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 <gwl...@cngwireless.net> > *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 <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 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. > > > > > >
