▁available ▁to ▁Unit   1 ▁from ▁off - site ▁sources . ▁However , ▁the ▁Vog t le ▁elect rical ▁system ▁was ▁not ▁designed ▁to ▁permit ▁easy ▁inter connection ▁of ▁the ▁Unit   1 ▁vital ▁b uss es ▁to ▁non - v ital ▁power ▁or ▁the ▁Unit   2 ▁elect rical ▁b uss es . ▁Since ▁this ▁incident , ▁Plant ▁Vog t le ▁has ▁implemented ▁changes ▁to ▁the ▁plant ▁that ▁allow ▁the ▁non - v ital ▁elect rical ▁bus es ▁to ▁transfer ▁power ▁to ▁the ▁vital ▁bus es ▁in ▁this ▁type ▁of ▁scenario . ▁ ▁This ▁elect rical ▁fault ▁also ▁affected ▁Unit   2 ▁by ▁causing ▁break ers ▁in ▁the ▁ 2 3 0 k V ▁switch yard ▁to ▁trip , ▁cutting ▁off ▁power ▁to ▁R AT ▁ 2 - B ▁and ▁vital ▁bus ▁" B ." ▁ED G ▁ 2 - B ▁subsequently ▁started ▁and ▁restored ▁power ▁to ▁the ▁vital ▁bus . ▁At ▁the ▁same ▁time , ▁the ▁elect rical ▁disturb ance ▁from ▁the ▁falling ▁line ▁striking ▁the ▁ground ▁was ▁detected ▁by ▁protect ive ▁saf eties ▁on ▁the ▁Unit   2 ▁main ▁step - up ▁transform er ▁and ▁a ▁protect ive ▁relay ▁actu ated , ▁opening ▁the ▁transform er ' s ▁output ▁break er . ▁This ▁caused ▁a ▁full ▁load ▁re jection ▁to ▁Unit   2 , ▁leading ▁to ▁a ▁tur bine ▁trip ▁and ▁subsequently , ▁a ▁re actor ▁sc ram . ▁After ▁Unit   2 ▁tri pped , ▁the ▁" B " ▁non - v ital ▁elect rical ▁train ▁lost ▁power ▁as