As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB, LEFT AC BUS CIRCUIT BREAKER POPPED. CREW RESET ALL THREE BREAKERS AND ONE POPPED AGAIN FIVE MINUTES LATER. POWER COULD NOT BE RESTORED TO LEFT AC BUS. FLIGHT RETURNED TO DTW AND LANDED WITHOUT INCIDENT. MAINTENANCE FOUND LEFT AC BUS B-PHASE CIRCUIT BREAKER DAMAGED. REPLACED CIRCUIT BREAKER AND OPERATIONAL CHECK NORMAL ON ALL SYSTEMS DURING POWER CHECK.