Well, I’m back, not that anyone missed me. Had to bug out in a hurry when we found out the the floodwaters weren’t going to crest anywhere near where the Corps of Engineers predicted.
Anyway, made it to my mom’s house. Her basement filled with water and the electric panel was completely submerged, but didn’t short out or trip off. Anyone care to offer an opinion as to why? It was approved on installation by a certified electrician, so I think it is wired right.
Pure water isn’t actually a very good conductor. You can throw a pint of tap water over a laptop and most times nothing adverse will happen. (No promises. 
)
It’s when there’s an electrolyte that there’s a problem. This can be as simple as the sugar in your tea or coffee. It makes the passage of electricity much much easier.
(Another possible answer to your question is that the local power supply was cut first)
Well, the local supply was on because we had lights, etc the whole time. It was very muddy water with an oily smell and sheen. It’s a mess!
Re-reading your post…by ‘trip’, I presume you mean the circuit breaker system? Because that only has any function if there’s a difference between the power in and the power out (ie there’s power leaking to earth somewhere). It’s capable of tripping more quickly and more sensitivily than fuses. But it only detects earth-routed anomalies.
It’s possible that the water didn’t have problematic conductive properties, and allowing it to recede was all that was necessary.
The conductivity of fresh water is likely what precluded a trip of the main or a branch breaker. I was going to link you to an article from the NEC Digest, but the site isn’t cooperating.
Floodwater contains various and sundry hazardous materials and particulate matter such as silt. The electrical properties of a circuit breaker may be compromised by these contaminants, as well as possible mechanical interference in the trip mechanism.
An electrical inspection is a must do, and if it was my home, I’d replace all branch breakers and the main.
That’s the short read of the article I mentioned.
The particulate matter in the water makes sense.
It’s one of those phenomenons, like putting out a road flare in a coffee can filled with diesel fuel. Just put it in the catagory of stuff you’d think would happen but won’t. Although I would definately get an inspection.
Thanks for the information and advice. I will see that an inspection is completed.
semi-related topic … what if the box hadn’t got wet, but some of the wiring below it (think near-floor electrical outlets). Get those inspected, too?