What are the VFD's installed in?
If you are using non-metallic cabinets then this is one point that could be addressed, along with what type of wiring method are you using PVC or RMC, look into flat braided wire instead of regular round wire for your GEC conductors, and keep any GEC's away from the motor and control wiring, the idea is to not invite the lightning to the inside of your control cabinets by doing all your GEC bonding outside of it, and only having one bond point (single point bonding) if you have multiple ground rods, don't bond one to one side of the cabinet then bond another to the other side as this invite the lightning current to travel across the cabinet, bond from ground rod to ground rod or take them to the single point bond, which should be a copper plate drilled and tapped, some supply houses have them or can get them, burndy makes a few styles then take it to the single point bonding point also bring your well bond to this single point.
Without knowing much about the system you have, it's hard to offer much else but one other point is to avoid as much as possible in routing wiring in loops, like if your motor leads take one path to the well then you have control wiring going to another point lets say point 1 try to avoid running another set of conductors from point 1 to the well as this will create a loop that a near field lightning event can induce current into, try to run conductors more like spider legs where you run to one point then out to the different points, PVC even buried underground can have a lightning EMP induced into it, so the more you put into a metallic raceway the less lightning can affect it. also use some TVSS devices where possible, you can get MOV's rated at almost any voltage but care should be taken when using them on very low current circuits such as PID's and other I/O's as they can load down the circuit and cause problems, but installing a good surge protectors on the supply and any control power supply's or transformers can limit some of the surges that come into the system from the utility or internally generated from inductive sources like relay coils, solenoids and such.
Just remember lightning is a very high energy event, it has a very high current and voltage, and is also a high frequency event that many do not understand that can induce current into wiring just like a transformer induces current from the primary windings to the secondary windings, also just like a transformer this induced current is no longer seeking a path to Earth, all its trying to do is to complete a circuit this is why you try to not form loops in your wiring, as when you only have one pathway current can not flow as it will treat all the conductors in a pathway as only one conductor and we know current can't flow if there is no other path, here is some good examples of loops that is common to receive damage in a near field strike ( A lightning strike to a tree some where about 20' to 100' from the building or equipment) a phone that is plugged in to a receptacle outlet that also has a phone wire connected to it, you have one path through the 120 volt circuit from the panel run in one path through the attic, then the phone cable run in another path which the phone company also bonds at the service, this creates the loop, and is almost impossible to avoid. others is networks, TV's with cable to them, and even entertainment systems that might have a sub woofer located across the room plugged into an outlet fed from a different circuit, all these have one or more different paths through a home that come together at both ends forming a loop, and since this induced current treats all the conductors in a cable as one conductor, TVSS devices can do little to stop this kind of damage which will happen to the weaker electronics that are between or in series with this loop.
Damage can be minimized but never totally eliminated, so even with all the protection you can muster you can still get damage.
Class dismissed
