Fence chargers made with ignition coils are easily shorted out by intent or by weeds. A metal rod lightly stuck in the ground and then touched to the fence will short them out. The secondary resistance of ignition coils may be as high as 10k ohms. A low impedance commercial 12 volt or solar charger have under 20 ohms and are much harder to defeat. I don't see how one strand would slow down intruders. I have found multiple stands can help with trespassers and stop crimes of opportunity-- calves don't disappear anymore.