IPVMU Certified | 08/05/16 02:47pm
In general, there's not much you can do to prevent lightning from destroying the stuff it directly strikes. Millions of volts is hard to tame.
What you can and should do is use lightning arrestors and surge protection to isolate the damage.
For example, lightning arrestors at the camera can't help the struck camera from becoming burnt toast, but they trap the surge from traveling down the cable and wrecking the switches/traveling to other cables/cameras, etc...
Our guide on Lightning Protection for Surveillance Cameras will help here.
There are preventative measures that can be taken. When we install microwave radios on towers we refer to the Motorola R56 Standards and Guidelines. While this is specifically for towers it has excellent theory and when we install to those guidelines we rarely have a failure due to lightning. Most important is to establish a good ground, with multiple buildings this can be a challenge. (If the metal buildings were installed correctly then the structure is grounded and the structure should be bonded to electrical ground) Once you have established a "ground" you can run quality shielded cable and bond it to ground (no ground loops!). Once you have that then lightning protectors are quite effective at protecting the expensive equipment. Of course you can install protectors and replace them every lightning strike but that isn't very cost effective and often ineffective. Lightning will take the path of least resistance so the theory is to provide a path (via shield of cable) to ground that leads away from expensive equipment.
Chesapeake & Midlantic | 08/08/16 01:42pm
You could tell him to apologize to the witch he ticked off. Maybe she'll lift her curse.
Seriously, though. Instead of mitigating, how about diverting? Install a lightening rod on a tower and draw lightening away from fragile electronics, grounding harmlessly into the earth instead.
IPVMU Certified | 08/08/16 02:01pm
Forget copper wire FIBER is your answer
In my neck of the woods we see this problem ALOT. This year has been particularly bad, as we are now working our 5th major lightning call in as many weeks. Most of these are EM induction issues that have primarily affected data and alarm networks, but 2 were direct hits. In one of these cases the existing tower to which we affixed our P2P was no longer grounded (verified with voltmeter after the fact) and the strike zapped everything. Any I mean everything. We had shielded cable, and the strike walked through 3 levels of APC data line protection with proper grounds without slowing down. Proper grounding at the tower would have helped, but I don't know how much.
Our second direct hit was residential, and there was some fiber in place, but given that it literally blew a hole in the side of his house I don't think there is a level of protection that would have helped.
One of our biggest hits was an EM on large site with 4 buildings, separated by over 3000'. The buildings have exclusively fiber interconnects, yet all 4 were hit. Anything not plugged into a surge was killed, and all the data lines were affected. Interestingly, one of the buildings did have data surge protection at the switch side, but it only saved the switch and not anything station side. Even more fascinating was that the analog cameras were unaffected, although the dvr nic was fried.
All of these clients were offered more protection, yet declined due to the cost increase vs. paying insurance premiums. The last site is installing lightning rods, but I'm not convinced this won't make the problem worse. We learn a bit more about what works and what doesn't every time, but at the end of the day all I can is "nature be scary".
I'm curious if anyone in the group here has crunched the numbers and created a business case for surge suppression. We designers often receive push-back from internal and external stakeholders about the additional cost that surge suppression adds to a solution given the relatively low frequency of lightning strikes.
Consider a PTZ camera out on a pole with a media converter in an enclosure at the base and fibre optic to head end network equipment. The most valuable component, the PTZ camera, is toast in a lightning strike, though we are able to protect the media converter. Given the frequency of occurrence, the dollar value of equipment actually protected (the media converter, in this case), and the quantity of equipment out in the field requiring surge suppression, can you make a case based on cost alone to include surge suppression in outdoor surveillance designs? Or is the scale of risk vs reward tipped the other way around?
Proper Bonding, Grounding, Isolation of power circuits , shielded wiring
1st you need to have good lightning protection and Isolation on the circuits
Then You need great Drains on the circuits and wiring to ground. Solid connections
Good Lightning Rods, 8-12 ' min. depth , with multiple paths for drain. Good Grid
Lightning is 80kvlts /sec / inch on discharge.
Missile defense systems all over the world have great systems in place.
I was in power protection for 20 years and Yes you can achieve this , But it cost $
No Cheep fix.
Every Motor, creates dirty power, many other sources on the circuits constantly hitting the systems
what part of the country are you in? I would recommend calling your local Ditek rep(disclosure: I am a rep for Ditek). Ditek specializes in surge suppression; we may not save the direct strike, but we can sure help spare the rest of the system. What type of system is it?
Pro Focus LLC | 08/17/16 11:47am
I have a residential customer who has been hit two years on a row. Neither were direct hits. The strike actually hit a neighbors tree the first time, about 500' away from his house.
This time, I'm unsure where it hit, but he claims it was in the same neighbors yard somewhere.
This customer has a Dahua CVI system. His outdoor cams are mounted around the house on the soffits, which are metal.
Both times, the storm has taken out the same two cameras on the side of the house nearest to the strikes. The damages have been contained to just the cameras (and a TV in the room under the soffit) and hasn't traveled up the wire to damage anything at the head end.
I am wondering if this damage is caused by static in the air from strike? If so, how could this be prevented, short of a faraday cage?
Called Ring-wave , effects of lightning breaking thru the air and static discharge is result.
Most high end cameras now have built in cat 6 shielded connections and grounding , and bonding jumpers for this discharge.
If you have a direct Hit , the only way to protect it is a lightning arrester with @ least #4 copper bonded to earth ground. not emt with connections , any splice, or bond pt is the weak link .
Best is soldered connections
We completed a Power sub station and have 6 cameras on poles surrounding the facility and have had no problems with 160k power lines crossing in every direction . 20' from lines .
So you see the problem is not the lightning but the discharge path to ground.
Shielded cabling question, thought this was a good discussion for it. I've been told to only connect the drain wire on one end, does it matter which end?