We are trying to build a small patio along the end of our yard (along the fence), but there is a small power line that runs through all the houses in our side. Is it safe to build a patio along the fence which is closer to the power line? (the power line is in our neighbor's yard)
It's safe. The power company is very careful that no one gets hurt.
What you need to be concerned about are utility easements.
Check with the power company especially if you want to plant a tree.
They need to be able to get in and trim trees and you are not allowed to let your project get in the way of trimming the trees.
Other than that, you are safe. I'm an electrical engineer and have had issues with the power company and access to the trees they needed to trim.