Our electric company took down the chainlink fencing and put up 10 ft brick walls around all the small stations. Expensive project for less security. At least with chainlink, anyone inside would be seen. With the new easily scaled walls, there’s no way to see if anyone is inside.
Most substations are both isolated and unmanned, so there is no one there to "see" anyone inside anyway. Motion-sensor triggered cameras linked back to "headquarters" fix the "problem". And those should be there whether there is an opaque fence or not (think "kids").