An Avionics Mechanic reports on the difficulty reading the wire identification markings in the forward cargo pit ceiling of a B777-200. A hydraulic pump wire bundle had overheated; shorted and arced and damaged the cabin floor beam.

Narrative

Inspected and attempted to make wire ID list of affected wires. Gave list to lead on duty for operations check processing. Secured bundle; sold to inspection. Wires were difficult for me to read. At the time I believed if I read any wires wrong; they would not show on the wire list for processing operations checks.Callback conversation with Reporter revealed the following information: Reporter stated that at least three; heavy gauge electrical wires; for the Center electric hydraulic pump (C-2) had overheated; shorted and arced. The overheated wires became so hot; that a cabin floor beam was damaged and required structural repair. Although the cabin floor beam was repaired and inspected; the required inspections and listings of all affected wires and wire bundles damaged by the shorted C-2 pump wires; had not been accomplished. Many of the wires affected by the shorting and arcing of the C-2 electric pump wires; required environmental splices that had not been listed or identified by the Line station that had previously accomplished the electrical repair work.