Skvez (and other interested folk).
Probably teaching you all to suck eggs but it's relevant here.
The individual solar cells are just little diodes, like a LED.
Just backwards. To light a LED you put electricity in, where a PV cell uses light to make electricity.
Each PV cell is fine at MAKING electricity, it just don't like being FED too much electricity the wrong way round.
An EMP pulse or Geo-magnetic strike can do precisely that i.e. force feed something the wrong way round.
Each module in a PV array is usually protected with bypass diodes.
Those have a peak REVERSE voltage rating.
Simple thinking, if one array goes short, the diodes protect the rest of the panels by blowing fuses. These diodes can only take so much though.
Or, in plain speak, "Please don't squirt too much voltage the wrong way into me as the most I can take is":
1. 8A, 45 PIV (Peak Inverse Voltage) for 72 & 96 cell modules.
2. 12A, 200 PIV (Peak Inverse Voltage) for 96 (commercial use),
128 cell modules.
A typical set of figures from
http://www.sunpowercorp.com
Reading Google articles on solar flairs,
http://www.thespacereview.com/article/1549/2 is a good one.
It mentions a 1.5KT nuke frying diesel generator windings by breaking down the insulation resistance.
I used to test 40KVA Houchin diesel generator windings for a living using 1500 volts insulation test "zappers".
If they survived that particular test, the winding was deemed serviceable.
So I'm thinking a 1.5kt nuke must generate more than 1500 volts in one of its three pulses of energy.
Look above and 45 / 200 PIV figures look a bit sick against more than 1500 volts the wrong way round i.e. BANG (but quietly).
The suns flairs are WAY BIGGER than a piddling little 1.5Kt nuke.
Further away admittedly BUT still pack a considerable punch when they hit the earth.
A solar eruption hits in 3 ways (just like a nuke EMP does).
First comes electromagnetic radiation,
Then radiation, and finally the plasma from the sun.
This is the bit that screws up electrical systems.
1989, Canada (Quebec) was brought down by one.
Now if a PV panel gets hit by this 3 stage blast, PV cells or protection diodes may blow.
If the PV cells blow open circuit not a problem, if they blow as a short it's the same effect as dropping a spanner across a car battery (just not so spectacular).
Everything dies as it shorts out it's neighbour, and the next one, etc. A cascade failure.
Adding an earthing strap won't help as all your doing in grounding the casing.
So the only logical (but totally impractical thing to do) is to Faraday cage the panel.
In the long run it's just going to be better to simply unplug any long wires to stop induced voltage from the EMP / Solar flair feeding back into the panel or the controller and hope for the best.
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