First of all congratulations on clearing jee mains exam.

You got 78 percentile in jee mains and willing to get ece or elctrical branch in nit or iiit as you are in sc category. So don't you worry, you've secured your seat in nit or iiit. You can easily get ece or electrical branch in nit or iiit but try with lower rank nits or iiits. Because your percentile is not good enough to secure seat in best nits or iiits. So choose wisely for the college in JOSSA and if you want accurate result where you can get the seat in colleges and know your exact status go through this link, https://engineering.careers360.com/jee-main-college-predictor?icn=QnA&ici=qna_answer