one of the most classic examples of a 'split ground' situation is when
you loose gear with rain during hot days (first rains after dry
season). Because there is rain involved most folks chalk this off to
'Lightning' ... in reality it is not, it is due to Tower Ground, Bldg
Ground and Power Ground being at a different potential causing current
to flow thru the ground wires etc.
:)
Faisal Imtiaz
Snappy Internet & Telecom
7266 SW 48 Street
Miami, FL 33155
Tel: 305 663 5518 x 232
Help-desk: (305)663-5518 Option 2 or Email: supp...@snappytelecom.net
------------------------------------------------------------------------
*From: *"George Skorup" <geo...@cbcast.com>
*To: *af@afmug.com
*Sent: *Wednesday, December 30, 2015 12:15:33 AM
*Subject: *Re: [AFMUG] WISP insurance
For about a month at one site during the summer (maybe last year,
I don't remember, too much shit in my head), we got a bunch of
popped fuses and surge suppressors. Our local 911 dispatch joined
the site months before and we didn't have any problems. We finally
figured out that the grounding sorta got split. Everything was
still interconnected, just not optimally. So we all made sure that
everything was tied to a single point, aka R56. No more issues. We
do still get some popped fuses once in a while, but that's mostly
Chuck's surge suppressors clamping on nearby lightning strikes.
I'd rather have that than dead or degraded ethernet ports.
It was also a very wet spring and then things dried out. We've
noticed this pattern for >10 years. If the soil is pretty dry for
a lot of the year, we lose more gear. Which brings up another
point. Up to a couple years ago, we had a site where we'd lose
everything 2-3 times per year. The power company came out and ran
a load test at our transformer. 20A is all it would do. The ground
rod at the pole/transformer was almost completely gone. I think
they said there was maybe 2 feet left and they pulled it out by
hand. Of course it was probably 40 years old.
On 12/29/2015 10:28 PM, Jaime Solorza wrote:
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.
