What was found
(CAN) ELECTRICAL ARCING AND BLACK BURN MARKS PRODUCED WHEN CONNECTING A MOBILE GROUND POWER UNIT TO ACFT. PASSENGERS WERE DEPLANED. CRASH FIRE RESCUE RESPONDED. NO INJURIES REPORTED. REMOVED AC POWER RECEPTACLE IAW AMM 24-42-03-000-801-A. FOUND COMPOSITE PANEL DAMAGE ON EDGE OF CUTOUT. EDGE PANEL DAMAGE REPAIRED IAW SRM 51-71-01 RE FOR FULL REPLACEMENT OF THE EXT. PWR RECEPTICAL BOX NEXT BSA 01 CHECK IAW PP ERJ190-24-56166. INSTALLED NEW AC POWER RECEPTICAL IAW AMM 24-42-03-400-801-A FUNCTION CHECK CARRIED OUT NO FAULTS. NO ACFT DEFECTS RELATED TO OVERVOLTAGE, OVERCURRENT, AND INTERLOCK. SYSTEM SERVICEABLE.