What was found
03AUG21 MEM OVER NORTH ATLANTIC, ELEC GEN OFF R, STARTED THE APU WITH APU GEN OFF, RESET GEN PER ECL. . APPROX 2.5 LATER, GOT ELEC AC BUS R. RESE THE R BUS TIE PER ECL, RESULTING IN SINGLE GEN OPS. CONF CALL WITH GOC, MOCC AND TECH PILOT AGAIN, USED CAPT EMERGENCY AUTHORITY TO RESET THE R GEN A SECOND TIME (RESET PREVIOUSLY AFTER ENG START). R GEN RESET OKAY. UPON LDG, ELEC GEN OFF R AGAIN WITH MULTI ALTS AND STATUS MSG WITH L AND R BUS TIES IN ISLN. FACT 03AUG21 07:41 MEM INITIAL EVAL CFMD L AND R BUS TIES ISO W/ LOAD SHED OF VARIOUS SYS'. M/MSG: 24-28860 LOGGED INTMT LAST FLT-LEG (BPCU HAS NO OUTPUT ON SYS ARINC 629 BUS RIGHT). T/S REF B777 FIM: 24-41 TASK 816, CYCLED L AND R BUS TIE RELAYS AND RE-GAINED NML AC SYS PWR SUPPLY. ATTEMP TO ACCOMP CH 24 BPCU LRU SYS GND TEST(S) UNSCFL FULLY W/ TEST IND INHBTW/ ALL PREREQ MET. VRFD BPCU OPS SOFTWARE CONFIG EFCT PER ADSM SITE W/ P/N: 2405-SUU-BCU-04 INSTALLED. CYC ASSOC C/B'S, REF B777 AMM: 20-60-05-2 W/ NO HELP. UPON R&R BPCU AGAIN, REF B777 AMM: 24-41-05-4 AND RE-VERIFIED OPS EFFECTIVITY W/ ALL ASSOC TESTS PASS. ALL GEN'S CAME ONLINE NML W/ NO FAULTS; RE-DIST PWR SOURCES AND LOADS W/ NO FAULTS. SUSPECT PREV REP BPCU HAD A FAULTY CHNL OR CHNL GOING BAD, ONLY RVLD AFTER CPL FLT-LEGS. A/C OK FOR SVC.