You can contain hogs with 1 strand of hot wire placed about 6 inches above the ground but they need to be trained to electric fence before you turn them out.   

We farrowed sows for many years on pasture with electric fence keeping them in.  If you've got a good fencer that the sows respect the power can be off for quite a while before they'll bother it.

Do as the others have suggested and put a hot wire inside their pen, fence off a corner or something so that they learn to approach it slow.

It also helps to keep the ground under the fence wire bare so that there is a noticable dead strip so that it is easy for them to see.