The high voltage transmission utility I retired from investigated a dairy problem that turned out to be improper/not enough ground bonding. It was a 60 cycle problem, no harmonics involved. George's pictures illustrate the problem well. The comments on isolation of neutral conductors from ground and the quality of the overall grounding system are spot on. Grounding in a dairy just about has to be nuclear quality. No shortcuts allowed.
Are there any overhead high voltage transmission lines near the dairy? They will establish electric fields that the cows walk within. I hope that is not your problem, because it is a really ugly one to deal with.
As others have already pointed out, cows are very sensitive to small voltages. The trick is to establish an equipotential plane that the cows stand on so that they cannot touch something that is not bonded to that plane.
With respect to water tanks and stuff like that, if you cannot eliminate stray voltages to remote earth you may be able to live with them by establishing a ground mat around the tank. The tank and the immediate area surrounding it sit on the mat and are all at the same potential. It may be slightly different potential from remote earth, but the immediate area surrounding the tank is all at the SAME potential. The cow can drink from the tank without establishing a conductive path to ground that allows leakage current from the tank to remote earth.
Can you scrounge together a long run of test lead wire for your DVM? My recollection is that we wound up doing was measuring the voltage difference between various points in the dairy and the ground at the pole. Once we figured out that not all "ground points" within the dairy were at the same potential we tried to figure out how to deal with it. Think "never get in series". The cow must never be in series with stray current flow to remote earth. If you cannot eliminate this current flow figure out how to manage it so the cow is shunted by your bonding system.
Are there any overhead high voltage transmission lines near the dairy? They will establish electric fields that the cows walk within. I hope that is not your problem, because it is a really ugly one to deal with.
As others have already pointed out, cows are very sensitive to small voltages. The trick is to establish an equipotential plane that the cows stand on so that they cannot touch something that is not bonded to that plane.
With respect to water tanks and stuff like that, if you cannot eliminate stray voltages to remote earth you may be able to live with them by establishing a ground mat around the tank. The tank and the immediate area surrounding it sit on the mat and are all at the same potential. It may be slightly different potential from remote earth, but the immediate area surrounding the tank is all at the SAME potential. The cow can drink from the tank without establishing a conductive path to ground that allows leakage current from the tank to remote earth.
Can you scrounge together a long run of test lead wire for your DVM? My recollection is that we wound up doing was measuring the voltage difference between various points in the dairy and the ground at the pole. Once we figured out that not all "ground points" within the dairy were at the same potential we tried to figure out how to deal with it. Think "never get in series". The cow must never be in series with stray current flow to remote earth. If you cannot eliminate this current flow figure out how to manage it so the cow is shunted by your bonding system.