You have to score above 30 to get a secured position. Cutoff is in the basis of category. so it depends to which category you belong to. for general category the cutoff for 2019 year was :- 28.7. On the basis of rank you have to secure a rank below 500 to get an admission at IIT. so for PSU you have to score near to it. So your score need to be near 100 marks for a secured Position at PSU.
Hope it helps!