Montana has areas with severe bear problems, both black and grizzly.  One beekeeper has over 90 fenced yards.  Our seasons result in grass growing through mats on ground, then drying off, so that the bear can walk over the grid like on a carpet.  Our FW&P spent couples years working on bear fences.  BEST by far, even trapped a grizzly and the bear couldn't get out.

Change the concept around - I've videos we embed in our bee classes.   Go to farm supply, buy galvanized ranch panels - they're welded rod, usually 16' long about 4' high.  They sell ones for sheep, cattle, etc.  The only difference, size of the rectangles - sheep ones have smaller spacing on bottom then cattle.

If it's not too big an apiary, you may be able to just hog ring/wire together in a square.   Now, at some point, drive a grounding rod into the ground and run a grounding wire to one of the ranch panels.  Instead of the ground being a mesh on the dirt, the fence becomes the ground.  If you're really paranoid, or for large yard, drive another grounding rod into the ground on the opposite side - but one should do.  Just be sure all of the panels are connected so the whole fence becomes the ground.

Now, buy some plastic stand-offs, clamp to ranch panel facing outward, and run the wires from the charger through the standoffs. 

Bear approaches fence, will either try to push nose through wires or stand to climb over fence.  Soon as any part of bear's body touch ranch panel, it's certain another part of the body will be touching one or more of the parallel, horizontal hot wires.  Absolutely no doubt about ground, and bear gets big zap.

Here in MT, we use 'weed'wacker' chargers.  Again, our problem is mats of dry vegetation and dry soil in late summer, when honey crop is on hives.  Leathery paw pads, dense hairy coat, you've got to get contact with the bear.

And Peter, we've bears that will beat down whimpy or poorly grounded electric fence systems.

Now to the Griz.  FW&P worked with our beekeepers in developing and testing these fences.  They'd throw road kill deer inside to see if bears were kept out.  Final design did this just fine.  Few years later, train carrying wheat derailed near Glacier.  The clean up crew bull-dozed the wheat into a pile, then encircled the pile with one of these fences until the truck and loader could come in and remove the grain.  The pile was at the base of a cut in a hill.  Smart Griz ambled up hill,, took a running jump, and landed on the pile inside the fence.  Had a great feed, but then couldn't get out without getting zapped.  Truck crew showed up to find one well-fed but angry Griz.

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