I still don't understand what happened to the outlet strip...
OK... I'll take a shot at explaining what I think happened... (someone else might be able to offer a better explanation). Fundamentally what has occurred is an arc-fault.
Conventional breakers usually trip before the insulation can be damaged by excessive temperature, and the time of the response is designed to prevent a circuit overload. However, arcs are usually fairly short in duration and breakers cannot detect the fault.
Yes, all RPTs and TVSSs are equipped with circuit breakers (at least all that I've seen). But, because of a bimetal heating effect that happens during an arc-fault, conventional circuit breakers may never trip because the RMS current level associated with the intermittent rise in current could be considerably less than the RMS rating of the breaker.
There are two basic types of arc faults and circuit breakers usually cannot detect either. You can have a high-energy arcing (parallel) or high-resistance (series) faults.
High energy are caused by insulation failures between conductors of different potentials. Once the insulation is compromised, arc heat melts the actual conductors (6000+ degrees C) creating a new path which causes intermittent arcing. A circuit breaker may not trip, because, a magnetic breaker requires a minimum peak current, and a thermal breaker requires a minimum duration of the peak current.
A high resistance arc fault usually happens because a layer of oxide has formed at the conductor connection points. This "corrosion" creates a high resistance path that generates heat. Broken or damaged conductors can also cause this type of arc fault.
This is really the reason why AFCIs have been developed and required by the NEC on some circuits. I didn't take the strip apart to identify the actual cause of the arc fault damage... in my job, I don't have to identify the cause of a hazard, just that the hazard exists. I let one of you (contractors/electrical engineer) figure out the cause and the solution. Talk about passing the buck!
So that you don't think I'm an electrical engineering genius here... I liberally paraphrased this answer from an article on AFCIs in the Feb/Mar 2002 issue of the NEC Digest.
As I said at the beginning, someone else may have a better explanation.
Feel free to take a stab at it...