Narrative:

[At] approximately 96 knots; first officer and I both identified EICAS alert; elec AC bus right; takeoff was continued and announced as such as per SOP; normal rotation; no issues. During climb out; power setting reverted to con; FMC displayed eo speed of 258; and a maximum altitude of 247. Jet obviously thought it was in some kind of engine failure status and responded accordingly. First officer's efb dumped as well and went black. Later a restart and time for it to do so returned it to normal status. All engine was selected on 5R of VNAV climb page; climb was selected on perf page and climb out continued. I kept the aircraft and the radios. First officer and relief first officer ran non-normal checklist. First and only non-normal checklist to populate was elec gen off right; with a status message of elec gen system right displayed. We accomplished the one reset of the right generator control switch allowed; but it did nothing. APU was started and remained running until block in at ZZZZ with primary/secondary external power selected. Non-normal checklist was completed; after takeoff was completed; and then I called dispatch for a 3-way phone patch with maintenance control. [Individual] in dispatch and [individual] in maintenance control picked up and I explained the issues we had. [Maintenance control] said the ahm populated a low voltage in the right engine idg. [Dispatch] sent new fuel numbers; as it requires a 2.5% over burn per APU door open. We took off with 185;000 lbs. Of fuel of which 40;192 was for tanker. Obviously; fuel status enroute or upon landing was not a concern. Finally; I made a call to the duty officer to give [him] a synopsis of what had transpired even though fom doesn't require this call. I didn't know how well dispatch and maintenance control had alerted down line support and knowing this would take 3 hours to replace the idg; [he] could follow up to insure ZZZZ maintenance was prepared for a quick repair.

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Original NASA ASRS Text

Title: B777 Captain reported multiple failures associated with low voltage on the right engine IDG.

Narrative: [At] approximately 96 knots; FO and I both identified EICAS alert; ELEC AC BUS R; takeoff was CONTINUED and announced as such as per SOP; normal rotation; no issues. During climb out; power setting reverted to CON; FMC displayed EO SPD of 258; and a MAX ALT of 247. Jet obviously thought it was in some kind of engine failure status and responded accordingly. FO's EFB dumped as well and went black. Later a restart and time for it to do so returned it to normal status. ALL ENG was selected on 5R of VNAV climb page; CLB was selected on PERF page and climb out continued. I kept the aircraft and the radios. FO and Relief FO ran non-normal checklist. First and only non-normal checklist to populate was ELEC GEN OFF R; with a Status message of ELEC GEN SYS R displayed. We accomplished the one reset of the right generator control switch allowed; but it did nothing. APU was started and remained running until block in at ZZZZ with primary/secondary external power selected. Non-normal checklist was completed; after takeoff was completed; and then I called Dispatch for a 3-way phone patch with Maintenance Control. [Individual] in Dispatch and [individual] in Maintenance Control picked up and I explained the issues we had. [Maintenance Control] said the AHM populated a low voltage in the right engine IDG. [Dispatch] sent new fuel numbers; as it requires a 2.5% over burn per APU door open. We took off with 185;000 lbs. of fuel of which 40;192 was for tanker. Obviously; fuel status enroute or upon landing was not a concern. Finally; I made a call to the Duty Officer to give [him] a synopsis of what had transpired even though FOM doesn't require this call. I didn't know how well Dispatch and Maintenance Control had alerted down line support and knowing this would take 3 hours to replace the IDG; [he] could follow up to insure ZZZZ maintenance was prepared for a quick repair.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.