Ramp Agent reported a failure in the external power connector when ground power was applied to the aircraft. A loud popping noise was accompanied by smoke and sparks. The ground power was disconnected and the external power cable was placarded INOP.

Narrative

Aircraft X from ZZZZ blocked into Gate X at XA:39 in ZZZ. Lead ramp agent plugged in the ground power as normal and turned it on. Upon pressing the button; the GPU panel immediately made a popping noise and smoke and sparks were visible coming out. The lead ramp agent immediately shut off the power and call the Supervisor to the Gate. Upon asking the Captain if anything was wrong with the ground power panel; they simply stated that some sort of small fire issue in ZZZZ and that the GPU outlet was deferred. After closer inspection; there was one INOP sticker positioned in such a way it was not immediately visible inside the ground power panel. But with a risk of electrical fire; I do not believe a small 1 inch INOP sticker is sufficient in warning of the potential shock/fire hazard. Lead ramp agent says no burn evidence on the panel or receptacle upon arrival. Further; no communication was made between Company Maintenance/Flight Crew/ZZZZ to any ramp personnel; Managers; Supervisors; etc. about the hazard. A completely avoidable situation with some simple communication. Please see attachment pictures for aftermath. Of note are the additional stickers Company. Maintenance added after the fact; and the on.