Forgive my denseness, I'm trying to understand this in lay fashion.:

They were increasing power in the affected section.

At a certain point in the power increase, resistance developed due to a badly soldered connection?

The resistance was detected and safety systems attempted to reduce power but for some reason an arc occured?(I really don't understand this part but my knowledge of electricity is essentially nil)

The arc punctured a line/vessel containing liquid helium allowing it to boil off into areas of vacuum?

The liquid helium boiled off/expanded so violently that it moved/shifted/caused physical damage to large structures in proximity of the arc, in spite of safety valves trying to reduce the pressure?

The flowing helium carried soot and debris from the arc into neighboring areas of the LHC?

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