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Lightning delays, what's the deal?


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I am just curious about this and I don't care if I sound dumb - what is the danger?  Have gennies actually been hit and exploded, killing people?  Why would a generator "draw" lightning at all?  Doesn't the lightning seek to release its voltage differential to the closest neutral AKA the earth?  Or is a genny neutral?

 

I did hear a verified account of a genny that was hit during a storm in FL.  They didn't stop shooting for the storm and then the lights went out.  No one died but I'd guess the genny was a goner.  But in that case, lightning was striking all over the area, including many hits NOT on the genny. I'm confused.

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Electricity will take the shortest path between the highest voltage differential.  If the clouds have a negative charge and the genny contains positive voltages, that would make the genny a slightly more likely target for a strike relative to "neutral" ground, though the hundreds of volts in a genny probably don't make too much of a difference compared to the tens of thousands of volts in the cloud.

Bear in mind that voltage is a differential, so there's no such thing as truly "neutral" ... just neutral relative to the surroundings (which, if you have a thundercloud overhead, is by definition a different voltage).

I'm no genny op, but I would imagine that lightning delays have more to do with protecting all the equipment that is attached to the genny (not to mention the people in proximity to that equipment).  A lightning strike will energize any and all circuits connected to its strike (barring voltage protection equipment, which may or may not be adequate protection), which has the potential (pun intended) to create electrocution hazard in any device that is connected to the genny.

So, if I were to guess, lightning delays are probably done in the interest of protecting crew (especially lamp ops) from electrocution.  But I live in an area where lightning delays aren't a thing, so what do I know?

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16 minutes ago, The Documentary Sound Guy said:

Electricity will take the shortest path between the highest voltage differential.  If the clouds have a negative charge and the genny contains positive voltages, that would make the genny a slightly more likely target for a strike relative to "neutral" ground, though the hundreds of volts in a genny probably don't make too much of a difference compared to the tens of thousands of volts in the cloud.

Bear in mind that voltage is a differential, so there's no such thing as truly "neutral" ... just neutral relative to the surroundings (which, if you have a thundercloud overhead, is by definition a different voltage).

I thought the regular dirt earth is basically neutral?  And further, how would a genny be unbalanced?  It's a wheel spinning spools of wire around magnets, so wouldn't positive and negative be equally generated?
 

I am a total dummy and I'm trying to learn this kind of stuff as the questions come up, not the best way...  Where's Blankenship when you need him?!!

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"Earth" is neutral because it's the prevailing environment, and also because, in many cases, we ground our devices to earth, which equalizes the voltage of our equipment to the earth.  So, it's neutral because we decided to make it neutral and designed our equipment to treat it as such, not because it's inherently zero volts.  There's no such thing as zero voltage in absolute terms; any voltage we measure is a difference in potential between two points.  Importantly, it's also neutral relative to *us*, because we are constantly making contact with it, but even then, it's not true 100% of the time.  Every time you get a shock from static electricity, it's because your skin is at a different voltage compared to the thing you touched.

And yes, maybe a genny would be balanced on average ... it's a bit beyond my understanding to say definitively.  Certainly, the outside casing would be at the same potential as earth, otherwise it would be an electrocution hazard.  But, internally, there are certainly voltage differences, and it seems plausible to me that one of those internal voltages could attract a strike.  Or maybe the outside casing would insulate it and prevent that ... but if we are talking a difference of tens or hundreds of thousands of volts, I kind of doubt the casing would present much of a barrier (though, it would conduct current away from the internal components before the strike reaches them, probably melting in the process).  In lightning, we are talking about voltages that are high enough that air conducts electricity, so the air gap that electrically separates the internal generator components from the outside casing is close to meaningless for a lightning strike.

As I hope you can tell, I'm trying to answer your question about whether a genny would attract lightning through guesswork based on my understanding of electricity, but I'm not authoritative here.  I suspect the answer to whether it would attract strikes is "only slightly, at worst", but we probably want to talk to a meteorologist.  Or a genny op.

I stand by my original answer, which is that downstream electrocution risk is the determining factor for taking lightning breaks, not the increased risk, if any, of the genny attracting strikes.

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Oh yes I agree that's the stated purpose - to avoid frying gear and people - but my question is how often does that happen?  I did ask the genny op and he had never heard of a genny being struck.  Neither had the few other juicers.  It was a camera op who had the FL story.

 

We just lost four hours and wrapped early because of this haha!  I just want to understand. 
 

I appreciate your postings!

 

Dan

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On shows I've been on (or just out in the world) it was stressed to us that being a large object high off the ground was a bad idea during a lightning storm.  The genny (and the trucks etc etc not to mention flown grip frames and large lights up high on stands or even your raised-up wireless antenna array) seem like they'd be attractive targets for a strike?  We were all shoo'ed away from those and told to shelter inside a building...

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"How often does lightning strike" seems like a Google question to me.  I think it's the lightning rod principle.  I started my answer with the idea that electricity takes the shortest path across the highest voltage differential.  Generally, elevated, metallic objects attract lightning strikes, and the idea of a lightning rod is to attract the lightning to the rod where it can be dissipated harmlessly to ground rather than strike something else.

"Elevation" addresses the "shortest path" part because it's closer to the thunderhead than the ground surface, and "metallic" addresses the "voltage differential" part (indirectly) because it provides a lower resistance path to ground than the air.  If I'm not mistaken, lightning rods are sometimes (usually?) given a positive charge to help make them more attractive targets (assuming my memory is correct and thunderheads are full of negative ions).

Applying that to on-set generators, generators would be potential strike targets because they are slightly higher than the surroundings, and some of the internal components may be slightly more positively charged than the surroundings.  If you live in a mountainous region like me, or if you are set up in an urban environment where there's lots of buildings around, presumably the generator isn't a very attractive target, but if you are filming on the open prairie where lightning storms are common, it seems plausible to me that a strike could be more likely.

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Ah!  I thank you for the elaboration and details.  I think that answers my question.  I guess the only safeguard would be... pounding some tall lightning rods next to the gennies!  I mean, lightning delays cost so much and are so damn inconvenient.  I'm super bummed we have to go back there and finish those scene.  Lightning.

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CA/AZ border is no joke when it comes to electrical storms. 
 

I’ve been shocked, but yet to be electrocuted. Finger in a light socket. 
 

Mountains are still no joke. Half Dome had a strike and took out a few hikers at the summit. It really stuck with me because I’d been there. 
 

I know it sucks to get out of the work rhythm. I’m one that would pass on the “run with lions” type stuff. 
 

 

 


 


 

 

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Disclaimer: Not an electrician; do your homework before messing with this stuff or better yet, hire a professional; seriously don’t listen to some random guy on the internet. 

 

 

In power generation the “earth” is the literal return path that the neutral is bonded to. So when you tie a building into the grid, each structure makes the connection back to the ground to complete this path. But with a portable generator the earth is not used as a return because the generator is the source of power and it has no connection to a power generation plant. Instead the neutral and ground lines are bonded together and are grounded to the frame of the genny. This makes the whole generator and anything attached to it a floating system which is totally fine and safe. But in a highly energized atmosphere a lightning strike that may hit the genny or any equipment attached to it has only this self contained system to dissipate the energy through. Eventually it will dissipate into the ground (just because of the huge potential difference between the earth and the atmosphere), but not without going through every single wire, chassis, and person in contact with it first.  So it’s not like a hit will just take the genny out; it takes everything out, and that’s a lot of equipment and people all sharing a physical connection in one isolated network. And just like @documentarysoundguy said, any metallic, elevated, positively charged surface (looking at you aerial antennas) can attract a potential strike, especially in an open air situation. 

 

The whole idea is one of safety and an abundance of caution. It simply isn’t worth the risk. I work primarily as a live sound engineer and any time there is an energetic atmosphere and strikes within a mile of an outdoor event using portable power and an elevated stage, things get shutdown until it’s all clear. Rain is fine; lighting is no bueno.
 

Even indoors isn’t totally immune to an energetic atmosphere. I once had a large, visible, and loud static discharge off of a sub stack into the air. The speakers were sitting on rubber shock pads to keep them from moving around and the constant moving of the speaker cones, that were coupled to the air, generated a sufficient enough potential difference that it arced. Outside was a very beautiful and active lighting storm with no rain. It was the most bizarre thing. 

 

Anyway, all that is to say it’s just a good and safe practice and there isn’t anything particular about the generator other than the entire network being electrically isolated which in and of itself has a higher probability of danger in an electrical storm. 

 

I should also add the caveat that I’m not an expert in this at all and this is just my best understanding of the subject. 

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