Interactions

The grounding practice in the utility industry forces all living organisms to be continuously in physical contact with the electrical distribution system. The extensive grounding of the neutral in the distribution system also forces electrical currents to be present to a greater or lesser degree in all materials making up the environment of living organisms. Of course the living organisms, since they are themselves conductors of electricity and in contact with materials carrying electric currents, are basically plugged into the electrical circuitry of the distribution system.

The use of water pipes and other conductors in the earth to carry the neutral current of distribution systems has the effect of decreasing the current in the neutral wire. In addition, when unshielded distribution wires are buried in the earth, the neutral slowly corrodes, also increasing the amount of the neutral current in the earth. If the neutral and the high voltage wires carry the same current, the magnetic fields in the vicinity of the lines are relatively small, because the magnetic fields of the two lines nearly cancel each other. When the current in one wire is much less than in the other, the magnetic field is only partially canceled. This condition greatly increases the magnetic field in the area of distribution lines and enhances the range of these fields. In homes and businesses there is also an increase in the 60 Hz magnetic fields from the ground currents in water pipes and other conducting material. This condition is very effectively presented in a paper prepared for Austin, Texas {Preston, 1989)

Alternating current in the ground sets up alternating electric and magnetic fields. These electric fields give rise to electrical potentials that can induce currents in living organisms in contact with the ground. Alternating magnetic fields, by their very nature, also produce currents in conducting materials. Electric currents in living organisms, regardless of the mechanism that may produce them, are indistinguishable from one another. The currents simply access the body differently. In addition to the possibility of inducing an electric current in the body of living organisms, the electric and magnetic fields may independently or synergistically interact with parts of the body. Complicating the understanding of the interaction of these ground currents with living organisms is the effect of earth materials on the 60 Hz current entering the earth. The non-linear characteristics of the earth distort the 60 Hz sine wave, even affecting the natural processes that produce direct current in the earth. Thus ground currents from the power system are transformed into some combination of 60 Hz, harmonics, and direct currents.

An assumption has been made, in the design of the electrical distribution system, that the grounding of the system creates a constant electrical potential on the earth’s surface. This is called an equipotential plane in the dairy industry. Using that assumption, all living organisms are living on an equipotential plane, connected to the neutral of the electric distribution system. To justify this ground connection, it is also assumed that an equipotential plane is an electrically safe place to be. The stray voltage problems in the dairy industry, however, have shown that when the neutral of the distribution system is connected to the earth, the earth is neither a plane of constant electrical potential nor an electrically safe place. Livestock producers are especially aware that lightning or a fault in a distribution line can kill animals if they happen to be in the path of the electric current in the ground. Dairy operators are frequently required by state codes to construct equipotential planes in their barns as a means of avoiding electric shocks for the cows. Unfortunately the equipotential plane is a good conductor which attracts a greater percentage of the ground currents, causes the cows to be exposed to greater continuous currents, and frequently increases stray voltage effects (Dahlberg and Falk 1995).

Surveys and farm evaluations and investigations have provided a significant body of information concerning the effects of ground currents (Hartsell, Dahlberg, Lusty, and Scott 1994; Dahlberg and Falk 1995; Marks, Ratke and English 1995; Kelly 1998). As mentioned previously, the main documentation of electrical effects in dairy barns historically involves ground faults. When electric current enters the earth from a high voltage wire, the event is called a ground fault. The high voltage wire can be from either the primary or the secondary system. Usually discussions of ground faults center on problems in the secondary system. Well-known effects from ground faults include behavioral, health, and production problems for confined livestock, such as dairy animals, and both human and animal electrocution (Dahlberg and Falk 1995).

On dairy farms, current in the ground is associated with behavioral, health and production effects in cows. It is very important to carry this association to the next step, which is the determination of how these currents interact with the cow to produce the physical effects. The presence of ground currents implies long-term, continuous exposure to low-level electrical currents. Worldwide research and investigations of both animal and human health problems in dairy barns have demonstrated that small continuous currents (as low as a fraction of a microamp) can affect well being. Bjorn Nordenstrom, among others, has suggested models that portray the bodies of living organisms as having electric circuits with small currents actually controlling life (Nordenstrom 1983). Appropriate electric currents of small magnitudes within the circuits of the body are vital to good health. The bodies of living organisms generate these currents and naturally provide the magnitudes that afford good health.

Using Nordenstroms models, one can imagine that exposure to an electric and magnetic environment could affect the currents in the circuits of the body, either positively or negatively. The medical community has utilized this positive potential in a number of ways. Negative changes caused by these currents, however, would require the body to correct the change. Such an event could be classified as a stress on the body. It would be logical to conclude that exposure to certain electrical conditions can be equivalent to initiating a stress. If the currents in the floor of the barn set up an electric and magnetic environment that causes inappropriate currents in the body of the cow or the human, the experienced effects would likely be similar to those caused by other stresses. Unfortunately, the research community has been reluctant to investigate this source of stress on animals and humans. The traditional research model continues to assume that negative health effects are possible only in the presence of physical shock.