There is a ground testing method called the “decline of potential” or “fall of potential”. You can do it with three ground rods, 100’ of cat 5 and a car battery. In any event, you measure the resistance of your grounding systems. If it is not low enough you keep adding ground rods until it is.
I have had to do this test for mining operations to make MSHA happy. Fluke makes a nice special meter for this but you really don’t need it if you can measure volts, amps and have a car battery somewhere nearby. http://www.fluke.com/fluke/inen/solutions/earthground/fall-of-potential From: Joshaven Mailing Lists Sent: Wednesday, December 30, 2015 10:28 AM To: af@afmug.com Subject: Re: [AFMUG] WISP insurance This is good stuff. When replying I was worried that I was gonna get smeared for being that little voice in the background that keeps bringing up the grounding discussion. It seems to always be the story that operators already have things grounded “properly” yet keep getting destroyed by surges. I would say that almost every tower I have visited has been poorly grounded. A friend of mine who travels the country fixing issues for AM, FM & TV stations says the number one issue is grounding. (I’ve picked his brain quite a lot to validate my opinions on this issue and owe much of my understanding to him.) Interestingly he also says that in some cases he has had to drive a well into the water table to get an adequate ground to fix sensitive locations. So if your gauge of proper grounding stops at a 10’ rod next to the tower and you are still having problems then don’t dismiss the grounding question too easily. 10’ into a layer of dry sand won’t fix your issue especially if you have split grounds like discussed below. Sincerely, Joshaven Potter Google Hangouts: j...@g2wireless.co Cell & SMS: 1-517-607-9370 supp...@joshaven.com On Dec 30, 2015, at 12:06 PM, Chuck McCown <ch...@wbmfg.com> wrote: You have two or more grounding circuits that are not bonded together properly. Say one circuit for the tower and radio gear that goes into some ground rods and then the power company with their neutral and ground circuit. If those two are not tied together with a very low impedance heavy duty connection you will generate a large voltage difference during strikes. I prefer the PANI grounding system that the telco world uses. Combine that with a halo /franklin system and I really do not know how much better you can do it. Perhaps put up some ground towers like NASA does surrounding the space craft on the launch pad. -----Original Message----- From: Jay Weekley Sent: Wednesday, December 30, 2015 9:53 AM To: af@afmug.com Subject: Re: [AFMUG] WISP insurance What is split grounding? Faisal Imtiaz wrote: 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.
