Powerline Glade comes off from the top of the Mountaintop Express (Chair 4) Lift and you take the first left on the traverse over to Ramshorn.
Then at any point take a right into the tree glades and you will hit Powerline Glade.
There are usually moguls at the top with fairly open glades and then the bottom pitch is much steeper and more difficult.
It ends pretty quickly though and you're back at the bottom of the Mid-Vail area.
The Chair 4 cliffs are right under the lift, also known as "Hollywood" since everyone will be watching.