Hello dear, 

Thanks for contacting us. 

The age criteria varries from PSU to PSU. Some psu like iprcl states that the candidate must not exceed 32 years and psu like AAI states that the candidate must be under 27 only. So i would suggest you to visit the link provided below for more information: 

Https://engineering.careers360.com/articles/psu-recruitment-through-gate

All the best!

Hey verma,

The age criteria varies PSU to PSU like there are some PSU like IPRCL  as for that , the candidate should not exceed 32 years and for PSU like AAI age should be under 27 only. So I would suggest you to go through the below provided article to know the age criteria and other important information, also you can apply for some of them as they have released the application forms as well -
PSU Recruitment through GATE 2018

dear student

Most of the PSU Companies age limit varies from 25 to 28 and somewhere 30 years. For example for HPCL, BPCL, it is 25; for IOCL it is 26 years;for NTPC it is 27; for Power Grid it is 28; for ONGC it is 28 for drilling and cementing (and for all other posts it is 30).

You have to visit individual PSU advertisement fulfilling criteria.

hope it helps

All the best!!!