Hello Raja, 
For NET exams, they need you to have a OBC-NCL certificate or be listed under the OBC category at NCBC. You can apply as an OBC candidate only if your name is on the central list of other backward classes available on National Commission for Backward Classes  ( NCBC ). It's a government of India website that you can visit at ncbc.nic.in . State list OBC candidates whose names are not under OBC-NCL cannot apply as OBC and will have to apply under general category. You can opt for a OBC-NCL certificate right now if you want.
There is no information mentioned specific to SEBC certificate, all that is mentioned is that they accept only OBC-NCL certificates for OBC candidates. 
Hope this helps :)