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Author Topic: Lightning Protection???  (Read 4880 times)

Cailen Waddell

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Lightning Protection???
« on: March 12, 2014, 09:54:20 am »

Hi all,

This may be the wrong place for this... so move if appropriate.

The situation - we have a Softball complex, 4 fields, arranged like a pie, with a central tower.  Tower, has audio control, amplification, and 4 announcer positions, for each field.  Speakers are 70v and located on light poles.

An aerial view is available here: https://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=Middle+Creek+Softball+Fields,+Apex,+NC&aq=0&oq=middle+creek+sof&sll=35.770436,-78.830308&sspn=0.522019,1.056747&vpsrc=6&t=h&ie=UTF8&hq=Middle+Creek+Softball+Fields,+Apex,+NC&ll=35.667373,-78.762982&spn=0.005775,0.008256&z=18&iwloc=A&cid=15816722727301953307

The complex has had the audio system completely destroyed twice, by what I am told is lightning - this is my first time being involved in it.  There are certainly confirmed lightning hits during storms to the light poles.... 

Regardless, I think there are two things going on, one is speakers are damaged because there isn't enough rig for the gig.  2 Currently each field is fed by a 70v mixer amp.  It is my theory that when a pole is struck by lightning, the power is traveling back up the speaker line and hitting the amp - maybe grounding out through the rack and touching the other amps?  They also have one shared input each, that is fed through an xlr splitter (not my install) so there is a signal connection between them there...  Is this far fetched?  It could be that the surge from the lightning strike is traveling somehow through the shared transformer for the complex and going out to equipment?  I'm grasping at straws here a little bit.  Should I be bringing in an electrician?  I can put the system on a good ups but that won't provide any protection from lightning really.   Can I fuse the speaker lines?  Trying to find a solution before we pour some money on this - it may be that this is well beyond what anyone can diagnose via the internet, and thats cool, I am hoping to get some direction so if we have to hire a contractor to look at things, I have enough knowledge to know if we are being fed a line of bullshit.

Full disclosure/disclaimer: I am the production supervisor for the municipalities arts center, I am well versed in installs and code, and have a great relationship with the AHJ.  I am very comfortable performing audio installation work here, and while we do hire out bigger systems, the smaller ones we work on ourselves....  This however, and the lightning (or claimed lightning) is a little out of my comfort zone.

I intend to replace the 4 mixer amps with a single Ashly PEMA 4 channel 70v amp.... and with some judicious signal processing, hope to help stop the 'not enough rig for thei gig'  but that is for another thread...
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Mike Sokol

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Re: Lightning Protection???
« Reply #1 on: March 12, 2014, 10:18:47 am »


The complex has had the audio system completely destroyed twice, by what I am told is lightning - this is my first time being involved in it.  There are certainly confirmed lightning hits during storms to the light poles.... 


I'm the moderator here, and I think this is a perfect question for this forum. But give us a little more intel first. When you say "completely destroyed", what exactly do you mean. Did the diaphragms burn out of the horns, or was everything melted down. Did the power amp(s) just have their output transistors fried, or was there visible lighting damage with melted CB traces, etc... A little postmortem analysis can point you in the right direction.

I personally have done a lot of studying about lighting damage to buildings and AVL systems, and I know there are others on this forum who've had lightning experience as well. So we should be able to come up with an educated guess.

Also, note that proper ground-rod impedance is extremely important to reducing lightning damage. Without a solid (under 25 ohm) earth-ground connections, then side-strikes can occur inside of equipment anytime there's a nearby lightning strike in the area. At the very least I would hire an electrician and ask for a "fall of potential" test of the ground rod impedance. Failing that, I would add a new ground rod in parallel with your existing one, making sure it uses heavy copper wire (#6) without any sharp bends in the hookup.

For very large/outdoor ice-rink installations we've done fiber-optic hookups from the mix position to the various speakers out in the field. I don't know if anyone makes a self-powered paging horn for outdoor use, but if they had something self-contained with an S/PDIF input on TosLink, that would be the best possible scenario since you've eliminated the antenna effect of all that copper stretching around. Also, is the speaker wire underground, in metallic conduit, or flown in the air pole-to-pole?

Anything else you tell us about the existing installation will help with the diagnostics.
« Last Edit: March 12, 2014, 10:36:39 am by Mike Sokol »
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Stephen Swaffer

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Re: Lightning Protection???
« Reply #2 on: March 12, 2014, 10:36:35 am »

Years ago I worked with a communication provider and one of the things we did was phone systems. In one facility with multiple buildings we had trouble with lightning taking out phones and controllers.  We installed fuses on a 66 punch down block that took car of the problem.  I would think something like that might help-a very fast acting fuse sized maybe 2 times the expected current-probably not much on a 70 V line.

Might not be "the solution", but might be an inexpensive precaution to use as part of a complete fix.
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Steve Swaffer

Cailen Waddell

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Re: Lightning Protection???
« Reply #3 on: March 12, 2014, 10:42:54 am »

Quote
Are you suggesting ground rod testing on the power for the complex or testing of the lighting protection on the towers?  The fixtures on the light towers are not blowing (I'm told). But the control electronics are damaged)

I'm suggesting ground rod testing for the complex. I worked at a church in Texas a few years ago with a large metal cross on the roof of the building that was grounded to the building's safety-ground, rather than it's own ground rod. A very close lightning strike burned up a lot of A-V gear, but also did something interesting to the building's ground rod. I predicted something I now call Popsicle-fication which is when a lighting strike forms a glass-sheath on the ground rod in sandy soil. Now the electrical ground-plane of the building was floating around, which we measured at 40-volts AC above actual earth potential. The other hint was that their lighting guy said he could feel a tingling in his finger tips from the console whenever he saw lightning in the clouds. Essentially they were doing the Ben Franklin kite experiment with their own building's electrical system. I'm now of the opinion that after a building has had a direct or very near lightning strike, that a fall-of-potential ground-rod test should be performed to confirm ground rod integrity. One of the most important aspects of ground-rods is lightning strike shunting to earth. Once a ground rod is damaged due to corrosion, melted wiring, or Popsicle-fication in sandy soil, then you're a target for any nearby lightning strike.
« Last Edit: March 12, 2014, 11:00:37 am by Mike Sokol »
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Jonathan Johnson

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Re: Lightning Protection???
« Reply #4 on: March 12, 2014, 01:42:33 pm »

A very close lightning strike burned up a lot of A-V gear, but also did something interesting to the building's ground rod. I predicted something I now call Popsicle-fication which is when a lighting strike forms a glass-sheath on the ground rod in sandy soil. ... Once a ground rod is damaged due to corrosion, melted wiring, or Popsicle-fication in sandy soil, then you're a target for any nearby lightning strike.

There's a term for this: Fulgerite.
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TJ (Tom) Cornish

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Re: Lightning Protection???
« Reply #5 on: March 12, 2014, 01:52:45 pm »

There's a term for this: Fulgerite.
Popsicle-fication is more fun, though.
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Mike Sokol

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Re: Lightning Protection???
« Reply #6 on: March 12, 2014, 02:32:46 pm »

Popsicle-fication is more fun, though.

Popsicle-fication is also more descriptive, I think...  8)



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Mike Sokol
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Re: Lightning Protection???
« Reply #6 on: March 12, 2014, 02:32:46 pm »


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