IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. IA-22, NO. 12, MARCH/APRIL 1986
210
Stray Voltage: Sources and Solutions
TRUMAN C. SURBROOK, MEMBER IEEE, NORMAN D. REESE, AND ANGELA M. KEHRLE
is not a stray voltage source, but it can have an effect on the
magnitude of the level of voltage measured.
Most electrical distribution systems, both primary and
secondary, are intentionally connected to earth at frequent
intervals. This makes the earth part of the electrical network,
making it absolutely necessary for persons working with stray
voltage to realize that the earth is a conductor, connected in
parallel with the system neutral conductor. The earth does not
act as any kind of current "sink," absorbing electrons without
limit. Any current entering the earth will result in a corresponding exit from the earth at some other location. In addition
the entrance and exit points all have electrical resistance
resulting in voltage drops wherever these currents flow. Thus
animals, people, and equipment making contact between the
grounded system neutral conductor and earth may be exposed
I. INTRODUCTION
to a difference in potential sufficient to cause abnormal
S TRAY VOLTAGE, as it appears on farms, is a difference behavior and/or function.
Controlled experiments have been conducted at Michigan
in potential between some grounded surface or object and
State
University to determine the exact manner in which the
the earth. It may also appear between two different points on a
farm
and
electricity supplier neutral systems create neutral-tofloor or the earth. "The earth," as used in discussions of stray
The dual goals of this research were to
earth
voltages.
voltage, refers to a fictional "true earth" that is electrically
the
best
method of locating stray voltage sources
determine
neutral and is the reference for all stray voltage measurements.
to
evaluate
and
procedures for the elimination of stray
[2],
In practice any point 20 ft (6.1 m) or so in normal earth from a
were of such a magnitude as to affect
where
they
voltages
ground rod may be regarded as true earth.
Note that experts disagree on the
animal
behavior
adversely.
These neutral-to-earth potentials appear to be harmful to
of
that
cause
a change a animal behavior.
may
level
voltage
animals, particularly in the dairy environment. Definitive
1
often
chosen permissible value
V
to
be
the
most
While
seems
animal behavior studies are currently under way, but many
V have been used.
0.5
low
as
levels
as
of
voltage,
stray
that
these
small
when
potentials,
researchers today believe
Research on the effects of ac current on milking cows has
contacted in the parlor by milking cows, may cause nervous
behavior, kicking, and reduced feed and water intake, and been conducted in New Zealand [3], at Beltsville, [4], at the
may aggravate certain infections already present [1]. These University of Minnesota [5], and at Cornell University [6].
factors are alleged to have an adverse effect on milk This research shows that some cows may exhibit physical
reactions when as little as 2.0 mA passes through their bodies,
production.
Stray voltage arises because of voltage drop and ground while most cows react to 4.0 mA. These same studies have
faults. A concerned effort must be made to identify the cause suggested vales of electrical resistance for various paths
of the problem and to correct it. A number of solutions exist through the body of a cow. The lowest resistance path appears
today, but none provide a permanent solution for all stray to be between the muzzle and all four hooves, with Gustafson
voltage sources. The responsible solution to a stray voltage reporting values as low as 244 Q for one animal [5].
The resistance of the animal itself, however, is only part of
problem is to identify the source or sources accurately before
attempting a solution. The key is the understanding of the the total circuit resistance. The resistance of the contact
sources of stray voltage. Note that grounding, or the lack of it, between the animal and earth is the subject of current study at
Michigan State University, and it is believed that typical
Paper REPC 84-B5, approved by the Rural Electric Power Committee of contact resistance values may vary around several hundred
the IEEE Industry Applications Society for presentation at the 1984 Rural ohms resulting in total circuit resistances in the range of 1000
Electric Power Technical Conference, Nashville, TN, May 6-8. Manuscript
Q [7]. This value also appears in the early New Zealand work
released for publication January 11, 1985.
Abstract-Stray voltage is caused by voltage drop and ground faults
and may have its origin on the primary electrical distribution system or on
the customer's secondary electrical system. The rms value of the neutralto-earth voltage along a primary distribution line may be at a value of
zero some distance from the substation depending on the condition of the
conductor resistances, grounding resistances, and the amount of load.
Neutral-to-earth resistance is not the cause of stray voltage; however, the
value of this resistance to earth at a particular location will affect the level
of stray voltage. A four-wire single-phase feeder system supplying farm
buildings from a single metering point is effective in preventing on-farm
secondary neutral voltage drop, provided the four-wire system is extended
to all farm loads, and provided no high-magnitude ground faults are
present. Isolation of the primary and secondary neutral systems at the
distribution transformer is effective in preventing off-farm sources from
entering the customer's system. This separation may be accomplished
using a number of commercially available devices.
T. C. Surbrook and N. D. Reese are with the Departme-it of Agricultural
Engineering, Michigan State University, East Lansing, MI 48824-1323.
A. M. Kehrle is atRua Antonio Carvalho 47, Bairro dos Estados, 58000-
Joao Pessoa, PB, Brazil.
IEEE Log Number 8405837.
[3].
Using the preceeding assumptions it is apparent that it
requires a voltage of 2.0 V to drive a current of 2.0 mA
through a standing cow, this being the lowest current value to
0093-9994/86/0300-0210$01.00 © 1986 IEEE
211
SURBROOK et al.: STRAY VOLTAGE
result in an observable reaction in the animal. Neutral-to-earth
voltages below 1.0 V therefore are unlikely to cause an
adverse reaction in a dairy cow.
Ground Rod
1st Shell - 2.0 ohms
2nd Shell - 1.1 ohms
3rd Shell - 0.85 ohms
II. GROUNDING THE ELECTRICAL SYSTEM
The purpose of grounding a customer-owned electrical
system is discussed in the National Electrical Code (NEC) [8,
fine print note to sec. 250-1]. The system is grounded to limit
voltage transients due to lightning, line surges, or unintentional contact with higher voltage lines, to stabilize the
conductor-to-ground voltages during normal system operation, and to facilitate operation of protective devices for
ground faults.
Typical rural distribution lines are connected three-phase
four-wire wye and solidly grounded. Voltage classes vary, but
the 12470Y/7200-V system appears to be most common.
There are also areas in Michigan with extensive 4800-V delta
distribution. This system is not intentionally grounded but
does have enough capacitive coupling in most cases to allow
some ground current to flow during ground fault conditions.
This current is seldom high enough to operate feeder overcurrent devices.
The customer-owned electrical system is not always required to be grounded. The NEC [8, sec. 250-5 (b)] permits
certain electrical systems to "float" with respect to ground
with no solid connection to earth. The NEC [8, sec. 250-23
(a)] requires that there be a system connection to earth in
addition to the one installed by the electrical power supplier.
When several buildings are served by the same electrical
system on the same premises, the grounded system conductor
may be connected to earth at each building. This is usually
done in the case of agricultural buildings.
III. ELECTRICAL CONNECTIONS TO EARTH
A grounding electrode is used to connect an electrical
system to the earth, and [8, secs. 250-81, 250-83] specify what
type of electrodes may be used. An example of such an
electrode is a metal underground water piping system which
shall be used if present and in direct contact with the earth for
at least 10 ft (3.05 m). This water pipe system must, however,
be supplemented with an additional electrode. The metal frame
of a building must be used if it is effectively connected to
earth. In the case of many farm buildings, a ground rod -ill be
used. This is a 5/8-in (1.59-cm) diam galvanized steel rod
driven 8 ft (2.44 m) into the earth.
The earth has a finite resistivity expressed in Q * cm. Thus a
cube of earth, of 1000-9 cm resistivity, 1 cm on a side, will
have a resistance of 1000 Q between any two nonadjacent
sides. A typical resistivity value for sandy loam soil is in the
area of 4000 Q -cm.
When considering the grounding electrode shown in Fig. 1,
the earth surrounding such an electrode may be thought of as
being composed of successive 1-cm thick shells, each slightly
larger than the previous one. Each shell going outward from
the rod will therefore have a larger volume as the diameter
increases at each step. The larger volume means a lower
resistance as each shell may also be thought of as a large
number of 1-cm cubes, all connected in parallel. The first shell
Fig. 1. Electrode resistance.
around a typical ground rod will thus have a surface area of
about 1215.5 cm2 (188.4 in2) and a resultant resistance of
about 2 Q. The second shell then has a resistance of about 1.1
9 the third shell 0.85 9, and so on, with the resistance of each
successive shell decreasing steadily until they are so large as to
possess no appreciable resistance. After that point is reached,
succeeding shells are ignored. Taking all these resistances in
series results in a limiting value of about 20 9 for the rod. For
the purpose of analyzing the farm grounding system, this
resistance is thought of as being connected to a massive earth
medium of zero resistance. It is also assumed that the earth is
homogeneous and that it acts as a pure resistance. None of
these assumptions are strictly true, but they may be used for
the purposes of analyzing the farm grounding system.
The circuit diagram of Fig. 2 represents a simple singlephase rural electrical distribution system serving one farm
customer. Note that the earth forms a parallel path for neutral
current flow due to the numerous connections between the
neutral and earth. Obviously, some current must flow in the
earth as well as on the neutral conductor itself. Assume now
that 50 mA flows in earth electrode 1 of Fig. 2 where the
electrode is an 8-ft (2.44-m) driven ground rod with a
resistance of 20 Q. This current will thus produce a voltage
drop of 1.0 V across the resistance of the rod. This neutral-toearth voltage can be measured by connecting a voltmeter
between the ground rod and the earth a short distance from the
rod.
Lowering the resistance of the rod may appear to be an
answer to the problem, but the more common result will be to
increase the current through the lower resistanCe rod with the
result that the voltage across the rod remains nearly the same.
For example, if the electrode resistance were decreased to 8 Q
but the current increased to 90 mA, approximately 0.7 V
would remain as a neutral-to-earth potential. It is important to
determine what condition is causing the current to flow in the
earth. There will always be some current, but it is usually low
enough to avoid generating troublesome stray voltages.
IV. PRIMARY NEUTRAL-TO-EARTH VOLTAGE
Consider a single-phase primary electrical distribution
system originating from a substation. A 3-km section of 7200V grounded neutral distribution line was simulated by Michigan State researchers using a network-solving computer
program. Fig. 2 is a representation of the electrical network
used to study distribution system earth currents using this
model. The neutral conductor is grounded at the substation and
nine more times at equal spacings alone the line. The primary
neutral conductor was assumed to have a resistance of 0.424 9
for each equal line segment, and each transformer was
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. IA-22, NO.1 2, MARCH/APRIL 1986
212
RC9
4
1
Fig. 2.
tR2
RL
R3
RG
,R:;8ii
Distribution line model.
Fig. 3.
connected to true earth through a 25-Q grounding electrode.
Equal loading was applied to each of the nine transformers by
using a 6800-Q resistance between the primary ungrounded
conductor and the neutral.
The first simulation was conducted to study the effects of
substation grounding resistance on the neutral-to-earth voltages along the distribution line. Fig. 3 is a graph of these
potentials showing magnitudes and instantaneous polarity.
Note that the curve rises sharply at first, then levels off toward
the end of the line. It is to be expected that, as more sections
are added to the line, the line will approach the characteristics
of a long transmission line with a flat characteristic impedance
remaining unchanged as the line lengthens. These voltages
may be measured with a voltmeter, but the polarities will not,
of course, be observed. Note in Fig. 3 that the neutral-to-earth
voltage is lower at the substation when the substation ground
mat resistance is lowered to 1 Q from the more typical 5-Q
value and that the point on the line with zero neutral-to-earth
potential moves closer to the substation as the mat resistance is
lowered. The overall effect along the whole line, however, is
not nearly as great as might be expected, suggesting the the
substation ground mat resistance does not greatly affect
general neutral-to-earth potential conditions over the entire
line.
The next simulation was conducted to study the effect of the
customer's transformer grounding electrode resistance on the
neutral-to-earth potentials along the distribution line. The
results are shown in Fig. 4. All transformer grounding
electrode resistances are 25 Q except at the transformer
indicated. At this location, resistances of 5 and 50 Q were
substituted to observe the effects on neutral-to-earth potentials
along the distribution line. Note that the point of zero neutralto-earth potential shifted away from the substation as the
transformer grounding resistance was reduced. It is important
to remember that this is a simplistic model, and a more
detailed study is required before firm conclusions can be
drawn on effects of grounding resistances at a specific location
in this manner. Clearly, a major change in grounding
resistance at one location will have some effect on neutral-toearth potentials along the distribution line.
The final distribution line simulation shows the effects of
neutral conductor resistance on neutral-to-earth potentials
along the line. The simulation was made using 5 Q as the
substation ground mat resistance and 25 Q at each transformer
grounding electrode along the line. This is represented by the
smooth neutral-to-earth voltage curve of Fig. 5. An extreme
case of neutral resistance is simulated by placing 5 Q of
resistance at the point indicated in Fig. 5. The neutral-to-earth
8v
Primary neutral-to-earth potentials.
5 ohs
25 oim _
0
9
Resistance to earth
change here
Fig. 4.
Primary neutral-to-earth potentials.
5 olms in neutral
8v,
0
Base
4 wirI
e-;"
Fig. 5.
*
,
,
,-i
Case
9
Primary neutral-to-earth potentials.
potential profile changes sharply at the location of the high
resistance, resulting in improvement in neutral-to-earth potentials at some locations and worsening elsewhere.
The existence of neutral-to-earth potentials with opposite
polarities along the line helps explain voltages measured
during actual stray voltage investigations where zero or nearly
zero voltages were measured on a distribution line some
distance from either end of the line.
V. SECONDARY NEUTRAL-TO-EARTH POTENTIALS
Stray voltage on the secondary side of the distribution
transformer is caused by voltage drop on the neutral conductors and by ungrounded conductors faulting to earth. Ground
faults can cause potentially lethal voltages to appear on faulted
equipment as well as producing a farmwide neutral-to-earth
voltage. Both conditions can be prevented if all equipment is
grounded through a separate equipment grounding conductor
as required in [8]. Most cases of secondary neutral-to-earth
potentials are caused by excessive secondary neutral drop due
to one or more of the following conditions:
*
*
*
*
excessive resistance at a connector or termination,
feeder inadequately sized for the load carried,
excessive feeder length,
extreme imbalance of 120-V loads on the feeder.
213
SURBROOK et al.: STRAY VOLTAGE
Load
Fig. 6. Typical farm secondary distribution system.
Poor electrical system grounding is frequently considered to
be a cause of stray voltage, and many times it is suggested that
lowering this resistance will mitigate stray voltage conditions.
The results of this approach are variable and often disappointing. The following examples will serve to illustrate how onfarm sources of stray voltage occur and the effect of electrical
system grounding on these sources.
An analysis of stray voltages originating on the customer's
system must begin with a clear understanding of the secondary
neutral and grounding system. A typical farm electrical
distribution system with a central metering point and threewire single-phase feeders to each of the buildings is shown in
Fig. 6. The grounding electrode system on a typical farm
electrical system consists of a grounding electrode bonded to
the neutral at the transformer, another at the central metering
point, and one at each building. These grounding electrodes
are required by the NEC; however, they are frequently not
present on many farms. The buildings of Fig. 6 are shown
with the grounding system properly isolated from the neutral
except for the bond at the main disconnect. Most farm
buildings contain electrically operated equipment with
grounded metal parts making direct contact with the earth,
effectively lowering the total system grounding electrode
resistance at the building. Farm equipment, such as metal
stanchions embedded in concrete, may have a resistance to
earth from 100 Q or less to 1000 Q and more.
Voltage drop along any feeder neutral has the potential of
creating neutral-to-earth voltages at any point on the farm.
This is illustrated by the example of Fig. 6, where a 20-A lineto-neutral load is applied at building A. It is assumed that no
other loads are producing neutral current at the same time.
The amount of the neutral-to-earth voltage at a building will
depend on the grounding resistance at each building, the
amount of voltage drop present on each feeder neutral, the
phase angle of this voltage drop, whether or not an off-farm
source is also present, and whether or not a ground fault is
present.
An electrical circuit diagram for the feeder voltage drop
problem is shown in Fig. 7. The grounding electrode
resistance at the transformer, at the meter location, and at each
building is assumed to be 25 Q, the maximum desirable value
specified by [8] and [9]. It is assumed for this example that
grounding electrodes on the primary circuit are not a part of
this example except for the transformer grounding electrode.
This would be the case when the neutrals have been separated
at this transformer.
The neutral-to-earth voltages were then determined using
vra
Fig. 7. Secondary system schematic diagram. (VTE = voltage, transformer
neutral to earth; VME = voltage, meter neutral to earth; VAE = voltage,
building A to earth; RT = transformer, resistance to earth; RA = building
A, resistance to earth.)
the same computer program as was used to study stray voltage
on the primary distribution system. An analysis of the
secondary circuit can also be conducted using hand calculations as the circuit is relatively straightforward.
Note that the neutral-to-earth voltage at building A is 1.68
V. Also note a smaller value of neutral-to-earth voltage at the
other buildings, the metering point, and the transformer.
These other values of neutral-to-earth voltage will not be
identical, but they will be of the same order of magnitude
provided other voltage-producing conditions are not present.
Table I summarizes the values of neutral-to-earth voltages
obtained at the transformer, meter, and other buildings, and
building A with different values of neutral-to-earth resistance
at the transformer and at building A. The source of the stray
voltages is 0.08 Q of corrosion resistance in the feeder neutral
to building A. Note that lowering the building A grounding
resistance from 25 to 5 2 (Table I) reduces the stray voltage at
building A but increases it elsewhere on the farm. This effect
has been verified under controlled field conditions as well.
Increasing the grounding electrode resistance at building A to
200 Q simulates a case of a nonexistent grounding electrode
with the grounded equipment in the building providing the
only earth connection. The stray voltage under these conditions increases slightly at building A and is reduced at other
locations on the farm.
Stray voltage can also be caused by ground faults on
electrical equipment. To illustrate this, a ground fault is
introduced at building A of Fig. 6, and the new circuit
connections are shown in Fig. 8. The only source of stray
voltage in this example is the ground fault, and the feeder
neutral conductors have normal resistance. It is important to
note in this analysis that a ground fault can create a stray
voltage at any location on the farm, even in a different
building. The amount of stray voltage produced at locations
other than at the faulted equipment depends upon whether or
not a low-impedance equipment-grounding conductor is
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. IA-22, NO. 2, MARCH/APRIL 1986
214
TABLE I
NEUTRAL-TO-EARTH VOLTAGES PRODUCED AT KEY POINTS WITH
NEUTRAL RESISTANCES CAUSING THE STRAY VOLTAGE
Grounding Electrode
Resistance-0
Neutral-Earth Voltages
RT
Transfer
RA
Building A
VTE
Transfer
25
25
25
5
5
25
200
25
1.08
0.41
0.13
0.25
VME
Meter
VAE
Building A
0.98
0.31
0.03
0.15
1.00
1.68
1.97
1.84
~~~~~~~~~~Lcad
120v
T
VIE
~~~~~~A
m
-1O
Ve
.
Is
w
ra
Ground
I Fault
Fig. 8. Secondary system with ground fault.
present and also upon the fault impedance path comprised of
the fault resistance and the equipment-to-earth resistance in
series. Table II summarizes the stray voltage produced by
different fault resistances to earth. All grounding electrode
resistances to earth are set at 25 Q for this example. The
current flow in the circuit is determined by the load resistance
and the fault resistance.
A nearly equal neutral-to-earth voltage is produced at all
locations on the farm. The level of neutral-to-earth voltage
decreases as the fault resistance to earth increases. When a
fault does occur in a piece of farm electrical equipment the
resistance of the fault and the equipment-to-earth resistance is
almost always more than 100 9 [10]. Keep in mind that the
fault current uses the earth as a conductor when a lowimpedance equipment-grounding conductor is not present. It is
important to install equipment-grounding conductors that will
remain at a low impedance over time on all farm electrical
equipment.
TABLE II
NEUTRAL-TO-EARTH VOLTAGES PRODUCED AT KEY POINTS WITH A
GROUND FAULT AT BUILDING "A" CAUSING THE STRAY VOLTAGE
Fault-to-Earth
Resistance-Q
VTE
Transfer
20
100
200
300
20.85
4.95
2.60
1.15
Neutral-to-Earth Voltages
VAE
VME
Meter
Building A
20.71
4.84
2.50
1.04
20.31
4.44
2.09
0.64
farm neutral either by opening the bond between the primary
and secondary neutrals at the transformer or by introducing an
impedance between the neutrals. Some electrical power
suppliers will open the bond and add another grounding
electrode at the transformer on the secondary neutral [11].
Another approach is to install a fast-acting thyristor switch
VI. SOLUTIONS
between the primary and secondary neutrals that will close in
the event of a high-voltage contact. Still another commercial
before
of
voltage
the
sources
stray
It is important to identify
available is a saturable reactor installed between the
device
"shotgun"
the
Taking
solutions.
at
undertaking attempts
[12]. These techniques will not stop on-farm sources
neutrals
could
that
data
valuable
cover
up
simply
may
approach
become important at a later time. A publication describing a from reaching the animals.
A four-wire feeder system on a farm with the neutral and the
simplified approach to stray voltage source identification is
available from the authors [2]. The source can be traced to on- equipment-grounding conductor bonded only at the central
farm and/or off-farm origins. The on-farm sources can and metering point will prevent secondary neutral voltage drop
should be corrected to reduce the neutral-to-earth voltage to from being applied to the equipment where it may affect
levels that will not be bothersome to animals. Some new animals [13]. The four-wire system must, however, be run to
devices are coming on the market that have the potential of all farm loads to be effective because, as illustrated in Fig. 7, a
offsetting neutral-to-earth voltage without eliminating the voltage drop to one building may produce a stray voltage at
source. It is important, however, to identify and eliminate the another. The four-wire feeder system will not, however,
prevent on-farm ground faults from producing stray voltage.
source whenever possible.
The fault current will still enter the earth and flow to the
to
the
on
coming
from
can
be
source
prevented
off-farm
An
215
SURBROOK et al.: STRAY VOLTAGE
grounding electrodes, thus producing the same effects as
illustrated in Table II.
An equipotential plane may be established in critical areas
where animals feed, drink, or are milked. This approach is
encouraged with all new construction, but attempts to establish
equipotential planes in existing facilities have met with
variable success. The greatest control is necessary to provide a
way for animals to approach an equipotential plane without
being exposed to a bothersome difference in voltage.
VII. CONCLUSION
Stray voltage may be produced on the primary electrical
distribution system or on the secondary electrical system. The
causes are voltage drop and ground faults. Grounding will
affect the level of stray voltage, but it is not in itself a cause.
The source can be identified and, in many cases, eliminated.
When this is not practical, commercially available devices are
available that will mitigate the stray voltage to a level that is
believed to be tolerable to the animals.
[13]
installations of magnetic saturation blockers for minimization of stray
voltage on dairy farms," ASAE paper 156-170, 1984.
T. C. Surbrook, N. D. Reese, R. J. Gustafson, and H. A. Cloud,
"Designing facilities to prevent stray voltage," in Proc. 2nd Nat.
Dairy Housing Conf., 1983.
Truman C. Surbrook (AM'83) received the B.S.,
M.S., and Ph.D. degrees in agricultural engineering
from Michigan State University, East Lansing, in
1965, 1969, and 1977, respectively.
He has worked in the area of electrical power as
applied to agriculture for 20 years. Presently, he
holds the position of Associate Professor with
responsibilities in teaching and research. His areas
of research involve neutral-to-earth voltage, electri> cal wiring for agriculture, and robotics as applied to
agricultural machinery.
Dr. Surbrook is a licensed Master electrician and serves as an alternate
member of the National Electrical Code Making Panel 1l. He is a Registered
Professional Engineer in the State of Michigan.
REFERENCES
[1] H. A. Cloud, R. D. Appleton, and R. J. Gustafson, "Stray voltage
problems with dairy cows," Agricultural Extension Service, Univ. of
Minnesota, St. Paul, North Central Regional Extension Pub. 125,
1980.
[2] T. C. Surbrook and N. D. Reese, "Stray voltage measurement and
source identification procedure," Michigan State Univ., Agricultural
Eng. Information Series AEIS 484, Oct. 1983.
[3] M. W. Woolford, "Small voltages on milking plants," in Proc. 2nd
Seminar Farm Machinery and Engineering, Hamilton, New Zealand,
1972, pp. 41 47.
[4] A. M. Lefcourt and R. M. Akers, "Endocrine responses of cows
subjected to controlled voltages during milking," J. Dairy Sci., vol.
65, no. 11, pp. 2125-2130, 1982.
[5] R. J. Norell, R. J. Gustafson, R. D. Appleman, and J. B. Overmier,
"Behavioral studies of dairy cattle sensitivity to electrical currents,"
Trans. ASAE, vol. 26, no. 5, pp. 1506-1511, 1983.
[6] D. V. Heinke, R. C. Gorewit, N. R. Scott, and D. M. Skyer,
"Sensitivity of cows to transient electrical current," ASAE paper 823029, 1982.
[7] T. C. Surbrook and N. D. Reese, "Stray voltage on farms," ASAE
paper 81-3512, 1981.
[8] National Electrical Code, National Fire Protection Association,
Batterymarch Park, Quincy, ME, 1984.
[9] National Electrical Safety Code, Inst. Elec. Electron. Eng., 1984.
[10] T. C. Surbrook and N. D. Reese, "Grounding electrode to earth
resistance and earth voltage gradient measurements," ASAE paper 823507, 1982.
[11] L. H. Soderholm, "Stray voltage problems in dairy milking parlors,"
ASAE paper 79-3501, 1979.
[12] J. Donald, C. M. Hertz, and I. Winsett, "Results of initial field
Norman D. Reese received the B.E.E. degree from
Cleveland State University, Clevela}id, OH, in
- ; _
~~1961.
He worked 20 years in the electrical utility
industry, both for power companies directly and as
a consultant. He has been in the Agricultural
Engineering Department at Michigan State University the last four years, teaching courses in electrical
technology. His work experience includes design of
protection systems for EHV transmission lines and
m
large plants as well as distribution system design.
His foreign assignments have taken him to Brazil, Saudi Arabia and Pakistan,
and he has done work for clients in Turkey, Bolivia, and Iran.
Mr. Reese is a licensed Master electrician. He is a Registered Professional
Engineer in the State of Michigan.
S
X
Angela M. Kehrle was born in Joao Passoa, Brazil.
She received the B.S.E.E. degree from Federal
University of Paraiba, Brazil, and the M.S. degree
in agricultural engineering from Michigan State
Univeiiity in 1970 and 1984, respectively.
She has five years' experience in rural electrification with the electric company, SAELPA, serving
the State of Paraiba, Brazil. Presently she is an
Electrical Engineer for the same company in Joao
Passoa.