AFCIs and lightening

Make sure that there is no significant capacitance between hot and ground. Capacitive current to ground can trip.
Bill -- Ferme le Bush

Thanks Bill:
I'll talk to the electrician about that. I understand capacitance in electronics but where would it come from in an electrical system?
BTW - the electricity going out and the storms almost always occur during the night. At those times I have a Hunter ceiling fan on, it has some kind of solid state circuit. In the rooms where the AFCI does not trip, the fans are always off at that time.
Gus

There is the capacitance just between wires, but that is probably not enough. If there are any surge suppressers around, some of them night add some filtering by connecting capacitors from the line conductors to ground.
I also once had a submersible pump that had leakage from the motor winding to ground. It was not enough to be a hazard if the pump case was properly grounded. When the pump was turned off, there often was enough of an inductive kick to trip. All these leakage currents add together to lower how much additional leakage current is required to cause a trip.
Bill -- Ferme le Bush

Not explicitly stated - AFCIs include ground fault protection and trip at 30 ma. (GFCIs trip at 5 ma.)
A surge suppressor downstream from an AFCI (or GFCI) intercepting a surge from lightning, or other, could cause a trip (shunting the surge to the ground wire). Same for a UPS with built in surge suppression. Another possible is current to ground through circuit capacitance resulting from fast rise time on a lightning induced surge.
[Do AFCIs and GFCIs trip on very short ground faults?]
Sounds like the trip could be from the Hunter fan. You could try running the fan in the other bedroom(s) when you anticipate a storm to see if that AFCI trips with the fan on.
If caused by lightning induced surges a service panel surge suppressor may help (is a good idea anyway).
Replacing the wire from the pannel to bedroom would only help if there is a problem with the wire - seems remote. Unless the electrician sees some other problem.
bud--

Thanks for the note Bud. >
I have a GFCI on an expernal house circuit that was intended to run to a well. I have it running to an automatic gate, only thing on the circuit. It has been found tripped after electrical storms before.
There has been a power strip in the master bedroom circuit for he tv and vcr. And of course, the Hunter fan that was on, and an alarm clock.
The other AFCI breaker protects the other two bedrooms. One room is my computer room that has two UPSs. This AFCI has never tripped before, before the incident last weekend when both the AFCIs tripped. This is a 52" ceiling mounted fan. I can leave the other two Hunter fans on in the other bedrooms and the one off in the Master bedroom. Switching out the 52" would be a lot of work. Now that's an idea the electrical company did not come up with. A panel surge suppressor can't cost more than rewiring the bedrooms.
Hey, these "electricians" are who knows what, working under someone's license. They don't see anything. They had to come back and tighten all of the wall switches and outlets because a finisher did not tighten the screws on the devices.
This is a new house that I babysat while it was being built. I saw nothing in the wiring that was suspicious and thought they did a great job.
Thanks for the suggestions I'll take to the contractor.