com>
*Subject:* Re: [AFMUG] WISP insurance
It is grounded pretty well, couple of ground rods, tower is
grounded and the copper goes to the top, tallest point for
quite a ways out there. The strike also blew out the
neighboring transformer (didn’t hit my equipment directly).
I have not been tying in my electrical ground with my tower
ground. I do believe I’m about to change that.
I do have a few other towers where the electrical ground is
tied into the tower ground which is also tied to a copper
wire (6 or 8, depending on what I had at the time) the entire
length of the tower, bolted to the tower at the top and bottom.
Those have also been struck.
One of my most recent ones ran up the ethernet cable, fried
the equipment at the top. POE on the ground survived, UPS
survived and the surge suppressor (10/100M fusible link
essentially) survived. The only radio to survive the strike
was the only one I had forgotten to install a suppressor on.
They were all replaced of course. The only equipment I’ve
seen survive an actual lightning strike without a hiccup is
the RB600. Everything else seems to die within 6 months.
It appears the surge went through the ground (which we’ve
gone over several times) into the surge suppressor, into the
ethernet and blew out the radios.
Any speculation on that would be awesome. The only thing that
makes sense is that maybe the static was close enough to hit
the electrical ground and go up the tower, but we’ve checked
the ground rods and copper, bolts, etc.
*From:* Joshaven Mailing Lists <mailto:lis...@joshaven.com>
*Sent:* Tuesday, December 29, 2015 1:18 PM
*To:* af@afmug.com
*Subject:* Re: [AFMUG] WISP insurance
Kinda off topic... Insurance of another type (avoidance)
I often find locations where the grounds are hooked up to the
tower ground which includes one or more ground rods… but what
often goes unrealized is that the system is also grounded to
another system through the utility company… and the tower and
the utility company may not be properly bonded. So the
lightning finds the big tower, and thinking it is a lightning
rod… uses some of the path to ground through rods at the base
of the tower but then also uses the path through the
equipment to get to the power utility ground…. and pop goes
the radio and router and such… Just don’t be that guy that
connects the big lightening rod to the utility power ground
through your router...
Your equipment should be surviving lightning strikes. Large
towers can be struck multiple times per month and equipment
can be on them for years without any damage at all. The fact
that you lost equipment says that the strike was either
direct to your equipment or you have a grounding issue that
made your equipment a better path to ground.
At some sites commercial radio engineers will even bring in a
beaded cable from the tower and spread it across the floor to
set all equipment on just to be sure that the ground panes
are entirely bonded. The reason that equipment blows is that
the difference in positive to negative current is out of
range. When you get a lightning strike and things are not
well bonded then you can have variances between grounds in
the order of thousands of volts which will make your
equipment pop like a fire cracker… if your ground is at
10,000v (relative to an average earth voltage) and your
equipment is at 10,024v then the potential between them is
24v. It is like a bird setting on a high voltage line…
somehow they don’t “feel” the high voltage… The trick to
surviving a lightning strike is to bond all grounds well so
ground is constant and then to have your power level
referenced from that ground. This way if the earth ground or
the tower ground or anything else has a sudden change then
your equipment changes with it and remains relatively the
same. After bonding your grounds properly so that you don’t
end up with thousands of volts difference between two grounds
like your power company ground and the tower that your
equipment is mounted to… then you can install good surge
equipment that will handle current overages in the event that
you need it.
The thing to keep in mind when grounding your equipment is
that you don’t want your equipment to experience a situation
like 0v for negative, 24v for positive and 50,000v for
ground. If your equipment ground plane floats with a strike
then it won’t even know that it experienced a surge. Just
like a boat going over shallower and deeper water — who knew
unless they had a fish finder running?
During a strike, you don’t want a 5,000v on the utility
ground while you have a 25,000v on the tower… If the cable
between the two (or patch of earth between rods) won’t handle
the surge or the impedance is too high then your equipment
will possibly have two grounds with two very different power
levels so the power will transfer from your shielded cable
through your router chassis to the utility power until a
something pops. The bottom line make the tower, earth, &
utility power all the same and properly ground your equipment
to that and you’ll survive most strikes perfectly fine.
if you want some good reading google the terms: “copper.org
<http://copper.org> lightning” they have some great
write-ups with pictures of the good, bad and ugly.
Sincerely,
Joshaven Potter
Google Hangouts: j...@g2wireless.co
Cell & SMS: 1-517-607-9370 <tel:1-517-607-9370>
supp...@joshaven.com <mailto:supp...@joshaven.com>
On Dec 27, 2015, at 10:31 PM, Craig House
<cr...@totalhighspeed.net> wrote:
2 in a year? We had 7 last night.
Sent from my iPhone
On Dec 27, 2015, at 21:22, Glen Waldrop
<gwl...@cngwireless.net> wrote:
We’ve had another lightning strike, at least the
second one this year.
I’ve got this feeling that our insurance company is
probably going to start to get a little difficult in
the near future.
Who do you guys recommend?
I’ve read about a few that cover everything, CPE,
tower equipment, towers, labor, etc... I imagine
those probably cost roughly what we bring in a year,
but...
Thanks guys.
