A B777-200 CAPTAIN REPORTS THE LEFT GENERATOR (IDG) HAD TRIPPED. LEFT ENG VIBRATION NOTED IN CABIN. ACFT DIVERTED. ENG HAD SUFFERED INTERNAL DAMAGE; REQUIRING ENGINE CHANGE. MAINT HISTORY SHOWED AN ELMS SYSTEM PROBLEM ON THE PREVIOUS FLIGHT.

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APPROX 2 HRS INTO THE FLT; WE GOT AN EICAS MESSAGE THAT THE L GENERATOR HAD TRIPPED. WE RAN THE ENGINEERING CHKLIST AND WAS UNABLE TO RECOVER THE GENERATOR. PER THE CHKLIST; WE STARTED THE APU TO RECOVER THE LOST PWR TO THE ACFT. AFTER COMPLETION OF THE CHKLIST; WE CONTACTED DISPATCH TO DISCUSS THE GENERATOR FAILURE AND THE FUEL CONSIDERATIONS WITH RUNNING THE APU FOR THE REMAINDER OF THE FLT. WE RANG UP DISPATCH ON THE SATPHONE AND HAD THEM GET MAINT CTL ON THE LINE. I WAS CONCERNED ABOUT OTHER ELECTRICAL COMPONENT FAILURES BECAUSE THE MAINT HISTORY HAD SHOWN A PROB WITH THE ELMS SYS ON THE PREVIOUS FLT. WE HAD NO INDICATIONS OTHER THAN THE GENERATOR FAILURE AND MAINT CTL SHOWED NO ADDITIONAL DOWNLOADED INFO ON THE ACFT MAINT HISTORY SYS. WITH THAT IN MIND; WE HAD DISPATCH WORK UP FUEL BURN NUMBERS FOR THE ENTIRE FLT WITH THE APU RUNNING. MAINT CTL IN TURN FORWARDED THE MEL CARD FOR DISPATCHING WITH THE GENERATOR INOP TO THE ACFT PRINTER. I SUGGESTED TO DISPATCH THAT WE CRUISE AT ECONOMY SPDS WITH A COST INDEX OF ZERO TO CONSERVE THE MOST FUEL. THE ECONOMY FUEL BURN NUMBERS ALLOWED US TO ARRIVE INTO ZZZZ WITH A COMFORTABLE AMOUNT OF FUEL AND WELL WITHIN OUR SCHEDULED ARR TIME. SINCE THERE WERE NO MAINT CONSIDERATIONS WITH THE GENERATOR INOP AND SINCE OUR ARR FUEL WAS ADEQUATE; WE ALL AGREED IT WAS SAFE TO CONTINUE TO OUR DEST. WE ALSO KEPT IT IN THE BACK OF OUR MINDS THAT IF WE DID NOT HAVE ADEQUATE FUEL AT OUR RE-DISPATCH POINT WE WOULD LAND AND REFUEL BEFORE CONTINUING ON TO ZZZZ. WHILE WORKING THE GENERATOR PROB WE GOT A CALL FROM THE FLT ATTENDANTS COMPLAINING ABOUT THE LOSS OF GALLEY PWR. I EXPLAINED THAT THE PWR INTERRUPTION WAS DUE TO THE LOSS OF THE GENERATOR AND THAT IT WOULD BE RESTORED SHORTLY. ALONG WITH THE LOSS OF GALLEY PWR THE FLT ATTENDANT TOLD ME THAT THERE WAS A VIBRATION IN AND AROUND THE BUSINESS CLASS AREA OF THE ACFT WITH THE WORST OF IT BEHIND THE BUSINESS CLASS GALLEY. WE HAD NO INDICATION OF A PROB IN THE COCKPIT; BUT THERE WAS A FAINT VIBRATION IN THE COCKPIT FLOOR. THE RELIEF PLTS WERE ABOUT TO RETURN FROM THEIR REST BREAK; SO I HAD THEM WALK THROUGH THE ACFT AND SEE IF THEY COULD PINPOINT THE VIBRATION. THE VIBRATION WAS PRONOUNCED BUT NOT EXCESSIVE AND IT SEEMED TO BE COMING FROM THE WING BOX AREA. AS I WENT ON BREAK I HAD THE RELIEF PLTS TURN OFF THE RECIRCULATION FANS TO SEE IF THE VIBRATION WAS SOMEHOW RELATED TO THE AIR CONDITIONING SYS. THE RECIRCULATIONS HAD NO EFFECT ON THE VIBRATION; SO I SUGGESTED IT MIGHT BE RELATED TO THE GENERATOR FAILURE ON THE L ENG. I THEN INSTRUCTED THE RELIEF PLTS TO CALL DISPATCH AND GET A PHONE PATCH WITH MAINT CTL TO DISCUSS DISCONNECTING THE IDG FOR THE L GENERATOR. DISPATCH AND MAINT CTL THOUGHT IT WAS A GOOD IDEA; SO WHILE I STOOD BY DOOR 2L ON THE INTERPHONE; THEY DISCONNECTED THE L IDG. UNFORTUNATELY; IT HAD NO EFFECT ON THE VIBRATION. I SUGGESTED THEY CONTINUE TO WORK WITH MAINT CTL TO SEE IF HE HAD ANY ADDITIONAL THOUGHTS AS TO WHERE THE VIBRATION MIGHT BE COMING FROM AND TO KEEP ME ABREAST OF ANY DEVELOPMENTS. MAINT CTL REVIEWED THE ACFT MAINT HISTORY AND DISCOVERED 2 SNAPSHOTS OF ENG PARAMETERS; ONE TAKEN DURING TKOF AND THE OTHER DURING CRUISE FLT. THE ONE DURING TKOF WAS NORMAL; BUT THE CRUISE SNAPSHOT SHOWED EXCESSIVE VIBRATION IN THE FAN STAGE AND N1 ROTOR. AFTER MUCH DELIBERATION BTWN MAINT CTL; DISPATCH; AND THE RELIEF PLTS; A DECISION HAD TO BE MADE AS TO WHETHER WE SHOULD CONTINUE AND JUST MONITOR THE ENG OR DIVERT. I WAS STILL ON BREAK AT THIS TIME SO THE RELIEF PLTS SUMMONED ME BACK TO THE COCKPIT TO HELP MAKE A DECISION. I WAS INFORMED BY MAINT CTL THAT WITH THE EXCESSIVE VIBRATION; COMPONENTS COULD START TO FAIL ON THE ENG. AT THIS POINT IN TIME; WE WERE OVER FOREIGN AIRSPACE WITH OVER 8 HRS LEFT IN THE FLT AND OUR ROUTING HAD US TRAVELING OVER MORE FOREIGN AIRSPACE. WE ALL AGREED THAT THE SAFEST COURSE OF ACTION WAS TO DIVERT THE ACFT TO ZZZ; WHERE WE COULD HAVE THE ENG PROPERLY INSPECTED. DISPATCH; MAINT CTL; THE FLT OPS DUTY MGR; AND CREW SAW NO ISSUES IN MAKING AN OVERWT LNDG. THE WX WAS VFR AND THE LNDG PERFORMANCE NUMBERS SHOWED PLENTY OF MARGIN; SO WE PLANNED FOR AN OVERWT LNDG AT 25000 LBS OVER MAX AT 485.0 K. WE INFORMED THE PAX OF THE SITUATION AND BRIEFED THE FLT ATTENDANTS ABOUT THE OVERWT LNDG AND ISSUED A CABIN ADVISORY TO THEM. THE REMAINDER OF THE FLT WAS UNEVENTFUL WITH THE CONCLUSION OF A SMOOTH LNDG. UPON INSPECTION; THE ENG WAS DETERMINED TO HAVE SUFFERED INTERNAL DAMAGE. THE ACFT WAS THEN TAKEN OTS AND SCHEDULED FOR AN ENG CHANGE.