As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE OVERVOLTAGE SENSOR ACTIVATED, CLAMPING THE ACU POWER SUPPLY TO GROUND. THE ALTERNATOR CIRCUIT BREAKER FAILED TO TRIP. THIS RESULTED IN AN INFLIGHT ELECTRICAL FIRE WITH THE HARNESS BETWEEN THE J-BOX AND CIRCUIT BREAKER PANEL DAMAGED AS MULTIPLE CIRCUITS WERE BURNED. AT LEAST THREE OTHER BREAKERS TRIPPED BEFORE THE MAIN BUSS BREAKER LET GO. THE FIRST WIRE BURNING STARTED A CASCADE OF SHORT CIRCUITS.