Can I suggest you go to a different shelter? There is no way that an electric fence is better for dogs who escape frequently than an actual fence.
What you need to do is get an actual, tall, fence and maintain it. They sell hardware that you hammer into the ground to help prevent the dog from escaping - dig defender is the big brand name I think.
The electric fence is the “easy” way out that doesn’t actually solve the issue. My parents neighbor has an electric fence and quite frequently their neighbors dog ends up in their yard when he shouldn’t have been stopped by the fence. He’s a great dog and my parents enjoy him but still.
If you want to prevent the dog from escaping, you need to take the responsibility of the fence and maintaining it.