Having a problem with continued Camera location being Zapped when a storm goes by. Over the past couple of years have had to replace a single camera location with new units after a storm. About six(6) cameras at this point. There are 2 cameras in this building. The other camera had been zapped as well before the surge protection and ground rod was installed. Since then it just the one that has had the continued problem. The cameras are about 40 feet apart.
The following are the other particulars.
It has always be the video side of the camera that has been hit.
> Building is separated from main building by about 200' of underground PVC > conduit.
> Cable RG59
> Have installed at the building Ditek Surge Protector DTK-VSPBNCA. One at
> each camera.
> Ground Rod installed within 50' and #12 Ground wire to Protector
> Camera Powered locally with Wall Wart 24vac
I know that this may be impossible but the main question is, what can be done to stop this from happening??
Is there a better surge/spike protector??
> Would a second ground rod help??
> Would it make a difference if the camera was powered by 12vdc??
> Is there a way to determine the weak point of the system??
Thanks for any thoughts or suggestions that would be helpful.
You can do separate ground rod *if* you configure the cabling 'correctly' [I know, sounds circular where 'correctly by definition means it keeps on working. But, what I refer to is more like RF/ Microwave type construction techniques. For example, a connection between two points is only a connection making the two points equal voltage *IF* it's wider than long, else it's an inductor. An inductor is likely to hold ALL the voltage across it for a little bit of time, so you see, it's NOT a connection in the sense same voltage]
There are several firms that sell robust lightning protection add- oons, but can't find fast enough.
Do you want to purchase and install, or do you want to learn a bit and buy the bits and pieces yourself and modify the site yourself?
Here is a list of references kindly provided 2009 by Mick Matum of the IEEE EMC group:
COPIES
2008
160. "Initial-stage pulses in upward lightning: Leader/return stroke versus M-component mode of charge transfer to ground", Geophys. Res. Lett., 35, L13812, doi:10.1029/2008GL034148, 2008, 5 p., D. Flache, V.A. Rakov, F. Heidler, W. Zischank, and R. Thottappillil
156. "Influence of strike object grounding on close lightning electric fields", J. Geophys. Res., 113, D12109, doi:10.1029/2008JD009811,
2008, 18 p., Y. Baba, and V.A. Rakov
154. "X-rays from 80-cm long sparks in air", Geophys. Res. Lett., 35, L06805, doi:10.1029/2007GL032678, M. Rahman, V. Cooray, N.A. Ahmad, J. Nyberg, V.A. Rakov, and S.R. Sharma
149. "Distribution of currents in the lightning protective system of a residential building: II. Numerical modeling", IEEE Trans. on Power Delivery, in press, L. Li and V.A. Rakov
147. "Lightning-induced currents in a buried loop conductor and a grounded vertical conductor", IEEE Trans. on EMC, Vol. 50, No. 1, February 2008, pp. 110-117, J. Schoene, M.A. Uman, V.A. Rakov, J. Jerauld, B.D. Hanley, K.J. Rambo, J. Howard, and B. DeCarlo.
146. "Pulse trains characteristic of preliminary breakdown in cloud-to- ground lightning that are not followed by return stroke pulses", J. Geophys. Res., 113, D01102, doi:10.1029/2007JD008489, 2008, A. Nag and V.A. Rakov
145. "Applications of Electromagnetic Models of the Lightning Return Stroke", IEEE Trans. on Power Delivery, Vol. 23, No. 2, April 2008, pp. 800-811, Y. Baba, and V.A. Rakov
143. "On representation of lightning return stroke as a lossy monopole antenna with inductive loading", IEEE Trans. on EMC, Vol. 50, No. 1, February 2008, pp. 118-127, S. Bonyadi-ram, R. Moini, S.H.H. Sadeghi, and V.A. Rakov
2007
142. "Lightning strikes to tall objects: currents inferred from far electromagnetic fields versus directly measured currents", Geophys. Res. Lett., 34, L19810, doi:10.1029/2007GL030870, 2007, Y. Baba, and V.A. Rakov
141. "Expressions for far electric fields produced at an arbitrary altitude by lightning return strokes", J. Geophys. Res., 112, D16102, doi:10.1029/2007JD008559, 2007, R. Thottappillil, V.A. Rakov, and N. Theethayi
140. "Electromagnetic fields at the top of a tall building associated with nearby lightning return strokes", IEEE Trans. on EMC, Vol. 49, No. 3, August 2007, pp. 632-643, Y. Baba, and V.A. Rakov
139. "Insights into the ground attachment process of natural lightning gained from an unusual triggered-lightning stroke", J. Geophys. Res.,
112, D13113, doi:10.1029/2006JD007682, 2007, J. Jerauld, M.A. Uman, V.A. Rakov, K.J. Rambo, and G.H. Schnetzer.
You can do separate ground rod *if* you configure the cabling 'correctly' [I know, sounds circular where 'correctly by definition means it keeps on working. But, what I refer to is more like RF/ Microwave type construction techniques. For example, a connection between two points is only a connection making the two points equal voltage *IF* it's wider than long, else it's an inductor. An inductor is likely to hold ALL the voltage across it for a little bit of time, so you see, it's NOT a connection in the sense same voltage]
There are several firms that sell robust lightning protection add- oons, but can't find fast enough.
Do you want to purchase and install, or do you want to learn a bit and buy the bits and pieces yourself and modify the site yourself?
Here is a list of references kindly provided 2009 by Mick Matum of the IEEE EMC group: ===================================================
Robert,
I don't mind learning something new, do it every day. I have always be fascinated with lightning as to its effects and potential. However not to the point of wanting to write a thesis on the topic. More importantly here is I want to find out what is needed to correct this problem at this location that seems to be most unique.
Thanks for the technical theory link. I will read some of it someday.
I get the idea that the grounds are the problem and that some additional connections need to happen to some additional devices. Already have done enough experimenting but have had no success with a cure. I have also determined that not every fix works in every application.
You have reasonable intelligence, right? If the 'expert' can't explain it to you, THEY DON'T KNOW IT very well!
Translating all that theory into 'practical' ...Remember lightning is HIGH FREQUENCY! We're talking over 100MHz with most of the energy centered in the 1? 3? or sometimes 10 MHz range. Your AM Radio stations are in the 1MHz range.
Next lightning is HIGH VOLTAGE [as if you didn't notice] but it also has a lot of backup so it will supply oodles of current if there is an 'arc over' [in the 10,000++ Amp range - and during that short circuit discharge all the current pretty much flies through all at once, remember your house runs nicely on a 200A breaker box with only
220Vac, so you catch the drift of just how much power is there]
To kind of envision what a lightning strike is like, picture the earth as a giant rubber sheet that is all at ground potential lying flat. Suddenly lightning strikes the ground, which is like reaching down and pinching the rubber sheet in that spot and pulling it 'up' to very high potential. See how you made a teepee? Well that slope represents the voltage gradients from the strike down to where the voltage is again zero.
Now if the strike is energetic enough the difference in voltage between two points, even if they're close together, can be substantial. That's why four legged animals don't survive as well as two legged animals with feet together huddled into a ball. New thinking is don't lie flat.
Now back to your cameras. With a strike, or even a slight sizzler, one building ground is at one potential and 200 feet away the other building ground is at another, notice BIG voltage difference. But wait, you've got a great conductor, camera cabling, tieing between the two buildings! Just imagine what those cameras feel like with, say, ground on the coax cable and their power supply leads are 10,000 volts higher. Big ouch, or at least potential for a big ouch.
How to fix? This gets a bit tricky. The best way to fix the problem is to filter out all that bad stuff. Think how multi-stage filters stop a signal. First you have a short to ground, then in series a high impedance, and then another low impedance to ground, and so on. So you have good ground at building A and another good ground at building B, but you do NOT have a high impedance between the buildings! How to do that? Buy tons of clamp on ferrites. Clamp along the cabling connecting the two buildings. Make certain [if possible] to clamp about every foot along the cable bundle and include ALL the cables as you clamp each ferrite on. There is probably good bypassing [capacitance between +/- input and the coax itself is good. Don't know about what power to coax is like. But you may not have to add anything there.
So now here's how your 'protection' works. building A and building B are NOT at the same potentential, BUT! because of all those ferrite clamps as you go along the bundle of cabling the voltage variation pretty much makes a nice uniform transition from A to B WITH the relative voltages staying pretty close to each other. Thus, nothing zaps the camera, because your structure can't create 10,000 volt difference between power and coax. Maybe only a couple hundred volts.
Sadly, ferrite clamps start becoming an impedance as you go up in frequency, like at 50-100MHz, so one has to increase that impedance by 'looping' the cabling around at least once, more than three times kind of gets counter productive. But the problem with looping is that it provides a path bypassing the ferrite core just where the cable turns on itself and gets close [remember the 100MHz energy?] this provides an arc path. so some people use giant torroids to loop the cable around for the low frequency energy and right near that point they clamp a ferrite, making the protection a bit more 'broadband'.
I know this is simplistic, but a place to start. You're not losing a camera EVERY time, so perhaps this small amount of 'fix' will suffice.
You have reasonable intelligence, right? If the 'expert' can't explain it to you, THEY DON'T KNOW IT very well!
Translating all that theory into 'practical' ...Remember lightning is HIGH FREQUENCY! We're talking over 100MHz with most of the energy centered in the 1? 3? or sometimes 10 MHz range. Your AM Radio stations are in the 1MHz range.
Next lightning is HIGH VOLTAGE [as if you didn't notice] but it also has a lot of backup so it will supply oodles of current if there is an 'arc over' [in the 10,000++ Amp range - and during that short circuit discharge all the current pretty much flies through all at once, remember your house runs nicely on a 200A breaker box with only
220Vac, so you catch the drift of just how much power is there]
To kind of envision what a lightning strike is like, picture the earth as a giant rubber sheet that is all at ground potential lying flat. Suddenly lightning strikes the ground, which is like reaching down and pinching the rubber sheet in that spot and pulling it 'up' to very high potential. See how you made a teepee? Well that slope represents the voltage gradients from the strike down to where the voltage is again zero.
Now if the strike is energetic enough the difference in voltage between two points, even if they're close together, can be substantial. That's why four legged animals don't survive as well as two legged animals with feet together huddled into a ball. New thinking is don't lie flat.
Now back to your cameras. With a strike, or even a slight sizzler, one building ground is at one potential and 200 feet away the other building ground is at another, notice BIG voltage difference. But wait, you've got a great conductor, camera cabling, tieing between the two buildings! Just imagine what those cameras feel like with, say, ground on the coax cable and their power supply leads are 10,000 volts higher. Big ouch, or at least potential for a big ouch.
How to fix? This gets a bit tricky. The best way to fix the problem is to filter out all that bad stuff. Think how multi-stage filters stop a signal. First you have a short to ground, then in series a high impedance, and then another low impedance to ground, and so on. So you have good ground at building A and another good ground at building B, but you do NOT have a high impedance between the buildings! How to do that? Buy tons of clamp on ferrites. Clamp along the cabling connecting the two buildings. Make certain [if possible] to clamp about every foot along the cable bundle and include ALL the cables as you clamp each ferrite on. There is probably good bypassing [capacitance between +/- input and the coax itself is good. Don't know about what power to coax is like. But you may not have to add anything there.
So now here's how your 'protection' works. building A and building B are NOT at the same potentential, BUT! because of all those ferrite clamps as you go along the bundle of cabling the voltage variation pretty much makes a nice uniform transition from A to B WITH the relative voltages staying pretty close to each other. Thus, nothing zaps the camera, because your structure can't create 10,000 volt difference between power and coax. Maybe only a couple hundred volts.
Sadly, ferrite clamps start becoming an impedance as you go up in frequency, like at 50-100MHz, so one has to increase that impedance by 'looping' the cabling around at least once, more than three times kind of gets counter productive. But the problem with looping is that it provides a path bypassing the ferrite core just where the cable turns on itself and gets close [remember the 100MHz energy?] this provides an arc path. so some people use giant torroids to loop the cable around for the low frequency energy and right near that point they clamp a ferrite, making the protection a bit more 'broadband'.
I know this is simplistic, but a place to start. You're not losing a camera EVERY time, so perhaps this small amount of 'fix' will suffice. =====================================================
LOL Buying tons of clamp on ferrites is not in the future.
At this point re-evaluating the current grounding should be the first step. Need to get there before the next storm goes through. Oh, to late, that just happened earlier this evening.
Ok, I know something needs to be do with the grounding. And, I get the points you are making. However, I find it a little challenging on what it is going to take to ground a plastic camera case.
Thanks for the input.
BTW what is with all the CRAP at the bottom of your post?? I did a little edit. No need to repeat it all.
Like most cameras today with dual voltage 12vdc or 24vac there is only a two wire connection. And then the video output with a BNC coax connector.
The ground rod was has a clamped on #12 that goes to the Ditek video protector.
I am thinking this is where the biggest problem is at. Initially there was no protection. Camera got zapped. Then added the protector and connected to building ground. When that camera got zapped then added the ground rod and connected to it. The last couple of cameras have been connected in this way with a lot of puzzled looks. Something needs to be changed that is why I am seeking some additional thoughts on the issue.
There is always the thought of a Faraday Cage over the whole complex, but that just seems a bit extreme. :-)
Almost EVERY one of my clients whose products have problems with EMC and passing all those pesky legal requirements so their products can't be sold asks me the same thing, "Fix it, but we're ready to go into production, so don't change anything."
hen a storm goes by. Over the past couple of years have had to replace a si ngle camera location with new units after a storm. About six(6) cameras at this point. There are 2 cameras in this building. The other camera had been zapped as well before the surge protection and ground rod was installed. S ince then it just the one that has had the continued problem. The cameras a re about 40 feet apart. The following are the other particulars. > It has a lways be the video side of the camera that has been hit. > Building is sepa rated from main building by about 200' of underground PVC > conduit. > Cabl e RG59 > Have installed at the building Ditek Surge Protector DTK-VSPBNCA. One at > each camera. > Ground Rod installed within 50' and #12 Ground wire to Protector > Camera Powered locally with Wall Wart 24vac I know that thi s may be impossible but the main question is, what can be done to stop this from happening?? > Is there a better surge/spike protector?? > Would a sec ond ground rod help?? > Would it make a difference if the camera was powere d by 12vdc?? > Is there a way to determine the weak point of the system?? T hanks for any thoughts or suggestions that would be helpful. Les
I don't know much .... let me be honest, .... next to nothing about lightni ng abeyance but you said it's always on the video side.
I think I saw some of your work the other day. But, why did you use all the white zipties as opposed to black?? Oh, it would much better if you cut the tails off to give a finished look.
surprisingly enough, we've had the same kind of problem you described originally.. Our "fix", least wise it's stopped 99% of all replacements , was to float the long runs of coax above ground.. (no grounding at the camera end) use double surge/lighting arrestors, one at the entry point to the primary building another at the recorder.
Our thinking was to reduce or remove the current/voltage surge between grounds, and only deal with the transients air born antenna effect.. so far (3 years) its been working..
NOTE: you'll need to check the surge protectors after any events at the building location.. (you might stop the first one but if its damaged the next strike will get your cameras again..)
Ideally, you should run your Cat 5/6 in buried METAL conduit between the buildings, with Transient Surge protection at both building entry points which are ground bonded to the structures ground system.. (ie... the electric code NFPA 70 or IBC)
But unless it?s a new construction, good luck with that..
Interesting!! I can see that being an answer in the right application. Here it is 250 feet between buildings with no poles to support the coax. That is not with out planting a few to see if they grow. The metal conduit comment is interesting as well and make sense. May seriously consider for the next project. This one is doubtful.
As for "checking the surge protectors after". How do you do that?? I have been thinking on the same thing but how does one actually test the dang thing?? As I understand they are to auto reset unless they are blown and nothing works. I am thinking more towards just throw away and replace. One of my bigger questions is who makes a better unit for coax?? or what model or specs should one look for to get the best?? Some spec that they respond in 3-5 nanoseconds. Electrical current travels at the speed of light or
186,000 miles per second. With a little math that would mean that a nanosecond is equal to 11.8" inches. At 3-5 nanoseconds the current will travel 35.4" to 59" before it is clamped to ground. I try and put at least that much cable or wire between the protector and the device. Don't know if that really helps but in this project it has not.
I will shop around for some starter poles and get them planted. Maybe by the time I get this problem resolved they will be tall enough to hang some wire on.
Robert Macy's reply was spot on. Others misunderstood some of his points . For example, conduit or other grounds that are that long are (essentiall y) non-existent. For surge protection, even length of a wire is critical. Even a sharp wire bend compromises protection.
To resummarize his points. Your camera 200 feet away must be handled as if two completely different structures. Using the same protection method i mplemented between your home and the telco's CO. Each structure must have its own single point earth ground. Camera will never be earthed by the buil ding's ground. Otherwise, a lightning strike to one building (ie the house) is a direct lightning strike to electronics in the other structure (video section of a camera).
Do not earth the camera. That makes a camera the better and destructive connection to earth. Earth every incoming conductor to that camera. And a gain, the earthing must be low impedance - as short as possible (ie 'less t han 10 feet').
This professional's application note demonstrates the concept - The Need for Coordinated Protection:
formatting link
In your case, replace that antenna tower with a camera. The tower and bu ilding both have their own single point earth ground (all four words are el ectrically significant). Any wire that enter the building or camera must f irst connect to earth ground. Either directly (ie the shield of a coax) or via a protector (ie 12 VDC). If any one wire in any cable violates that r ule, then damage can result either to electronics inside the building or ca mera.
Also important. Makes no difference if the wire is overhead or undergrou nd. Same rules apply as that application note says.
Do not earth a camera. Earth the surge. A major difference. Even joint s in conduit compromise protection. If a ground wire is inside a metallic conduit, then it also does not earth a surge. It is not about wire thickne ss. Most critical is conductor 'length'. No splices. No sharp wire bends. Otherwise impedance is too high - the earth ground connection all but does not exist.
A surge is electrically different from electricity that powers appliances . Even wires must be routed with greatest care. Protectors are simple sci ence. Most important is the art of protection - single point earth ground.
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