The foremost important thing is your interest. You can get into fields like research and innovation but it is recommended that you apply for jobs through GATE to get into reseach field. Some of the companies which you refer to are:

BHEL, NTPC, Power Grid Corp, Indian Oil, ONGC, DRDO, ISRO, SAIL, GAIL, TRANSCO, GENCO etc.

You can even study Mtech futher and then go in proper research field.

You can give GRE and apply for abroad studies and jobs which will definitely broaden your scope and career growth.

To get good opputunities you should have a clear understanding of technical knowledge of your subject along with your communication skills.

Good Luck.