3.0
Transmission Line Options
3.1
Technical Analysis
Great River Energy has examined four different alternative transmission line projects
that could remedy the system deficiencies. Great River Energy’s preferred option is a
69 kV project. The other three are 115 kV projects. The options are described below:
Option 1 - Athens to Martin Lake 69 kV Transmission Line (Great River Energy’s
preferred solution)
This option would involve the construction of approximately 10.2 miles of 69 kV
transmission line between the Connexus Energy Martin Lake Substation and the Great
River Energy Athens Substation (see Figure 3-1).
This option provides a redundant transmission source to the Martin Lake Substation and
allows for additional growth in electrical demand to be supported along the Highway 65
corridor via the Linwood Substation. Facilities could be easily integrated into the existing
system with 69 kV construction.
Option 2 - Chisago County-Martin Lake-Coopers Corner 115 kV line and Coopers
Corner 115/69 kV Substation
This option would involve the construction of approximately 25 miles of 115 kV
transmission line between the Xcel Energy Chisago County Substation, the Martin Lake
Substation, and the Coopers Corner Substation. A new 115/69 kV transformer would
be established at the Coopers Corner Substation and the Martin Lake Substation would
be converted to 115 kV service. Additionally, the Coopers Corner-Athens 69 kV line
would be rebuilt as a 69 kV line with equipment to accommodate the higher line flows
that would result on this line with the new 115 kV line addition (see Figure 3-2).
This option is essentially a duplicate of the preferred alternative (Option 1), but would
require that significantly more transmission line be built, and therefore, more new right
of way be acquired. Additionally, the increased line mileage between breakers adds to
the exposure of the line, reducing reliability.
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Figure 3-1: Martin Lake-Athens 69 kV Line
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Figure 3-2: Chisago County-Martin Lake-Coopers Corner 115 kV Line
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Option 3 - Chisago County-Martin Lake-Coopers Corner-Blaine 115 kV line,
Coopers Corner 115/69 kV Substation, and Blaine 230/115 kV Substation
Modifications
Great River Energy investigated continuing the 115 kV line proposed in Option 2 south
to the Blaine Substation. This would require about 50 miles of new 115 kV line and
would provide redundant 115 kV transmission feeds to the Coopers Corner Substation.
Much of this line would likely be built on existing 69 kV transmission line corridors,
replacing the existing 69 kV circuits with new 115-69 kV double circuit structures (see
Figure 3-3).
However, in addition to the drawbacks cited in Option 2, construction outages would
likely be difficult to schedule because significant reconstruction of the Great River
Energy 69 kV system would likely be required. Also, due to the significant 115 kV line
length between substations, there would be additional line exposure, thus the system
would not be as reliable as the preferred option.
Option 4 - Blaine-Martin Lake-Athens-Dalbo 115 kV line, Athens 115/69 kV
Substation, Rush City-Dalbo-Milaca 230 kV line, and Dalbo 230/115 kV Substation
Option 4 would require building a new 115 kV line between the Blaine, Martin Lake and
Athens substations, and a new Dalbo 230/115 kV Substation. A new 230 kV line
between the Milaca, Dalbo, and Rush City substations would be required to support the
115 kV system. This 230 kV line would provide a 230 kV loop to the Milaca Substation
and create a 230 kV ring around the Great River Energy 69 kV system. A new
115/69 kV transformer would be added at the Athens Substation (see Figure 3-4).
This would involve approximately 110 miles of 230 and 115 kV line, a new 115/69 kV
transformer at the Athens Substation, a new 230/115 kV substation at Dalbo,
modifications at the Blaine, Rush City, and Milaca substations, and a voltage conversion
of the Martin Lake Substation. A second 230 kV line into the Milaca Substation would
be beneficial to the reliability of this substation.
Although this is a technically feasible option from a system standpoint, it is clearly not
justifiable given the drawbacks. It clearly cannot be justified from a cost standpoint and
developing a 230 kV system would have a much more significant environmental impact
the preferred option; a new 60 mile corridor would need to be developed. Much of the
115 kV system would likely be double circuited with the existing 69 kV system, which
would likely make scheduling construction outages difficult. Also, the permitting and
construction schedule for a project of this magnitude may take years, which does not
address the required timelines for 69 kV system improvements. Like other alternatives,
the 115 kV line exposure would be much greater than the exposure offered by the
proposed project, thus reduced reliability would be expected with this alternative. There
is also lack of space at Athens Substation for 115 kV expansion, which would make
siting a 115/69 kV transformer there extremely difficult.
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Figure 3-3: Chisago County-Martin Lake-Coopers Corner-Blaine 115 kV Line
13
Figure 3-4: Blaine-Martin Lake-Athens-Dalbo 115 kV Line
and Rush City-Dalbo-Milaca 230 kV Line
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3.2
Cost and System Efficiency Analysis
The estimated costs for each of the alternatives considered are tabulated in Table 3-1.
These include the project costs incurred by Great River Energy, its member
cooperatives, and other transmission-owning utilities that would need to modify their
electrical facilities to accommodate the change.
Additionally, each of the projects will reduce the amount of line losses (energy
generated but not deliverable) currently occurring. These efficiency improvements in
delivering electricity to the area Connexus and East Central substations are realized
with each of these projects and are summarized in Table 3-2.
Table 3-1 Estimated Cost Factors for Options 1- 4
Estimated Cost
Option 1: Martin
Lake-Athens
69 kV line
Option 2:
Chisago CountyCoopers Corner
115 kV line
Option 3: BlaineCoopers CornerMartin LakeChisago County
115 kV line
Option 4: BlaineMartin LakeAthens-Dalbo
115 kV line
$6,537,000
$39,700,000
$67,340,000
$124,480,000
Table 3-2 System Peak Loss Improvements for Options 1- 4
System Peak Loss Improvements Estimated Yearly System Loss Savings Value Option 1: Martin Lake‐Athens 69 kV line Option 2: Chisago County‐Coopers Corner 115 kV line Option 3: Blaine‐
Coopers Corner‐
Martin Lake‐
Chisago County 115 kV line Option 4: Blaine‐
Martin Lake‐
Athens‐Dalbo 115 kV line 0.7 MW 3.2 MW 3.7 MW 3.3 MW $169,300 $773,900 $894,850 $798,100 15