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Public Service Commission of Wisconsin
Public Service Commission of Wisconsin

Stray Voltage Phase I and Phase II
Combined Database Summary
January 26, 2006

Since 1988, the Public Service Commission (PSC) has been accepting data filed by the five major
investor-owned utilities (IOUs) regarding certain aspects of their stray voltage (SV) Phase I
investigations. Recently, the database has been expanded to include extra fields from their Phase II
investigations. The Wisconsin Electric Cooperative Association has also been submitting some data
on behalf of a number of its members in the last few years. Please refer to the glossary in Appendix A
for definitions of various terms and acronyms use in this document. All voltage and current data is
express as rms, 60-Hz, AC, steady state.

To date, the PSC SV database has entries from 7,441 farms. A separate database of Phase II primary
profiles now has data on 12,430 grounded distribution poles. The data from these databases is
summarized in this paper. A statistical summary for each parameter is presented along with
correlations and contrasts between some of the parameters. All of the submitted data is accepted as it
comes in. Some data are suspect as the magnitudes do not seem within a reasonable range, but are
included and will appear as statistical outliers. Entries of zero or blank fields are treated the same as
a no report condition.

Farms reported per year in PSC database
0
100
200
300
400
500
600
700
800
198
8
198
9
199
0
199
1
199
2
199
3
199
4
199
5
199
6
199
7
199
8
199
9
200
0
200
1
200
2
200
3
200
4
200
5
year
fa
r
m
s
















There were very few submissions to the database in the first five years of record keeping, but the last
thirteen years has shown a relatively steady level of submissions. Only half of the 2005 data had been
received by the time this report was prepared.

The data can be analyzed and presented using several statistical methods. Each numerical parameter
has an overall average along with a 5-number summary that lists the minimum value, the median

1 value, the maximum value along with the first and third quartile values. The distribution of values for
each parameter is summarized in a graph or a table that lists the percent of entries that fall within a
specific range of values. These statistics provide a standard yardstick against which any subsequent
data point collected in the field can be compared to see how it measures up and where it falls within
the known range of reported values.

A historic trend of the values versus the year they have been submitted is also presented in graphic
form. Lastly, a correlation is usually made with the most important parameter, the average cow
contact current, to see if the parameter in question may have any influence on the magnitude of current
that can be measured at the animal contact point or itself be influenced by the cow contact current.


Farm s in PSCW Utility Database - Trend
0
1000
2000
3000
4000
5000
6000
7000
8000
198
8
198
9
199
0
199
1
199
2
199
3
199
4
199
5
199
6
199
7
199
8
199
9
200
0
200
1
200
2
200
3
200
4
200
5
YEAR
D
a
t
a
b
a
s
e
to
ta
l














The data are divided up into electrical and similar parameters and farm and miscellaneous parameters
as follows.

Electric parameters
Farm/misc. parameters
Location within WI
Rshunt
Load box test
Rprimary
Fencer status
Distance to substation
Vp Primary neutral-to-
reference voltage
Load box test Rfarm
Stanchion/other milking
Grounds per mile
Vs Secondary neutral-to-
reference voltage
Load box test K-factor
Pipeline/other delivery
End-of-line status
Vcc Cow contact voltage
Load box test CRR
current return ratio
Electric/pneumatic
pulsation
Primary Voltage
Icc Cow contact current
Secondary neutral
voltage drop test
Vdrop
Herd size
Neutral Conductor
Resistance/mile
Vcc source on/off farm
status
Primary profile current
Ipp
Test program
Transformer kVA rating
As-found mitigation
Primary profile
resistance Rpp
Milk production level
Measured Vps drop
Recommended on-farm
mitigation
Primary profile voltage
Vne
Somatic cell count (SCC)
level
Secondary phase
arrangement
Recommended off-farm
mitigation


Rsource
Recommended neutral
isolation



2 ELECTRICAL PARAMETERS

1) Distance to Substation
This parameter is defined as the circuit miles from the farm being investigated to its serving
distribution substation.

7 number
summary

UNIT

Distribution
Range
% in
range
Average
6
mile

0.1 - 1.0
3.3
Minimum
0.1
mile

1.1 - 3.0
20.1
1
st
quartile
3.5
mile

3.1 - 6.0
39.6
Median
5
mile

6.1 - 10.0
25.5
3
rd
quartile
7.8
mile

10.1 - 15.0
9.1
Maximum
55
mile

15.1 - 21.0
2.0
Entries, N
7,068


21.1 & up
0.4

Average distance to substation trend
3
3.5
4
4.5
5
5.5
6
6.5
7
7.5
1988 1989 1990 199
1
1992 1993 199
4
1995 1996 199
7
1998 1999 2000 2001 2002 2003 2004 200
5
year
m
ile
s















The trend indicates that in the early years of the SV program at the PSC, most farms that were
investigated by the IOUs were closer to the substation. Recently, there is a trend to investigate farms
that are farther away from the substation. From 1988 to 2005, the average distance has increased 44%.

Avg. Icc vs. Dist. to substation
1.18
0.92
0.84
0.78
0.67
0.94
0.71
0
0.2
0.4
0.6
0.8
1
1.2
1.4
.1 - 1.0
1.1 - 3.0
3.1 - 6.0
6.1 - 10.0
10.1 - 15.0 15.1 - 21.0 21.1 & up
M iles range
m
A
Correl Coeff. = -0.04
N = 6772















3
There is a slight visual correlation between cow contact current levels and being too close or too far
from the substation. The data is skewed by the fact that early investigations (1988 1993) found
higher levels of stray voltage than are found today and these farms were close to the substation. The
mathematical correlation coefficient indicates a very weak link between distance and cow contact
current.

2) Location

One of nine specific areas of the state where the farm is located is submitted as a data point. The areas
are named central, east central, north central, northeast, northwest, south central, southeast, southwest
and west central. They are determined by a table look-up based on the county in which the farmstead
is located. The average cow contact voltage and the average secondary neutral-to-reference voltage for
each of the nine locations is shown in the following table.

Avg Vcc (Volts) vs. location:
Avg Vcc
0.47
0.28
0.33
points
315(NW)
645(NC)
428(NE)
Avg Vcc
0.38
0.33
0.30
points
362(WC)
824(C)
1,612(EC)
Avg Vcc
0.51
0.48
0.62
points
987(SW)
1,214(SC)
161(SE)
total points
6,548


Avg Vs (Volts) vs. location:
Avg Vs
1.42
1.07
1.19
points
320(NW)
645(NC)
427(NE)
Avg Vs
1.29
1.18
1.03
points
369(WC)
827(C)
1,503(EC)
Avg Vs
1.31
1.28
1.44
points
981(SW)
1,205(SC)
159(SE)
total points
6,436
We can calculate an average K-factor (defined as Vcc/Vs) for each of the nine locations as follows:

Average K-factor (N = 6,079)
in percent from above data
Overall average = 29%
29(NW)
24(NC)
27(NE)
28(WC)
26(C)
27(EC)
32(SW)
33(SC)
37(SE)

The average K-factor for the state is therefore 29% which agrees well with the typical value of 33.3%
predicted by the PSC REPS team.

3) Grounds per mile

This parameter is defined as the average number of neutral-to-earth grounding electrode connections
on the primary distribution system per mile in the area of the farm towards the substation.

4
7 number
summary

UNIT
Distribution
Range
% in
range
Average
13
Grnds/mile

1 - 4
0.6
Minimum
1
Grnds/mile

5 - 8
5.0
1
st
quartile
9
Grnds/mile

9 - 12
53.7
Median
12
Grnds/mile

13 - 16
20.1
3
rd
quartile
15
Grnds/mile

17 - 20
11.1
Maximum
33
Grnds/mile

21 - 24
6.9
Entries, N
6,418


25 & up
2.6
Wisconsin has always required nine grounds per mile in any continuous one mile section for overhead
distribution systems and 4