Many offshore platforms are "fixed" to the earth by use of pilings driven to refusal and then welded to the topside structure. We typically ground every electrical devise to structure steel. I have 42 years experience in this field mainly in the GOM. My company is being asked to provide either lightning arrays for critical areas which "eliminate" the lightning strike. Or, going to lighting protection at each critical circuit. Their are thousands of critical circuits, and their are many platforms operating that do not have either of these systems installed. What do the experts say about effective lightning protection of a structure that is "pinned to the earth" in seawater? Any help would certainly be appreciated.
Hi David: I'm across the Gulf from you in the lightning capital of the country - Ft Myers on the edge of the Everglades. We know lots about lighting.
There are line side strikes & there are load side strikes.
You can do an array of copper spikes.
You can do line side clamping.
You can do load side clamping.
There are some really heavy duty MOV's on the market and they're very cheap. If the majority of your critical devices are instruments & computers, your solutions could be this easy. For our 3-phase protection at our plant, we paid around $800 each for the equipment. If you give your BOM to a factory applications engineer at any of these companies, they can price out the equipment quick.
Whatever system(s) you come up with, it will need periodic maintenance. The spikes blow off and the MOV's expand and are less effective on subsequent strikes.
Assuming you're in international waters, what standards do you use? NFPA 70? Are you restricted to Listed assemblies? Seems you could wire a MOV into a circuit really easy (read that cheaply) if you can get away with it. Not sure what the EC's & Inspectors on here would say about that though.