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Old 09-22-2019, 07:42 AM   #1
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LIGHTNING STRIKE protection

Just wonder how many Joules of protection are needed to have no harm from a marina line wire lightning strike?.
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Old 09-22-2019, 11:02 AM   #2
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Just wonder how many Joules of protection are needed to have no harm from a marina line wire lightning strike?.

According to the University of Illinois dept of physics, 1-10 billion joules of energy in a bolt 3 miles long.

https://van.physics.illinois.edu/qa/...ghtning-strike
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Old 09-23-2019, 06:10 AM   #3
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"According to the University of Illinois dept of physics, 1-10 billion joules of energy in a bolt 3 miles long."


Interesting , but I wonder just how many joules will need to be grounded from a house or marina line?
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Old 09-23-2019, 06:39 AM   #4
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Just wonder how many Joules of protection are needed to have no harm from a marina line wire lightning strike?.
All of them.
Seriously even if you ran a welding cable from your boat ground bus to a 8 ft copper ground rod on shore, there is no guarantee that lightning won't follow it into your boat and out your thru hull fittings.
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Old 09-23-2019, 09:48 AM   #5
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One of my current jobs is to design hardened electronics for lightning immunity.
I use some of the more aggressive specs for my tests.
For instance, my surge generator delivers 4kV pulses with a 330Amp maximum level in common mode, and 2kV pulse with 1000Amp in differential mode. These are the kinds of levels measured on actual utility lines during nearby strikes. This is NOT the level if such a strike lands DIRECTLY on your cord.
To pass such a near-strike; it takes maybe $20 or so of raw parts cost.
Note that using a isolation transformer is highly effective in stopping most all common mode surges. This leaves then, the normal mode surges that can be effectively clamped using easily available surge suppressors. Best done in two stages, at the panel and then at the load.

Yes, an actual bolt of lightning contains an overwhelming amount of energy, but unless a direct strike is taken, mitigation is not particularly difficult, for even nearby strikes.

For completeness; there are effective methods to handle direct strikes to buildings with electronics within, but, not to the actual electronics directly. Lots of grounding and copper will be required to divert the energy to somewhere less expensive.
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Old 09-23-2019, 12:49 PM   #6
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We had the electrical systems on half the boats in our marina ruined when a contractor with a back hoe, hit the underground lines and changed 120 volt lines into 240 volt lines.
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