JP1 Failed Fence segment question.

Obviously the larger main fences through the park, along with the reinforced perimeter fences, run on an alternating current, so that the can't be shorted. What happens if a large tree or branch blow over, either -leaning dangerously on the fences -taking out a segment of the fences, internal park area fences particularly? -Are they forced to shut off an area? -Are area fences dual supplied from two ends in the enclosure loop, allowing them to shut off one segment only for maintainance (the fallen tree example), or are they stuck turning off the whole area? -Particularly, what happens if one or more segments suffer a critical failure despite everything, in the case when the fences are on?