The fence is a tile that is present on all prisons and can be cut with a File File or any form of cutters (Flimsy Cutters, Lightweight Cutters, Sturdy Cutters). The electric fence, however, features a blueish color and is buried partially underground, obstructing . It is noticeably thicker than the normal fence, and upon attempting to cut through it, it shocks you and inflicts 10 damage, provided the Generator on the map is running. 

You will be sent to solitary if the guards notice a cut fence; to avoid this, you can use a Fake Fence in place of the removed one.