I have always believed most surges come in on the power, not via the tower.
But the tower and building grounding are where they are looking to go and once
they get into a weak grounding circuit they hit everything.
From: Faisal Imtiaz
Sent: Wednesday, December 30, 2015 8:25 AM
To: af@afmug.com
Subject: Re: [AFMUG] WISP insurance
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> 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
Help-desk: (305)663-5518 Option 2 or Email: supp...@snappytelecom.net
--------------------------------------------------------------------------
From: "Glen Waldrop" <gwl...@cngwireless.net>
To: 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
Sent: Tuesday, December 29, 2015 4:57 PM
To: 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
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 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
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.
