A few weeks ago, I had to help a friend move his boat (at the East End Yacht Club in Stratford, CT). Adjacent to the club is an oil tank farm-at the end of the tank farm are two tall antenna towers. I thought they were radio transmitter towers, but there were no antennas on them. They obviously are intended to deflect lightning, so as to prevent a fire from a lightning strike.
Do they work?
No; if anything, lightning is more likely to occur in an area with tall conductive objects - the purpose of the towers is to redirect a lightning strike (lightning usually strikes the tallest objects, thus why lightning rods, the proper name for the towers, are used). Yes, they do work but can’t guarantee absolute protection, but in most cases they will divert lightning that strikes (lightning doesn’t always hit the tallest object, and the current is so high and brief that a lightning rod has significant inductance and skin effect losses). A lightning bolt hitting an oil tank is unlikely to cause a fire though since they are metal and oil won’t burn unless mixed with air (spilled oil and/or fumes could ignite however).
NFPA 870 covers electrical safety. DA PAM 385-64 chapter 17 comes directly from there with emphasis on storage facilities and is my bible. I work in ammunition and explosive safety and those are the sources for lightning protection systems. The three main types are lightning rods on the structure itself, masts (the antenna towers you saw), and masts with overhead wires running between them (cantenary system). The important principal is to adequately ground the systems. They will attract the lightning preferentially to them if high enough and cover the entire area to be protected. If sufficient down connectors (number and wire gage) are present AND have a low resistance to the localized earth potential; a strike will be dissapated. Bad grounds or poor design can result in side flashes or direct strokes to the “protected” facility. The rods have to be at least two feet above the adjacent structure. Masts and wire systems use a “rolling ball” with a radius equal to the height of the mast/wire to define the protected area.
With an oil or other volatile tank, a strike might melt a hole in the tank and the heated metal could ignite any vapors present. You’ll see lots of lightning protection measures at a refinery with the multiple cracking towers.
Lightning doesn’t always play by the rules. It’s still not completely understood.