They say you can exclude the vast majority of raccoons with 2 electric wires, one at about 4-6" and one at about 12". You would have to make sure the lowest one wasn't shorted out by vegetation or sag, of course.
There are a couple things to know about electric fencing:
1) It only works when the animal contacts both the wire and the ground at the same time, in such a way that the electric charge from the wire gets conducted to the ground thru the animal's body. Putting a wire atop a wooden fence would be unlikely to zap an animal that was climbing the fence (as opposed to standing with hind feet on ground), because wood is a relatively poor conductor.
2) Your charger needs a good solid ground, such as a 6' length of galvanized pipe driven deeply into the soil. The ground rod can't be anywhere near underground metal waterlines, buried utility lines, or utility ground rods - otherwise, you can mess up radio or tv reception, and in some cases risk a dangerously high shock on the fence.
3) Although the charge needed to discourage animals isn't likely to hurt a healthy adult brushing against the fence with, say, their hand, electric fences HAVE caused deaths if they're constructed so that a person can fall on or against the fence or if a child contacts the fence headfirst. Consequently, very low wires such as are usually used to keep coons out of gardens DO fall into the "somewhat more dangerous" category. This isn't a problem if you are an agile adult with no kids around, but if you have any problem that might cause you to slip and fall against the fence, or if you have kids crawling around your yard, you might think twice.
The electric fence should not hurt your chickens as long as they cannot get stuck in it (getting one zap is ok, getting zapped repeatedly is no good for man nor beast).
Hope this helps,
Pat