Hello Biplab, first of all congratulations on your GATE score. As you are seeking to get admission into IITs with your GATE score, let me tell you that you can assess your possibility of getting into one by checking the previous year's closing cut offs.
With that score in the SC category and Electrical engineering department, you can most probably get admission into IIT Bombay, and IIT Gandhinagar according to 2016 cut offs.
The 2016 last cut off for electrical engineering in  various IITs is as follows:
• IIT Bombay- 340
• IIT BHU- 505
• IISc Bangalore- 683
• IIT Gandhinagar- 426
• IIT Delhi- 500, 555, 540, and 625 (depending upon different M.Tech programme)
• IIT Kanpur- 416 (signal processing Communication & network) and 397 ( RF, Microwaves and Photonics)
• IIT Patna- 18.72 qualifying marks
• IIT Roorkee- 39.02 qualifying marks.
• IIT Indore- 326 (Metallurgy Engineering & Materials Science)
• IIT Jodhpur- 10000 rank

According to IIT Madras' GATE cut-off you can get admission to one of its M.Tech courses in electrical engineering- Microelectronics and Photonics.
In categorywise, 2017 GATE cut-off for Electrical engineering specialisation was 439 for SC category.
To know more about cut offs in electrical engineering, visit: https://engineering.careers360.com/articles/gate-cutoff-for-ee

Also to predict which college you can get, check this GATE college predictor:
http://bit.ly/2J9S0MN

All the best!
I hope this helps.