A fence answers the wrong question
Chain-link handles someone wandering in. It does nothing for a thermal event, gives responders no room to work, and will not stop a round reaching an energized cell. Call it the security measure and every consequential risk on the site is still sitting there, untouched.
Design the perimeter to the consequence
Start from what the site is worth to the grid, how long a replacement would take, and how far a cascade could spread. That number sets your standoff distance, your responder access, and whether the energized enclosures need genuine ballistic protection rather than a line on a survey.
Where the consequence justifies it, specify ballistic protection rated to a defined threat.