20060717IPC to Staff 25, 75, part II.pdf

APPENDIX A
Method of Study
The study methodology inserts the proposed generator up to the maximum requested summer
output of 73 MW into the selected WECC power flow case and then, using the PowerWorld
Simulator powerflow program, examines the impacts of the new resource on Idaho Power
transmission system (lines, transformers, etc.) within the study area under various
operating/outage scenarios. The WECC and Idaho Power reliability criteria and Idaho Power
operating procedures were used to determine the acceptability of the alternatives considered.
The WECC case is a recent cases modified to simulate stressed but reasonable pre-contingency
energy transfers utilizing the IPC system.
Acceptability Criteria
The following acceptability criteria were used in the power flow analysis to determine the
acceptability of the alternatives:
Loadings on transmission lines and transformers should not exceed 115% of the
continuous rating, immediately flowing any N-1 outage. Loading on the Midpoint 230
kV series capacitors should not exceed 135% of the continuous rating, immediately
flowing any N-1 outage. These loadings levels of 115% on transmission lines and
transformers and 135% on Midpoint series capacitors correspond to IPCo s 30 minute
emergency equipment ratings. Any loadings immediately following an N-1 outage
less than the 30 minute emergency rating is acceptable.
Loadings which are less than the 30 minute emergency equipment ratings, but greater
than the equipment continuous ratings , must be reduced to the continuous ratings by
generation curtailments, re-dispatch, or some other operating procedure. Any remedial
action schemes(RAS) or other transmission switching, must be judged to be reasonable
before the alternatives performance can be deemed acceptable.
The continuous rating of equipment is assumed to be the normal thermal rating of the
equipment. This rating will be as determined by the manufacturer of the equipment or
as determined by Idaho Power. Less than or equal to 100% of continuous rating for
transmission lines and transformers is acceptable. Less than or equal to 110% of
continuous rating for the Midpoint 230 kV series capacitors is acceptable.
Transmission voltages , under normal operating conditions, are maintained within plus
or minus 5% (0.05 per unit) of nominal. Therefore, voltages greater than or equal to
95 pu voltage and less than or equal to 1.05 pu voltage are acceptable.
- -
The stable operation of the transmIssTonsystemfequITeS anadequate supply of volt-
amperes reactive (V ARs) to maintain a stable voltage profile under both steady-state
and dynamic system conditions. An inadequate supply of V ARs will result in voltage
- -
14-
decay or even collapse under the worst conditions. Idaho Power designs its system to
integrate Network Resources at full capability during specified outage conditions.
Equipment/line/path ratings used will be those that are in use at the time of the study or that are
represented by IPC upgrade projects that are either currently under construction or whose
budgets have been approved for construction in the near future. All other potential future
ratings are outside the scope of this study. Future transmission changes may, however, affect
current facility ratings used in the study.
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APPENDIX B
l Outages That Produce Overloads On The Existing System
The following one line diagrams depict system performance following the seven N-l outages
that produce overloads which exceed the continuous rating of facilities. Figure 1 on page 4
depicts the operation of the existing system with no outages. The combination of heavy hydro
and peaker generation in the Mountain Home area, and 1100 MW east to west transfers on
Midpoint West, results in the Mountain Home Junction to Lucky Peak and Lucky Peak to
Micron 138 kV lines being loaded to 98% & 99% respectively, prior to any outages.
Mld olnt West = 981
Existing System - Midpoint to Boise Bench #3 230 kV Outage
Figure 9
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Mld olnt West = 951
Existing System - Rattlesnake to Boise Bench #2 230 kV Outage
Figure 10
Mld olnt West = 997
Existing System - Midpoint to Rattlesnake #2 230 kV Outage
Figure 11
17-
MldDolnt West = 1053
Existing System - Midpoint to DRAM #1230 kV Outage
Figure 12
Mld olnt West = 1085
Existing System - CJ Strike to Bowmont 138 kV Outage
Figure 13
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Mld olnt West = 1072
Existing System - Lucky Peak to Micron 138 kV Outage
Figure 14
MldDolnt West. 1094
Existing System - Evander Andrews to CJ Strike 138 kV Outage
Figure 15
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i .
LARGE GENERATOR INTERCONNECTION
FEASIBILITY STUDY REPORT
for the
230 KV INTERCONNECTION OPTION
BENNETT MOUNTAIN POWER PLANT
for
Idaho Power Company - Power Supply, Interconnection Customer
for connection of
A 170/196 MW SIMPLE CYCLE GAS TURBINE PEAKING PROJECT
BENNETT MOUNTAIN POWER PLANT
IDAHO POWER COMPANY, Transmission Provider
TRANSMISSION SYSTEM
FINAL REPORT
September 30, 2005
1.0 Introduction
Idaho Power Company - Power Supply has contracted with Idaho Power Company (IPC) to
perform a Large Generator Interconnection Feasibility Study for Network Resource
Interconnection Service at 230 kV for the integration of a new 170/196 MW simple cycle gas
turbine peaking project. The proposed location is the Bennett Mountain Power Plant near
Mountain Home, Idaho.
This report documents the basis for and the results of this Feasibility Study. It describes the
proposed interconnection alternatives, the study cases used, outage scenarios assumed and
results of all work in the areas of concern.
Summary
The performance of three interconnection alternatives was evaluated to integrate a simple cycle
gas turbine with a summer rating of 170 MW and a winter rating of 196 MW, located at
Bennett Mountain Power Plant, into the Idaho Power System. Alternative #3 is the
recommended alternative.
Alternative #1:
Alternative #2:
Construct a radial 230 kV interconnection line, from a new 230 kV substation
at Bennett Mountain, to the Midpoint-Boise Bench #3 transmission line.
Several N-l contingencies resulted in unacceptable overloads for this
alternative. Additional improvements , of a 230/138 kV transformer at
Rattlesnake with a new 138 kV line from Rattlesnake to Mountain Home
Junction, were evaluated in an unsuccessful attempt to achieve acceptable
performance under N-l outage conditions.
Construct two new 230 kV transmission lines from Bennett Mountain to
Evander Andrews and Evander Andrews to Rattlesnake. These lines would
complete a 230 kV loop from Rattlesnake to Bennett Mountain to Evander
Andrews and back to Rattlesnake. In addition, the Dram-Midpoint #1 230 kV
line would be looped into Rattlesnake and rebuilt to support bundled 230 kV
conductors west of Rattlesnake. Additional transmission modifications were
also modeled at DRAM substation to make the "Old Midpoint to DRAM #1"
230 kV line bypass the DRAM Substation and terminate at Boise Bench. A
230/138 kV transformer was modeled at Evander Andrews to improve system
performance under N-l conditions. Alternative #2 has no N-l outages that
produce overloads that exceeds 115 % of continuous rating and are also greater
than existing system overloads for the same N-l. Alternative #2 will require
curtailments of the proposed generators output following multiple N-
outages. As a result, Alternative #2 does not provide acceptable performance
for Network Resource Interconnection Service for the proposed unit at full
output. The Network Resource Rating for Alternative #2 is 70 MW.
Alternative #2 is anticipated to be similar in cost to Alternative #3, yet does
not perform as well.
I '
Alternative #3:Rebuild a de-energized 132 kV transmission line to 230 kV construction
between Bennett Mountain and Mora Substations. This alternative utilizes the
406 line route which passes in the vicinity of both Bennett Mountain and
Evander Andrews. The west end of the 230 kV line is assumed to terminate at
a new 230 kV Mora Substation, which is folded into the Boise Bench-
Caldwell 230 kV line. No 230/138 kV transformer is modeled to tie the two
Mora busses. A 230/138 kV transformer was modeled at Evander Andrews to
improve system performance under N-l conditions. Studies revealed the need
to reconductor/rebuild the Evander Andrews to Mountain Home Junction 138
kV line. With the previously mentioned additions in-service, two N-l outages
produce overloads above equipment continuous ratings. One overload only
requires a 2% reduction in loading to fall to a level that can be sustained
continuously. Opening another lightly loaded line can mitigate the other
overload. The estimated total cost for this alternative is approximately $26
Million, with approximately $21 Million allocated Idaho Power Company-
Power Supply for the generator interconnection improvements and the
remaining $5 Million allocated to Idaho Power Delivery to correct existing
operational concerns. Following the execution of either a Large Generator
Interconnection Agreement or an Engineering & Procurement Agreement by
Idaho Power Company - Power Supply, Idaho Power Company estimates the
time required to construct these facilities is approximately 18-21 months.
These cost estimates include direct equipment and installation labor costs, indirect labor costs
and overheads , and allowance for funds used during construction (AFUDC). A cursory
attempt has been made in this study to characterize each transmission improvement as either
needed to integrate the proposed generator" or "needed to correct existing operational
concerns . The proposed cost allocation is subject to change, as more information is known.
These are cost estimates only and final charges to the customer will be based on the actual
construction costs incurred.
Summary of Interconnection Request
A request was made to Idaho Power Co. by Idaho Power Company - Power Supply to study
the interconnection of a proposed 170/196 MW simple cycle gas turbine at the Bennett
Mountain Power Plant, near Mountain Home, Idaho, to Idaho Power s transmission system at
the 230 kV level for Network Resource Interconnection Service.
Scope of Interconnection Feasibility Study
The Interconnection Feasibility Study was done and prepared in accordance with the FERC
Order 2003-, Standard Large Generator Interconnection Procedures , to provide a preliminary
evaluation of the feasibility of the interconnection of the proposed large generating project to
the Idaho Power transmission system. This study will only be concerned with the capabilities
of the Idaho Power system to manage this new resource within the study area of the proposed
interconnection.
Description of Proposed Generating Project
Idaho Power Company - Power Supply proposes to connect a 170/196 MW simple cycle gas
turbine to the Idaho Power 230 kV transmission system, at the existing Bennett Mountain
Power Plant 2750 NE Industrial Way, Mountain Home, ill 83647. The maximum generating
capacity of the proposed unit is estimated to be 170 MW for the summer and 196 MW for
winter temperatures. The equipment is described as being a Siemens SGT6-5000F CT ECNO
Pack. The proposed commercial operation date is April 1, 2007.
Description of Existing Transmission Facilities
At the Scoping Meeting for this Interconnection Request, it was agreed that the interconnection
voltage to be studied would be 230 kV. The existing generating units at Evander Andrews Power
Complex utilize the 138 kV transmission grid. No 230 kV transmission is present at Evander
Andrews at this time.
Bennett Mountain Power Plant has four 230 kV lines in relatively close proximity. Three of them
run from the Midpoint Substation(north of Twin Falls, ill) to the east Boise area. The closest is
the Midpoint-DRAM #1 line, which is approximately 4 miles Northeast of Bennett Mountain
Power Plant. This line utilizes single 715.5 MCM conductors and has a continuous rating of 339
MV A. The Rattlesnake-Boise Bench #2 line is approximately 5 miles Northeast of Bennett
Mountain Power Plant and utilizes a 2 conductor bundle of 715.5 MCM. This line has a
continuous rating of 677 MV A. The Midpoint-Boise Bench #3 line is approximately 7 miles
Northeast of Bennett Mountain Power Plant. This line has similar conductors and the same rating
as the Rattlesnake-Boise Bench #2 line. The fourth 230 kV line terminates at Bennett Mountain
Power Plant and is the Rattlesnake-Bennett Mountain line. Rattlesnake is a relatively new
substation that folds the Midpoint to Boise Bench #2230 kV line into and out of the substation.
This line utilizes single 1272 MCM conductors and has a continuous rating of 478 MV A.
In addition to the three Midpoint to the east Boise area 230 kV lines previously mentioned, there
are two 138 kV circuits which can carry power from the Mountain Home area to the Boise Area.
They are:
Mountain Home Junction-Lucky Peak-Micron 138 kV Line
Mountain Home Junction-Evander Andrews-Strike-Swan Falls-Bowmont 138 kV
Line
Generators located in the Mountain Home area which are intended to serve load growth in the
Treasure Valley area, will be adding new incremental flows on top of existing committed east-to-
west transactions across the Midpoint West transmission cutplane. This feasibility study will
model 1100 MW of transfers across the Midpoint West cutplane, prior to this proposed generator
addition. For these studies, the flow level of the Midpoint west cutplane is defined as the sum of
the flows on the following lines:
. Midpoint-DRAM #1 230 kV line
. Midpoint-Rattlesnake #2230 kV Line
. Midpoint-Boise Bench #3230 kV Line
Lower Malad-Mountain Home Junction 138 kV Line
Upper Salmon-Mountain Home Junction 138 kV Line
Description of Configurations Studied
Since the most limiting operating conditions are expected during heavy production on the
upper and middle Snake and Boise River hydro plants , with heavy east-west transfers across
the Idaho Power transmission system, the injection of the simple cycle gas turbine s 170 MW
summer output was inserted into a power flow case that would simulate committed (1100 MW)
pre-contingency flows on the Midpoint West transmission path.
In accordance with the Scoping Meeting for this Feasibility Study Request, three alternatives
were studied, all of which employed a 230 kV interconnection voltage.
Alternative #1 employed a radial 230 kV line to connect the generator to the Midpoint-Boise
Bench #3 transmission line. The line was modeled as being 7.7 miles in length and utilized
1272 MCM single conductor construction. Additional improvements of a 230/138 kV 200
MV A transformer(duplicate of the Midpoint unit) at Rattlesnake Substation and a new 138 kV
line from Rattlesnake to Mountain Home Junction was explored to improve the performance of
this alternative.
Alternative #2 calls for the construction of two new 230 kV transmission lines from Bennett
Mountain to Evander Andrews , and Evander Andrews to Rattlesnake. These lines would
complete a 1272 MCM single conductor 230 kV loop from Rattlesnake to Bennett Mountain to
Evander Andrews and back to Rattlesnake. In addition, the Dram-Midpoint #1 230 kV line
would be looped into Rattlesnake and rebuilt to support a two conductor bundle of 715.5 MCM
conductors west of Rattlesnake. Additional transmission modifications were also modeled
outside of DRAM substation to make the "Old Midpoint to DRAM #1" 230 kV line bypass
the DRAM Substation and terminate at Boise Bench. The combination of bundled conductors
and folding the #1 line into Rattlesnake Substation necessitated the change to avoid overloads
at DRAM associated with the loss of the DRAM to Boise Bench 230 kV line. A 230/138 kV
200 MV A transformer( duplicate of the Midpoint unit) was modeled at Evander Andrews to
improve system performance under N-l conditions.
Alternative #3 employed the rebuild of a de-energized 132 kV transmission line to 230 kV
bundled 795 MCM construction between Bennett Mountain and Mora Substations. This
alternative utilizes the 406 line route (originally was the Upper Salmon to Caldwell line) which
passes in the vicinity of both Bennett Mountain and Evander Andrews. The west end of this
new 230 kV line is assumed to terminate at a new 230 kV Mora Substation, which is folded
into the Boise Bench-Caldwell 230 kV line. No 230/138 kV transformer is modeled to tie the
two Mora busses. A 230/138 kV 200 MV A transformer(duplicate of the Midpoint unit) was
modeled at Evander Andrews to improve system performance under N-l conditions. Studies
also revealed the need to reconductor/rebuild the Evander Andrews to Mountain Home
Junction 138 kV line, with this alternative.
Post-transient Study Results
This Interconnection Feasibility Study Report is for Network Resource Interconnection Service
at 230 kV, for a 170/196 MW simple cycle gas turbine at the Bennett Mountain Power Plant.
System transfers across the Midpoint West cutplane are modeled at 1100 MW prior to the
proposed transmission improvements or the proposed generator producing any power. Hydro
generation production for the Boise & Snake plants , were modeled at heavy, but realistic
levels. Ouput levels for the existing peakers at Evander Andrews and Bennett Mountain were
varied over their operating ranges as appropriate. N-O and N-l outage performance for the
existing system are recorded. As agreed in the Scoping Meeting, three alternatives were
evaluated. For each alternative, the new generator s output was taken to its summer
temperature maximum level of 170 MW and system conditions recorded for both N-O and N-
outages.
Existin2 System
The following one line diagram depicts the existing system with no outages.
MldDolnt West = 1100 MW
Existing System - No Outages
Figure 1
For the existing system, seven N-l outages produce overloads that exceed the continuous
rating of elements of the transmission system. The N-s that produce overloads with the
existing system are included in Appendix B, Figures 9-15.
Alternative #1
The following one line diagram depicts the system with Alternative #1 added, full summer
output of the generator, and with no outages.
Alternative #1 - No Outages
Figure 2
Alternative #1 has multiple N-l outages that produce overloads that exceed 115% of
continuous ratings. Some of the resulting overloads are reduced with the addition of the
Evander Andrews 230/138 kV transformer, and others are increased.
The Rattlesnake to Boise Bench #2230 kV line outage produces some of the larger overloads.
The following one line depicts a 129 % loading on the Mountain Home Junction to Lucky Peak
138 kV line, without the Rattlesnake 230/138 kV transformer.
BO SEBCH,. P"
Alternative #1- Rattlesnake-Boise Bench #2 230 kV Outage
Without the Rattlesnake 230/138 kV Transformer
Figure 3
Adding the Rattlesnake 230/138 kV Transformer to the above outage, produces a 174%
loading on the Mountain Home Junction to Lucky Peak 138 kV line.
With the Rattlesnake 230/138 kV transformer in-service, only one other N-l outage produces
overloads that exceed 115% loading and are also greater than existing system overloads for the
same N-l. That N-l is loss of the Rattlesnake3 to Boise Bench #3230 kV line.
Without the Rattlesnake 230/138 kV transformer in-service, four other N-l outages produces
overloads that exceed 115% loading and are also greater than existing system overloads for the
same N-l. They are:
Rattlesnake3 - Boise Bench #3 230 kV Line outage
Midpoint - Rattlesnake #2 230 k V line outage
Evander Andrews - Strike 138 kV line outage
Strike - Bowmont 138 kV line outage
Several other N-l outages result in overloads below 115% that would require curtailments
following the outage to get down to loadings that can be sustained continuously
Alternative #1 is an unacceptable alternative, due to the two N-l outage that produce overloads
that exceeds 115% of continuous ratings. The Network Rating for Alternative #1 is 0 MW.
Alternative #2
The following one line diagram depicts the system with Alternative #2 added, full summer
output of the generator, and with no outages.
Alternative #2 - No Outages
Figure 4
The addition of the Evander Andrews 230/138 kV transformer improves the performance of
Alternative #2 for most N-l outages, but not all. Without the Evander Andrews 230/138 kV
transformer, Alternative #2 has two N-l outages that produce overloads that exceeds 115% of
continuous rating and are greater than existing system overloads for the same N-l. With the
Evander Andrews 230/138 kV transformer, Alternative #2 has no N-l outages that produce
overloads that exceed 115% of continuous rating.
Curtailments are required for all three N-l outages of the 230 kV lines from the Mountain
Home area into Boise Bench. The following one line diagram depicts the system with
Alternative #2 added, full summer output of the generator, and the outage of the Boise Bench -
Rattlesnake #1 230 kV line.
Mid oint West = 1034
Alternative #2 - Rattlesnake-Boise Bench #1230 kV Outage
With the Proposed Unit (g) 170 MW Output
Figure 5
Loss of the Rattlesnake to Boise Bench #1 line require the proposed unit's output to be lowered
to approximately 70 MW to reduce the Boise Bench to Rattlesnake #2 overload to 100% of the
continuous rating or a level that the overload is no worse than it is for the existing system with
the same N-l outage. These contingencies and resulting system performance determines the
Network Resource Rating to be 70 MW for Alternative #2. The following one line diagram
depicts the same outage as Figure 5 above, but the output of the proposed unit has been
curtailed to 70 MW to relieve the overload on the Boise Bench to Rattlesnake #2 230 kV line.
BOISEBCHLO p"
Mid oint West = 1055
Alternative #2 - Rattlesnake-Boise Bench #1230 kV Outage
With the Proposed Unit (g) 70 MW Output
Figure 6
The loss of the Midpoint to Boise Bench #3 230 kV line requires a curtailment to lower a
118% overload of the series capacitors on the Midpoint to Rattlesnake #2 230 kV line. This
alternative does not permit the overload to be reduced by lowering the output of the proposed
unit. Lowering the output of the proposed unit will increase the overload on the series
capacitors in question. Other generators would have to be curtailed to solve this overload
scenarIo.
Alternative #2 will require curtailments of the proposed generators output following multiple
l outages. As a result, Alternative #2 does not provide acceptable performance for Network
Resource Interconnection Service for the proposed unit at full output. The Network Resource
Rating for Alternative #2 is 70 MW. Alternative #2 is also believed to very similar in cost to
Alternative #3, yet it's performance is much more problematic than Alternative #3.
Alternative #3
The following one line diagram depicts the system with Alternative #3 added, full summer
output of the generator, and with no outages.
10-
MldDolnt West = 1106 MW
,"RN;LOJ..
Alternative #3 - No Outages
Figure 7
The addition of the Evander Andrews 230/138 kV transformer improves the performance of
Alternative #3, for all but one of the N-l outages. With the Evander Andrews 230/138 kV
transformer in service, alternative #3 has no N-l outages that produce overloads that exceed
115% of continuous ratings.
Two N-l outages result in overloads below 115% and at a level that the overload is greater
than it is for the existing system with the same N-l outage. The loss of the Midpoint to Boise
Bench #3 230 kV line results in a 112% loading on the series capacitor of the Midpoint to
Rattlesnake #2230 kV line. This series capacitor is capable of 110% loading continuously, so
a 2% reduction in flow is required. Lowering generation in the Mountain Home area results in
increased flow on the series capacitor bank, so transfers across the Midpoint West cutplane
will need to be reduced to correct this overload, as well as prepare for the next contingency.
The second N-l outage that results in an overload below 115%, is the Evander Andrews to
Mora 230 kV line. This N-l outage results in a 101 % loading on the Mountain Home Junction
to Lucky Peak 138 kV line. This overload can be managed by opening the Evander Andrews
to Mountain Home Junction 138 kV line.
Alternative #3 changes the characteristics of the interconnected network enough to create the
need to reconductor/rebuild the Evander Andrews to Mountain Home Junction 138 kV line.
For the N-l outage of the Lucky Peak to Micron 138 kV line, the Evander Andrews to
Mountain Home Junction 138 kV line loads to 112% of its rating with all the peaking
generation in the Mountain Home area at full output. If the output of the peaking generation in
the Mountain Home area is reduced, the overload increases in magnitude. The following one
line diagram depicts the Lucky Peak to Micron 138 k V line outage with all the Mountain
Home area peaking generation off-line.
11-
Mld olnt West = 1157 MW
Alternative #3 - Luck Peak to Micron 138 kV Line Outage
With Peakers Off-line
Figure 8
Alternative #3 is the recommended alternative for the proposed unit at 170/196 MW for
Network Resource Interconnection Service.
Cost Allocation of Proposed Improvements
Alternative #3 contains the following five construction components:
Bennett Mountain to Mora 230 kV line
Mora 230 kV substation
Bennett Mountain substation improvements
Evander Andrews 230 kV & 138 kV substation improvements
Reconductor/rebuild of the Evander Andrews to Mountain Home Junction 138
kV line
A cursory attempt has been made in this study to characterize each transmission improvement
as either "needed to integrate the proposed generator" or "needed to correct existing
operational concerns . The costs associated with those improvements believed to be "needed
to integrate the proposed generator" are allocated to the generator interconnection. The costs
associated with those improvements believed to be "needed to correct existing operational
concerns " are allocated to IPCo Delivery.
12-
Approximate estimated costs allocated to the generator interconnection are:
$16.5 Million - Bennett Mountain to Mora 230 kV line construction costs
$ 2.6 Million - Mora 230 kV substation
$ 1.4 Million - Bennett Mountain substation improvements
$20.5 Million - Total estimated generator interconnection cost
Approximate estimated costs allocated to the IPCo Delivery are:
$ 3.5 Million - Evander Andrews 230 kV & 138 kV substation improvements
$ 1.7 Million - Evander Andrews to Mountain Home Junction 138 kV line rebuild
$ 5.2 Million - Total estimated allocation to IPCo Delivery
These cost estimates include direct equipment and installation labor costs, indirect labor costs
and overheads, and allowance for funds used during construction (AFUDC). The proposed
cost allocation is subject to change, as more information is known. These are cost estimates
only and final charges to the customer will be based on the actual construction costs incurred.
10.Short Circuit Study Results
Preliminary short circuit study results indicate the surrounding circuit breakers are believed to
be able to accommodate the increased fault duty. No circuit breaker replacements are
anticipated at this time.
11.Conclusions
The feasibility of interconnecting a 170/196 MW simple cycle gas turbine at Bennett Mountain
Power Complex to Idaho Power s 230 kV transmission system was studied. Three interconnection
alternatives were evaluated. Alternative #1 was found to be an unacceptable alternative due to
transmission system loadings that exceeded 115% for N-l outages. Alternative #2 did not provide
acceptable performance for Network Resource Interconnection Service for the proposed unit at full
output. The Network Resource Rating for Alternative #2 is 70 MW. Alternative #3 was found to
be an acceptable interconnection alternative. While Alternative #3 does require minimal
redispatch/transmission switching for one N-l outage, it is minor in nature and deemed acceptable
for this feasibility study. The estimated total cost of the transmission improvements associated with
Alternative #3 is approximately $26 Million. At this time it is believed that approximately $21
Million of these estimated costs should be allocated to the generator interconnection.
13-
, .
APPENDIX A
Method of Study
The study methodology inserts the proposed generator up to the maximum requested summer
output of 170 MW into the selected WECC power flow case and then, using the PowerWorld
Simulator powerflow program, examines the impacts of the new resource on Idaho Power
transmission system (lines, transformers, etc.) within the study area under various
operating/outage scenarios. The WECC and Idaho Power reliability criteria and Idaho Power
operating procedures were used to determine the acceptability of the alternatives considered.
The WECC case is a recent cases modified to simulate stressed but reasonable pre-contingency
energy transfers utilizing the IPC system.
Acceptability Criteria
The following acceptability criteria were used in the power flow analysis to determine the
acceptability of the alternatives:
Loadings on transmission lines and transformers should not exceed 115% of the
continuous rating, immediately flowing any N-l outage. Loading on the Midpoint 230
kV series capacitors should not exceed 135% of the continuous rating, immediately
flowing any N-l outage. These loadings levels of 115% on transmission lines and
transformers and 135% on Midpoint series capacitors correspond to IPCo s 30 minute
emergency equipment ratings. Any loadings immediately following an N-l outage
less than the 30 minute emergency rating is acceptable.
Loadings which are less than the 30 minute emergency equipment ratings, but greater
than the equipment continuous ratings , must be reduced to the continuous ratings by
generation curtailments, re-dispatch, or some other operating procedure. Any remedial
action schemes(RAS) or other transmission switching, must be judged to be reasonable
before the alternatives performance can be deemed acceptable.
The continuous rating of equipment is assumed to be the normal thermal rating of the
equipment. This rating will be as determined by the manufacturer of the equipment or
as determined by Idaho Power. Less than or equal to 100% of continuous rating for
transmission lines and transformers is acceptable. Less than or equal to 110% of
continuous rating for the Midpoint 230 kV series capacitors is acceptable.
Transmission voltages, under normal operating conditions, are maintained within plus
or minus 5% (0.05 per unit) of nominal. Therefore, voltages greater than or equal to
95 pu voltage and less than or equal to 1.05 pu voltage are acceptable.
The stable operation of the transmission system requires an adequate supply of volt-
amperes reactive (V ARs) to maintain a stable voltage profile under both steady-state
and dynamic system conditions. An inadequate supply of V ARs will result in voltage
14-
, .
decay or even collapse under the worst conditions. Idaho Power designs its system to
integrate Network Resources at full capability during specified outage conditions.
Equipment/line/path ratings used will be those that are in use at the time of the study or that are
represented by IPC upgrade projects that are either currently under construction or whose
budgets have been approved for construction in the near future. All other potential future
ratings are outside the scope of this study. Future transmission changes may, however, affect
current facility ratings used in the study.
15-
, .
APPENDIX B
l Outages That Produce Overloads On The Existing System
The following one line diagrams depict system performance following the seven N-l outages
that produce overloads which exceed the continuous rating of facilities. Figure 1 on page 5
depicts the operation of the existing system with no outages. The combination of heavy hydro
and peaker generation in the Mountain Home area, and 1100 MW east to west transfers on
Midpoint West, results in the Mountain Home Junction to Lucky Peak and Lucky Peak to
Micron 138 kV lines being loaded to 98% & 99% respectively, prior to any outages.
Mld olnt West = 981
Existing System - Midpoint to Boise Bench #3 230 kV Outage
Figure 9
16-
951
Existing System - Rattlesnake to Boise Bench #2 230 kV Outage
Figure 10
Mld olnt West.. 997
Existing System - Midpoint to Rattlesnake #2 230 kV Outage
Figure 11
17-
MldDolnt West.. 1053
Existing System - Midpoint to DRAM #1230 kV Outage
Figure 12
Mld olnt West.. 1085
Existing System - CJ Strike to Bowmont 138 kV Outage
Figure 13
18-
. '
MldDolnt West.. 1072
Existing System - Lucky Peak to Micron 138 kV Outage
Figure 14
MldDolnt West.. 1094
Existing System - Evander Andrews to CJ Strike 138 kV Outage
Figure 15
19-
, '
LARGE GENERATOR INTERCONNECTION
FEASIBILITY STUDY REPORT
for the
230 KV INTERCONNECTION OPTION
BENNETT MOUNTAIN POWER PLANT
for
Idaho Power Company - Power Supply, Interconnection Customer
for connection of
A 100/124 MW SIMPLE CYCLE GAS TURBINE PEAKING PROJECT
BENNETT MOUNTAIN POWER PLANT
IDAHO POWER COMPANY, Transmission Provider
TRANSMISSION SYSTEM
FINAL REPORT
September 30, 2005
. ,
1.0 Introduction
Idaho Power Company - Power Supply has contracted with Idaho Power Company (IPC) to
perform a Large Generator Interconnection Feasibility Study for Network Resource
Interconnection Service at 230 kV for the integration of a new 100/124 MW simple cycle gas
turbine peaking project. The proposed location is the Bennett Mountain Power Plant near
Mountain Home, Idaho.
This report documents the basis for and the results of this Feasibility Study. It describes the
proposed interconnection alternatives, the study cases used, outage scenarios assumed and
results of all work in the areas of concern.
Summary
The performance of three interconnection alternatives was evaluated to integrate a simple cycle
gas turbine with a summer rating of 100 MW and a winter rating of 124 MW, located at
Bennett Mountain Power Plant, into the Idaho Power System. Alternative #3 is the
recommended alternative.
Alternative #1:
Alternative #2:
Construct a radial 230 kV interconnection line, from a new 230 kV substation
at Bennett Mountain, to the Midpoint-Boise Bench #3 transmission line. One
l contingency results in unacceptable overloads for this alternative.
Additional Improvements , of a 230/138 kV transformer at Rattlesnake with a
new 138 kV line from Rattlesnake to Mountain Home Junction, were
evaluated in an unsuccessful attempt to achieve acceptable performance under
l outage conditions.
Construct two new 230 kV transmission lines from Bennett Mountain to
Evander Andrews and Evander Andrews to Rattlesnake. These lines would
complete a 230 kV loop from Rattlesnake to Bennett Mountain to Evander
Andrews and back to Rattlesnake. In addition, the Dram-Midpoint #1 230 kV
line would be looped into Rattlesnake and rebuilt to support bundled 230 kV
conductors west of Rattlesnake. Additional transmission modifications were
also modeled at DRAM substation to make the "Old Midpoint to DRAM #1"
230 kV line bypass the DRAM Substation and terminate at Boise Bench. A
230/138 kV transformer was modeled at Evander Andrews to improve system
performance under N-l conditions. Alternative #2 has no N-l outages that
produce overloads that exceeds 115% of continuous rating and are also greater
than existing system overloads for the same N-l. Alternative #2 will require
curtailments of the proposed generators output following multiple N-
outages. As a result, Alternative #2 does not provide acceptable performance
for Network Resource Interconnection Service for the proposed unit at full
output. The Network Resource Rating for Alternative #2 is 70 MW.
Alternative #2 is anticipated to be similar in cost to Alternative #3, yet does
not perform as well.
. .
Alternative #3:Rebuild a de-energized 132 kV transmission line to 230 kV construction
between Bennett Mountain and Mora Substations. This alternative utilizes the
406 line route which passes in the vicinity of both Bennett Mountain and
Evander Andrews. The west end of the 230 kV line is assumed to terminate at
a new 230 kV Mora Substation, which is folded into the Boise Bench-
Caldwell 230 kV line. No 230/138 kV transformer is modeled to tie the two
Mora busses. A 230/138 kV transformer was modeled at Evander Andrews to
improve system performance under N-l conditions. Studies revealed the need
to reconductor/rebuild the Evander Andrews to Mountain Home Junction 13&
kV line. With the previously mentioned additions in-service, one N-l outage
produces an overload above equipment continuous ratings. This overload
only requires a 5% reduction in loading to fall to a level that can be sustained
continuously. The estimated total cost for this alternative is approximately
$26 Million, with approximately $21 Million allocated Idaho Power Company
- Power Supply for the generator interconnection improvements and the
remaining $5 Million allocated to Idaho Power Delivery to correct existing
operational concerns. Following the execution of either a Large Generator
Interconnection Agreement or an Engineering & Procurement Agreement by
Idaho Power Company - Power Supply, Idaho Power Company estimates the
time required to construct these facilities is approximately 18-21 months.
These cost estimates include direct equipment and installation labor costs, indirect labor costs
and overheads , and allowance for funds used during construction (AFUDC). A cursory
attempt has been made in this study to characterize each transmission improvement as either
needed to integrate the proposed generator" or "needed to correct existing operational
concerns . The proposed cost allocation is subject to change, as more information is known.
These are cost estimates only and final charges to the customer will be based on the actual
construction costs incurred.
Summary of Interconnection Request
A request was made to Idaho Power Co. by Idaho Power Company - Power Supply to study
the interconnection of a proposed 100/124 MW simple cycle gas turbine at the Bennett
Mountain Power Plant, near Mountain Home, Idaho, to Idaho Power s transmission system at
the 230 kV level for Network Resource Interconnection Service.
Scope of Interconnection Feasibility Study
The Interconnection Feasibility Study was done and prepared in accordance with the FERC
Order 2003-, Standard Large Generator Interconnection Procedures, to provide a preliminary
evaluation of the feasibility of the interconnection of the proposed large generating project to
the Idaho Power transmission system. This study will only be concerned with the capabilities
of the Idaho Power system to manage this new resource within the study area of the proposed
interconnection.
. ,
Description of Proposed Generating Project
Idaho Power Company - Power Supply proposes to connect a 100/124 MW simple cycle gas
turbine to the Idaho Power 230 kV transmission system, at the existing Bennett Mountain
Power Plant, 2750 NE Industrial Way, Mountain Home, ill 83647. The maximum generating
capacity of the proposed unit is estimated to be 100 MW for the summer and 124 MW for
winter temperatures. The equipment is described as being a Siemens SSC6-3000F CT ECNO
Pack. The proposed commercial operation date is April 1, 2007.
Description of Existing Transmission Facilities
At the Scoping Meeting for this Interconnection Request, it was agreed that the interconnection
voltage to be studied would be 230 kV. The existing generating units at Evander Andrews Power
Complex utilize the 138 kV transmission grid. No 230 kV transmission is present at Evander
Andrews at this time.
Bennett Mountain Power Plant has four 230 kV lines in relatively close proximity. Three of them
run from the Midpoint Substation(north of Twin Falls, ill) to the east Boise area. The closest is
the Midpoint-DRAM #1 line, which is approximately 4 miles Northeast of Bennett Mountain
Power Plant. This line utilizes single 715.5 MCM conductors and has a continuous rating of 339
MV A. The Rattlesnake-Boise Bench #2 line is approximately 5 miles Northeast of Bennett
Mountain Power Plant and utilizes a 2 conductor bundle of 715.5 MCM. This line has a
continuous rating of 677 MV A. The Midpoint-Boise Bench #3 line is approximately 7 miles
Northeast of Bennett Mountain Power Plant. This line has similar conductors and the same rating
as the Rattlesnake-Boise Bench #2 line. The fourth 230 kV line terminates at Bennett Mountain
Power Plant and is the Rattlesnake-Bennett Mountain line. Rattlesnake is a relatively new
substation that folds the Midpoint to Boise Bench #2 230 kV line into and out of the substation.
This line utilizes single 1272 MCM conductors and has a continuous rating of 478 MVA.
In addition to the three Midpoint to the east Boise area 230 kV lines previously mentioned, there
are two 138 kV circuits which can carry power from the Mountain Home area to the Boise Area.
They are:
Mountain Home Junction-Lucky Peak-Micron 138 kV Line
Mountain Home Junction-Evander Andrews-Strike-Swan Falls-Bowmont 138 kV
Line
Generators located in the Mountain Home area which are intended to serve load growth in the
Treasure Valley area, will be adding new incremental flows on top of existing committed east-to-
west transactions across the Midpoint West transmission cutplane. This feasibility study will
model 1100 MW of transfers across the Midpoint West cutplane, prior to this proposed generator
addition. For these studies , the flow level of the Midpoint west cutplane is defined as the sum of
the flows on the following lines:
. Midpoint-DRAM #1 230 kV line
. Midpoint-Rattlesnake #2 230 kV Line
. Midpoint-Boise Bench #3 230 kV Line
Lower Malad-Mountain Home Junction 138 kV Line
Upper Salmon-Mountain Home Junction 138 kV Line
, .
Description of Configurations Studied
Since the most limiting operating conditions are expected during heavy production on the
upper and middle Snake and Boise River hydro plants , with heavy east-west transfers across
the Idaho Power transmission system, the injection of the simple cycle gas turbine s 100 MW
summer output was inserted into a power flow case that would simulate committed (1100 MW)
pre-contingency flows on the Midpoint West transmission path.
In accordance with the Scoping Meeting for this Feasibility Study Request, three alternatives
were studied, all of which employed a 230 kV interconnection voltage.
Alternative #1 employed a radial 230 kV line to connect the generator to the Midpoint-Boise
Bench #3 transmission line. The line was modeled as being 7.7 miles in length and utilized
1272 MCM single conductor construction. Additional improvements of a 230/138 kV 200
MV A transformer(duplicate of the Midpoint unit) at Rattlesnake Substation and a new 138 kV
line from Rattlesnake to Mountain Home Junction was explored to improve the performance of
this alternative.
Alternative #2 calls for the construction of two new 230 kV transmission lines from Bennett
Mountain to Evander Andrews , and Evander Andrews to Rattlesnake. These lines would
complete a 1272 MCM single conductor 230 kV loop from Rattlesnake to Bennett Mountain to
Evander Andrews and back to Rattlesnake. In addition, the Dram-Midpoint #1 230 kV line
would be looped into Rattlesnake and rebuilt to support a two conductor bundle of 715.5 MCM
conductors west of Rattlesnake. Additional transmission modifications were also modeled
outside of DRAM substation to make the "Old Midpoint to DRAM #1" 230 kV line bypass
the DRAM Substation and terminate at Boise Bench. The combination of bundled conductors
and folding the #1 line into Rattlesnake Substation necessitated the change to avoid overloads
at DRAM associated with the loss of the DRAM to Boise Bench 230 kV line. A 230/138 kV
200 MV A transformer(duplicate of the Midpoint unit) was modeled at Evander Andrews to
improve system performance under N-l conditions.
Alternative #3 employed the rebuild of a de-energized 132 kV transmission line to 230 kV
bundled 795 MCM construction between Bennett Mountain and Mora Substations. This
alternative utilizes the 406 line route (originally was the Upper Salmon to Caldwell line) which
passes in the vicinity of both Bennett Mountain and Evander Andrews. The west end of this
new 230 kV line is assumed to terminate at a new 230 kV Mora Substation, which is folded
into the Boise Bench-Caldwell 230 kV line. No 230/138 kV transformer is modeled to tie the
two Mora busses. A 230/138 kV 200 MV A transformer(duplicate of the Midpoint unit) was
modeled at Evander Andrews to improve system performance under N-l conditions. Studies
also revealed the need to reconductor/rebuild the Evander Andrews to Mountain Home
Junction 138 kV line, with this alternative.
Post-transient Study Results
This Interconnection Feasibility Study Report is for Network Resource Interconnection Service
at 230 kV, for a 100/124 MW simple cycle gas turbine at the Bennett Mountain Power Plant.
System transfers across the Midpoint West cutplane are modeled at 1100 MW prior to the
. ,
proposed transmission improvements or the proposed generator producing any power. Hydro
generation production for the Boise & Snake plants, were modeled at heavy, but realistic
levels. Ouput levels for the existing peakers at Evander Andrews and Bennett Mountain were
varied over their operating ranges as appropriate. N-O and N-l outage performance for the
existing system are recorded. As agreed in the Scoping Meeting, three alternatives were
evaluated. For each alternative, the new generator s output was taken to its summer
temperature maximum level of 100 MW and system conditions recorded for both N-O and N-
outages.
Existin2 System
The following one line diagram depicts the existing system with no outages.
Mld olnt West.. 1100
Existing System - No Outages
Figure 1
For the existing system, seven N-l outages produce overloads that exceed the continuous
rating of elements of the transmission system. The N-s that produce overloads with the
existing system are included in Appendix B, Figures 9-15.
. .
Alternative #1
The following one line diagram depicts the system with Alternative #1 added, full summer
output of the generator, and with no outages.
BO SEBCHL p"
Alternative #1 - No Outages
Figure 2
Alternative #1 has multiple N-l outages that produce overloads that exceed 115% of
continuous ratings. Some of the resulting overloads are reduced with the addition of the
Evander Andrews 230/138 kV transformer, and others are increased.
The Rattlesnake to Boise Bench #2230 kV line outage produces some of the larger overloads.
The following one line depicts a 128 % loading on the Mountain Home Junction to Lucky Peak
138 kV line, without the Rattlesnake 230/138 kV transformer.
Alternative #1- Rattlesnake-Boise Bench #2 230 kV Outage
Without the Rattlesnake 230/138 k V Transformer
Figure 3
Adding the Rattlesnake 230/138 kV Transformer to the above outage, produces a 171
loading on the Mountain Home Junction to Lucky Peak 138 kV line.
With the Rattlesnake 230/138 kV transformer in-service, no other N-l outage produces
overloads that exceed 115 % loading.
Without the Rattlesnake 230/138 kV transformer in-service, four other N-l outages produces
overloads that exceed 115% loading and are also greater than existing system overloads for the
same N-l. They are:
Rattlesnake3 - Boise Bench #3 230 kV Line outage
Midpoint - Rattlesnake #2 230 kV line outage
Evander Andrews - Strike 138 kV line outage
Strike - Bowmont 138 kV line outage
Several other N-l outages result in overloads below 115% that would require curtailments
following the outage to get down to loadings that can be sustained continuously
Alternative #1 is an unacceptable alternative, due to the N-l outage that produces overloads
that exceed 115% of continuous ratings. The Network Rating for Alternative #1 is 0 MW.
Alternative #2
The following one line diagram depicts the system with Alternative #2 added, full summer
output of the generator, and with no outages.
Mid oint West = 1100 MW
Alternative #2 - No Outages
Figure 4
The addition of the Evander Andrews 230/138 kV transformer improves the performance of
Alternative #2 for all N-l outages. Alternative #2 has no N-l outages that produce overloads
that exceed 115% of continuous rating.
Curtailments are required for all three N-l outages of the 230 kV lines from the Mountain
Home area into Boise Bench. The following one line diagram depicts the system with
Alternative #2 added, full summer output of the generator, and the outage of the Boise Bench -
Rattlesnake #1 230 kV line.
Mid oint West = 1049
Alternative #2 - Rattlesnake-Boise Bench #1230 kV Outage
With the Proposed Unit (g) 100 MW Output
Figure 5
Loss of the Rattlesnake to Boise Bench #1 line require the proposed unit's output to be lowered
to approximately 70 MW to reduce the Boise Bench to Rattlesnake #2 overload to 100% of the
continuous rating or a level that the overload is no worse than it is for the existing system with
the same N-l outage. These contingencies and resulting system performance determines the
Network Resource Rating to be 70 MW for Alternative #2. The following one line diagram
depicts the same outage as Figure 5 above, but the output of the proposed unit has been
curtailed to 70 MW to relieve the overload on the Boise Bench to Rattlesnake #2230 kV line.
Mid oint West = 1055 MW
Alternative #2 - Rattlesnake-Boise Bench #1230 kV Outage
With the Proposed Unit (g) 70 MW Output
Figure 6
The loss of the Midpoint to Boise Bench #3 230 kV line requires a curtailment to lower a
120% overload of the series capacitors on the Midpoint to Rattlesnake #2230 kV line. This
alternative does not permit the overload to be reduced by lowering the output of the proposed
unit. Lowering the output of the proposed unit will increase the overload on the series
capacitors in question. Other generators would have to be curtailed to solve this overload
scenarIO.
Alternative #2 will require curtailments of the proposed generators output following multiple
l outages. As a result, Alternative #2 does not provide acceptable performance for Network
Resource Interconnection Service for the proposed unit at full output. The Network Resource
Rating for Alternative #2 is 70 MW. Alternative #2 is also believed to very similar in cost to
Alternative #3, yet it's performance is much more problematic than Alternative #3.
10-
- ,
Alternative #3
The following one line diagram depicts the system with Alternative #3 added, full summer
output of the generator, and with no outages.
MldDolnt West .. 1117 MW
Alternative #3 - No Outages
Figure 7
The addition of the Evander Andrews 230/138 kV transformer improves the performance of
Alternative #3 , for all of the N-l outages. With the Evander Andrews 230/138 kV transformer
in service, alternative #3 has no N-l outages that produce overloads that exceed 115% of
continuous ratings.
One N-l outage results in an overload below 115% and at a level that the overload is greater
than it is for the existing system with the same N -1 outage. The loss of the Midpoint to Boise
Bench #3 230 kV line results in a 115% loading on the series capacitor of the Midpoint to
Rattlesnake #2 230 kV line. This series capacitor is capable of 110% loading continuously, so
a 5% reduction in flow is required. Lowering generation in the Mountain Home area results in
increased flow on the series capacitor bank, so transfers across the Midpoint West cutplane
will need to be reduced to correct this overload, as well as prepare for the next contingency.
Alternative #3 changes the characteristics of the interconnected network enough to create the
need to reconductor/rebuild the Evander Andrews to Mountain Home Junction 138 kV line.
For the N-l outage of the Lucky Peak to Micron 138 kV line, the Evander Andrews to
Mountain Home Junction 138 k V line loads to 114% of its rating with all the peaking
generation in the Mountain Home area at full output. If the output of the peaking generation in
the Mountain Home area is reduced, the overload increases in magnitude. The following one
line diagram depicts the Lucky Peak to Micron 138 kV line outage with all the Mountain
Home area peaking generation off-line.
11-
MldDolnt West = 1157 MW
Alternative #3 - Luck Peak to Micron 138 kV Line Outage
With Peakers Off-line
Figure 8
Alternative #3 is the recommended alternative for the proposed unit at 100/124 MW for
Network Resource Interconnection Service.
Cost Allocation of Proposed Improvements
Alternative #3 contains the following five construction components:
Bennett Mountain to Mora 230 kV line
Mora 230 kV substation
Bennett Mountain substation improvements
Evander Andrews 230 kV & 138 kV substation improvements
Reconductor/rebuild of the Evander Andrews to Mountain Home Junction 138
kV line
A cursory attempt has been made in this study to characterize each transmission improvement
as either "needed to integrate the proposed generator" or "needed to correct existing
operational concerns . The costs associated with those improvements believed to be "needed
to integrate the proposed generator" are allocated to the generator interconnection. The costs
associated with those improvements believed to be "needed to correct existing operational
concerns " are allocated to IPCo Delivery.
12-
Approximate estimated costs allocated to the generator interconnection are:
$16.5 Million - Bennett Mountain to Mora 230 kV line construction costs
$ 2.6 Million - Mora 230 kV substation
$ 1.4 Million - Bennett Mountain substation improvements
$20.5 Million - Total estimated generator interconnection cost
Approximate estimated costs allocated to the IPCo Delivery are:
$ 3.5 Million - Evander Andrews 230 kV & 138 kV substation improvements
$ 1.7 Million - Evander Andrews to Mountain Home Junction 138 kV line rebuild
$ 5.2 Million - Total estimated allocation to IPCo Delivery
These cost estimates include direct equipment and installation labor costs , indirect labor costs
and overheads , and allowance for funds used during construction (AFUDC). The proposed
cost allocation is subject to change, as more information is known. These are cost estimates
only and final charges to the customer will be based on the actual construction costs incurred.
10.Short Circuit Study Results
Preliminary short circuit study results indicate the surrounding circuit breakers are believed to
be able to accommodate the increased fault duty. No circuit breaker replacements are
anticipated at this time.
11.Conclusions
The feasibility of interconnecting a 100/124 MW simple cycle gas turbine at Bennett Mountain
Power Complex to Idaho Power s 230 kV transmission system was studied. Three interconnection
alternatives were evaluated. Alternative #1 was found to be an unacceptable alternative due to
transmission system loadings that exceeded 115% for a N-l outage. Alternative #2 did not provide
acceptable performance for Network Resource Interconnection Service for the proposed unit at full
output. The Network Resource Rating for Alternative #2 is 70 MW. Alternative #3 was found to
be an acceptable interconnection alternative. While Alternative #3 does require minimal
redispatch/transmission switching for one N-l outage, it is minor in nature and deemed acceptable
for this feasibility study. The estimated total cost of the transmission improvements associated with
Alternative #3 is approximately $26 Million. At this time it is believed that approximately $21
Million of these estimated costs should be allocated to the generator interconnection.
13-
APPENDIX A
1.0 Method of Study
The study methodology inserts the proposed generator up to the maximum requested summer
output of 100 MW into the selected WECC power flow case and then, using the PowerWorld
Simulator powerflow program, examines the impacts of the new resource on Idaho Power
transmission system (lines, transformers, etc.) within the study area under various
operating/outage scenarios. The WECC and Idaho Power reliability criteria and Idaho Power
operating procedures were used to determine the acceptability of the alternatives considered.
The WECC case is a recent cases modified to simulate stressed but reasonable pre-contingency
energy transfers utilizing the IPC system.
Acceptability Criteria
The following acceptability criteria were used in the power flow analysis to determine the
acceptability of the alternatives:
Loadings on transmission lines and transformers should not exceed 115% of the
continuous rating, immediately flowing any N-l outage. Loading on the Midpoint 230
kV series capacitors should not exceed 135% of the continuous rating, immediately
flowing any N-l outage. These loadings levels of 115% on transmission lines and
transformers and 135% on Midpoint series capacitors correspond to IPCo s 30 minute
emergency equipment ratings. Any loadings immediately following an N-l outage
less than the 30 minute emergency rating is acceptable.
Loadings which are less than the 30 minute emergency equipment ratings, but greater
than the equipment continuous ratings , must be reduced to the continuous ratings by
generation curtailments, re-dispatch, or some other operating procedure. Any remedial
action schemes(RAS) or other transmission switching, must be judged to be reasonable
before the alternatives performance can be deemed acceptable.
The continuous rating of equipment is assumed to be the normal thermal rating of the
eq:uipment. This rating will be as determined by the manufacturer of the equipment or
as determined by Idaho Power. Less than or equal to 100% of continuous rating for
transmission lines and transformers is acceptable. Less than or equal to 110% of
continuous rating for the Midpoint 230 kV series capacitors is acceptable.
Transmission voltages, under normal operating conditions , are maintained within plus
or minus 5% (0.05 per unit) of nominal. Therefore, voltages greater than or equal to
95 pu voltage and less than or equal to 1.05 pu voltage are acceptable.
The stable operation of the transmission system requires an adequate supply of volt-
amperes reactive (V ARs) to maintain a stable voltage profile under both steady-state
and dynamic system conditions. An inadequate supply of V ARs will result in voltage
14-
decay or even collapse under the worst conditions. Idaho Power designs its system to
integrate Network Resources at full capability during specified outage conditions.
Equipment/line/path ratings used will be those that are in use at the time of the study or that are
represented by IPC upgrade projects that are either currently under construction or whose
budgets have been approved for construction in the near future. All other potential future
ratings are outside the scope of this study. Future transmission changes may, however, affect
current facility ratings used in the study.
15-
. I
APPENDIX B
1.0 l Outages That Produce Overloads On The Existing System
The following one line diagrams depict system performance following the seven N-l outages
that produce overloads which exceed the continuous rating of facilities. Figure 1 on page 5
depicts the operation of the existing system with no outages. The combination of heavy hydro
and peaker generation in the Mountain Home area, and 1100 MW east to west transfers on
Midpoint West, results in the Mountain Home Junction to Lucky Peak and Lucky Peak to
Micron 138 kV lines being loaded to 98% & 99% respectively, prior to any outages.
Mld olnt West.. 981
Existing System - Midpoint to Boise Bench #3 230 kV Outage
Figure 9
16-
Mld olnt West.. 951
Existing System - Rattlesnake to Boise Bench #2 230 k V Outage
Figure 10
Mld olnt West. 997
Existing System - Midpoint to Rattlesnake #2 230 kV Outage
Figure 11
17-
, .
MldDolnt West.. 1053
Existing System - Midpoint to DRAM #1230 kV Outage
Figure 12
Mld olnt West.. 1085
Existing System - CJ Strike to Bowmont 138 kV Outage
Figure 13
18-
, .
Mld olnt West .. 1072
Existing System - Lucky Peak to Micron 138 kV Outage
Figure 14
Mld olnt West. 1094
Existing System - Evander Andrews to CJ Strike 138 kV Outage
Figure 15
19-
.;,. .
LARGE GENERA TOR INTERCONNECTION
FEASIBILITY STUDY REPORT
for the
230 KV INTERCONNECTION OPTION
BENNETT MOUNTAIN POWER PLANT
for
Idaho Power Company - Power Supply, Interconnection Customer
for connection of
A 91/99 MW SIMPLE CYCLE GAS TURBINE PEAKING PROJECT
BENNETT MOUNTAIN POWER PLANT
IDAHO POWER COMPANY, Transmission Provider
TRANSMISSION SYSTEM
FINAL REPORT
September 30, 2005
Introduction
Idaho Power Company - Power Supply has contracted with Idaho Power Company (IPC) to
perform a Large Generator Interconnection Feasibility Study for Network Resource
Interconnection Service at 230 kV for the integration of a new 91/99 MW simple cycle gas
turbine peaking project. The proposed location is the Bennett Mountain Power Plant near
Mountain Home, Idaho.
This report documents the basis for and the results of this Feasibility Study. It describes the
proposed interconnection alternatives, the study cases used, outage scenarios assumed and
results of all work in the areas of concern.
Summary
The performance of three interconnection alternatives was evaluated to integrate a simple cycle
gas turbine with a summer rating of 91 MW and a winter rating of 99 MW, located at Bennett
Mountain Power Plant, into the Idaho Power System. Alternative #3 is the recommended
alternative.
Alternative #1:
Alternative #2:
Construct a radial 230 kV interconnection line, from a new 230 kV substation
at Bennett Mountain, to the Midpoint-Boise Bench #3 transmission line. One
l contingency results in unacceptable overloads for this alternative.
Additional improvements, of a 230/138 kV transformer at Rattlesnake with a
new 138 kV line from Rattlesnake to Mountain Home Junction, were
evaluated in an unsuccessful attempt to achieve acceptable performance under
l outage conditions.
Construct two new 230 kV transmission lines from Bennett Mountain to
Evander Andrews and Evander Andrews to Rattlesnake. These lines would
complete a 230 kV loop from Rattlesnake to Bennett Mountain to Evander
Andrews and back to Rattlesnake. In addition, the Dram-Midpoint #1230 kV
line would be looped into Rattlesnake and rebuilt to support bundled 230 kV
conductors west of Rattlesnake. Additional transmission modifications were
also modeled at DRAM substation to make the "Old Midpoint to DRAM #1"
230 kV line bypass the DRAM Substation and terminate at Boise Bench. A
230/138 kV transformer was modeled at Evander Andrews to improve system
performance under N-l conditions. Alternative #2 has no N-l outages that
produce overloads that exceed 115% of continuous rating and are also greater
than existing system overloads for the same N-l. Alternative #2 will require
curtailments of the proposed generators output following multiple N-
outages. As a result, Alternative #2 does not provide acceptable performance
for Network Resource Interconnection Service for the proposed unit at full
output. The Network Resource Rating for Alternative #2 is 70 MW.
Alternative #2 is anticipated to be similar in cost to Alternative #3 , yet does
not perform as well.
Alternative #3:Rebuild a de-energized 132 kV transmission line to 230 kV construction
between Bennett Mountain and Mora Substations. This alternative utilizes the
406 line route which passes in the vicinity of both Bennett Mountain and
Evander Andrews. The west end of the 230 kV line is assumed to terminate at
a new 230 kV Mora Substation, which is folded into the Boise Bench-
Caldwell 230 kV line. No 230/138 kV transformer is modeled to tie the two
Mora busses. A 230/138 kV transformer was modeled at Evander Andrews to
improve system performance under N-l conditions. Studies revealed the need
to reconductor/rebuild the Evander Andrews to Mountain Home Junction 138
kV line. With the previously mentioned additions in-service, one N-l outage
produces an overload above equipment continuous ratings. This overload
only requires a 6% reduction in loading to fall to a level that can be sustained
continuously. The estimated total cost for this alternative is approximately
$26 Million, with approximately $21 Million allocated Idaho Power Company
- Power Supply for the generator interconnection improvements and the
remaining $5 Million allocated to Idaho Power Delivery to correct existing
operational concerns. Following the execution of either a Large Generator
Interconnection Agreement or an Engineering & Procurement Agreement by
Idaho Power Company - Power Supply, Idaho Power Company estimates the
time required to construct these facilities is approximately 18-21 months.
These cost estimates include direct equipment and installation labor costs, indirect labor costs
and overheads , and allowance for funds used during construction (AFUDC). A cursory
attempt has been made in this study to characterize each transmission improvement as either
needed to integrate the proposed generator" or "needed to correct existing operational
concerns . The proposed cost allocation is subject to change, as more information is known.
These are cost estimates only and final charges to the customer will be based on the actual
construction costs incurred.
Summary of Interconnection Request
A request was made to Idaho Power Co. by Idaho Power Company - Power Supply to study
the interconnection of a proposed 91/99 MW simple cycle gas turbine at the Bennett Mountain
Power Plant, near Mountain Home, Idaho, to Idaho Power s transmission system at the 230 kV
level for Network Resource Interconnection Service.
Scope of Interconnection Feasibility Study
The Interconnection Feasibility Study was done and prepared in accordance withthe FERC
Order 2003-, Standard Large Generator Interconnection Procedures, to provide a preliminary
evaluation of the feasibility of the interconnection of the proposed large generating project to
the Idaho Power transmission system. This study will only be concerned with the capabilities
of the Idaho Power system to manage this new resource within the study area of the proposed
interconnection.
Description of Proposed Generating Project
Idaho Power Company - Power Supply proposes to connect a 91/99 MW simple cycle gas
turbine to the Idaho Power 230 kV transmission system, at the existing Bennett Mountain
Power Plant, 2750 NE Industrial Way, Mountain Home, ill 83647. The maximum generating
capacity of the proposed unit is estimated to be 91 MW for the summer and 99 MW for winter
temperatures. The equipment is described as being a GE LMS 100 Package or two LM6000
Packages. The proposed commercial operation date is April 1 , 2007.
Description of Existing Transmission Facilities
At the Scoping Meeting for this Interconnection Request, it was agreed that the interconnection
voltage to be studied would be 230 kV. The existing generating units at Evander Andrews Power
Complex utilize the 138 kV transmission grid. No 230 kV transmission is present at Evander
Andrews at this time.
Bennett Mountain Power Plant has four 230 kV lines in relatively close proximity. Three of them
run from the Midpoint Substation(north of Twin Falls , ill) to the east Boise area. The closest is
the Midpoint-DRAM #1 line, which is approximately 4 miles Northeast of Bennett Mountain
Power Plant. This line utilizes single 715.5 MCM conductors and has a continuous rating of 339
MV A. The Rattlesnake-Boise Bench #2 line is approximately 5 miles Northeast of Bennett
Mountain Power Plant and utilizes a 2 conductor bundle of 715.5 MCM. This line has a
continuous rating of 677 MV A. The Midpoint-Boise Bench #3 line is approximately 7 miles
Northeast of Bennett Mountain Power Plant. This line has similar conductors and the same rating
as the Rattlesnake-Boise Bench #2 line. The fourth 230 kV line terminates at Bennett Mountain
Power Plant and is the Rattlesnake-Bennett Mountain line. Rattlesnake is a relatively new
substation that folds the Midpoint to Boise Bench #2 230 kV line into and out of the substation.
This line utilizes single 1272 MCM conductors and has a continuous rating of 478 MV
In addition to the three Midpoint to the east Boise area 230 kV lines previously mentioned, there
are two 138 kV circuits which can carry power from the Mountain Home area to the Boise Area.
They are:
Mountain Home Junction-Lucky Peak-Micron 138 kV Line
Mountain Home Junction-Evander Andrews-Strike-Swan Falls-Bowmont 138 kV
Line
Generators located in the Mountain Home area which are intended to serve load growth in the
Treasure Valley area, will be adding new incremental flows on top of existing committed east-to-
west transactions across the Midpoint West transmission cutplane. This feasibility study will
model 1100 MW of transfers across the Midpoint West cutplane, prior to this proposed generator
addition. For these studies , the flow level of the Midpoint west cutplane is defined as the sum of
the flows on the following lines:
. Midpoint-DRAM #1 230 kV line
. Midpoint-Rattlesnake #2230 kV Line
. Midpoint-Boise Bench #3230 kV Line
Lower Malad-Mountain Home Junction 138 kV Line
Upper Salmon-Mountain Home Junction 138 kV Line
Description of Configurations Studied
Since the most limiting operating conditions are expected during heavy production on the
upper and middle Snake and Boise River hydro plants, with heavy east-west transfers across
the Idaho Power transmission system, the injection of the simple cycle gas turbine s 91 MW
summer output was inserted into a power flow case that would simulate committed (1100 MW)
pre-contingency flows on the Midpoint West transmission path.
In accordance with the Scoping Meeting for this Feasibility Study Request, three alternatives
were studied, all of which employed a 230 kV interconnection voltage.
Alternative #1 employed a radial 230 kV line to connect the generator to the Midpoint-Boise
Bench #3 transmission line. The line was modeled as being 7.7 miles in length and utilized
1272 MCM single conductor construction. Additional improvements of a 230/138 kV 200
MV A transformer(duplicate of the Midpoint unit) at Rattlesnake Substation and a new 138 kV
line from Rattlesnake to Mountain Home Junction was explored to improve the performance of
this alternative.
Alternative #2 calls for the construction of two new 230 kV transmission lines from Bennett
Mountain to Evander Andrews, and Evander Andrews to Rattlesnake. These lines would
complete a 1272 MCM single conductor 230 kV loop from Rattlesnake to Bennett Mountain to
Evander Andrews and back to Rattlesnake. In addition, the Dram-Midpoint #1 230 kV line
would be looped into Rattlesnake and rebuilt to support a two conductor bundle of 715.5 MCM
conductors west of Rattlesnake. Additional transmission modifications were also modeled
outside of DRAM substation to make the "Old Midpoint to DRAM #1" 230 kV line bypass
the DRAM Substation and terminate at Boise Bench. The combination of bundled conductors
and folding the #1 line into Rattlesnake Substation necessitated the change to avoid overloads
at DRAM associated with the loss of the DRAM to Boise Bench 230 kV line. A 230/138 kV
200 MV A transformer(duplicate of the Midpoint unit) was modeled at Evander Andrews to
improve system performance under N-l conditions.
Alternative #3 employed the rebuild of a de-energized 132 kV transmission line to 230 kV
bundled 795 MCM construction between Bennett Mountain and Mora Substations. This
alternative utilizes the 406 line route (originally was the Upper Salmon to Caldwell line) which
passes in the vicinity of both Bennett Mountain and Evander Andrews. The west end of this
new 230 kV line is assumed to terminate at a new 230 kV Mora Substation, which is folded
into the Boise Bench-Caldwell 230 kV line. No 230/138 kV transformer is modeled to tie the
two Mora busses. A 230/138 kV 200 MV A transformer(duplicate of the Midpoint unit) was
modeled at Evander Andrews to improve system performance under N-l conditions. Studies
also revealed the need to reconductor/rebuild the Evander Andrews to Mountain Home
Junction 138 kV line, with this alternative.
Post-transient Study Results
This Interconnection Feasibility Study Report is for Network Resource Interconnection Service
at 230 kV, for a 91/99 MW simple cycle gas turbine at the Bennett Mountain Power Plant.
System transfers across the Midpoint West cutplane are modeled at 1100 MW prior to the
proposed transmission improvements or the proposed generator producing any power. Hydro
generation production for the Boise & Snake plants, were modeled at heavy, but realistic
levels. Ouput levels for the existing peakers at Evander Andrews and Bennett Mountain were
varied over their operating ranges as appropriate. N-O and N-l outage performance for the
existing system are recorded. As agreed in the Scoping Meeting, three alternatives were
evaluated. For each alternative, the new generator s output was taken to its summer
temperature maximum level of 91 MW and system conditions recorded for both N-O and N-
outages.
Existin2 System
The following one line diagram depicts the existing system with no outages.
MldDolnt West'" 1100 MW
Existing System - No Outages
Figure 1
For the existing system, seven N-l outages produce overloads that exceed the continuous
rating of elements of the transmission system. The N-l' s that produce overloads with the
existing system are included in Appendix B , Figures 9-15.
Alternative #1
The following one line diagram depicts the system with Alternative #1 added, full summer
output of the generator, and with no outages.
BOISEBCH1. P"
Mid oint West = 1079 MW
MIOLOC31 MIDPOINT00p" 1.O1p"
Alternative #1- No Outages
Figure 2
Alternative #1 has multiple N-l outages that produce overloads that exceed 115% of
continuous ratings. Some of the resulting overloads are reduced with the addition of the
Evander Andrews 230/138 kV transformer, and others are increased.
The Rattlesnake to Boise Bench #2230 kV line outage produces some of the larger overloads.
The following one line depicts a 128 % loading on the Mountain Home Junction to Lucky Peak
138 kV line, without the Rattlesnake 230/138 kV transformer.
nl"J',
Alternative #1- Rattlesnake-Boise Bench #2 230 kV Outage
Without the Rattlesnake 230/138 k V Transformer
Figure 3
Adding the Rattlesnake 230/138 kV Transformer to the above outage, produces a 171
loading on the Mountain Home Junction to Lucky Peak 138 k V line.
With the Rattlesnake 230/138 kV transformer in-service, no other N-l outage produces
overloads that exceed 115% loading.
Without the Rattlesnake 230/138 kV transformer in-service, four other N-l outages produces
overloads that exceed 115% loading and are also greater than existing system overloads for the
same N-1. They are:
Rattlesnake3 - Boise Bench #3230 kV Line outage
Midpoint - Rattlesnake #2 230 kV line outage
Evander Andrews - Strike 138 kV line outage
Strike - Bowmont 138 kV line outage
Several other N-l outages result in overloads below 115% that would require curtailments
following the outage to get down to loadings that can be sustained continuously
Alternative #1 is an unacceptable alternative, due to the N-l outage that produces overloads
that exceed 115% of continuous ratings. The Network Rating for Alternative #1 is 0 MW.
Alternative #2
The following one line diagram depicts the system with Alternative #2 added, full summer
output of the generator, and with no outages.
Mid oint West = 1102 MW
Alternative #2 - No Outages
Figure 4
The addition of the Evander Andrews 230/138 kV transformer improves the performance of
Alternative #2 for all N-l outages. Alternative #2 has no N-l outages that produce overloads
that exceed 115 % of continuous rating.
Curtailments are required for all three N-l outages of the 230 kV lines from the Mountain
Home area into Boise Bench. The following one line diagram depicts the system with
Alternative #2 added, full summer output of the generator, and the outage of the Boise Bench -
Rattlesnake #1 230 kV line.
Mid oint West = 1051
Alternative #2 - Rattlesnake-Boise Bench #1230 kV Outage
With the Proposed Unit (g) 91 MW Output
Figure 5
Loss of the Rattlesnake to Boise Bench #1 line require the proposed unit's output to be lowered
to approximately 70 MW to reduce the Boise Bench to Rattlesnake #2 overload to 100% of the
continuous rating or a level that the overload is no worse than it is for the existing system with
the same N-l outage. These contingencies and resulting system performance determines the
Network Resource Rating to be 70 MW for Alternative #2. The following one line diagram
depicts the same outage as Figure 5 above, but the output of the proposed unit has been
curtailed to 70 MW to relieve the overload on the Boise Bench to Rattlesnake #2230 kV line.
Mid oint West = 1055
Alternative #2 - Rattlesnake-Boise Bench #1230 kV Outage
With the Proposed Unit (g) 70 MW Output
Figure 6
The loss of the Midpoint to Boise Bench #3 230 kV line requires a curtailment to lower a
120% overload of the series capacitors on the Midpoint to Rattlesnake #2230 kV line. This
alternative does not permit the overload to be reduced by lowering the output of the proposed
unit. Lowering the output of the proposed unit will increase the overload on the series
capacitors in question. Other generators would have to be curtailed to solve this overload
scenarIo.
Alternative #2 will require curtailments of the proposed generators output following multiple
loutages. As a result, Alternative #2 does not provide acceptable performance for Network
Resource Interconnection Service for the proposed unit at full output. The Network Resource
Rating for Alternative #2 is 70 MW. Alternative #2 is also believed to very similar in cost to
Alternative #3 , yet it's performance is much more problematic than Alternative #3.
10-
Alternative #3
The following one line diagram depicts the system with Alternative #3 added, full summer
output of the generator, and with no outages.
'OISEBCHUI',",
MldDolnt West.. 1118 MW
Alternative #3 - No Outages
Figure 7
The addition of the Evander Andrews 230/138 kV transformer improves the performance of
Alternative #3 , for all of the N-l outages. With the Evander Andrews 230/138 kV transformer
in service, alternative #3 has no N-l outages that produce overloads that exceed 115% of
continuous ratings.
One N-l outage results in an overload below 115% and at a level that the overload is greater
than it is for the existing system with the same N-l outage. The loss of the Midpoint to Boise
Bench #3 230 kV line results in a 116% loading on the series capacitor of the Midpoint to
Rattlesnake #2230 kV line. This series capacitor is capable of 110% loading continuously, so
a 6% reduction in flow is required. Lowering generation in the Mountain Home area results in
increased flow on the series capacitor bank, so transfers across the Midpoint West cutplane
will need to be reduced to correct this overload, as well as prepare for the next contingency.
Alternative #3 changes the characteristics of the interconnected network enough to create the
need to reconductor/rebuild the Evander Andrews to Mountain Home Junction 138 kV line.
For the N-l outage of the Lucky Peak to Micron 138 kV line, the Evander Andrews to
Mountain Home Junction 138 kV line loads to 114% of its rating with all the peaking
generation in the Mountain Home area at full output. If the output of the peaking generation in
the Mountain Home area is reduced, the overload increases in magnitude. The following one
line diagram depicts the Lucky Peak to Micron 138 kV line outage with all the Mountain
Home area peaking generation off-line.
11-
LARGE GENERA TOR INTERCONNECTION
FEASIBILITY STUDY REPORT
for the
230 KV INTERCONNECTION OPTION
BENNETT MOUNTAIN POWER PLANT
for
Idaho Power Company - Power Supply, Interconnection Customer
for connection of
A 91/99 MW SIMPLE CYCLE GAS TURBINE PEAKING PROJECT
BENNETT MOUNTAIN POWER PLANT
IDAHO POWER COMPANY, Transmission Provider
TRANSMISSION SYSTEM
FINAL REPORT
September 30, 2005
Introduction
Idaho Power Company - Power Supply has contracted with Idaho Power Company (IPC) to
perform a Large Generator Interconnection Feasibility Study for Network Resource
Interconnection Service at 230 kV for the integration of a new 91/99 MW simple cycle gas
turbine peaking project. The proposed location is the Bennett Mountain Power Plant near
Mountain Home, Idaho.
This report documents the basis for and the results of this Feasibility Study. It describes the
proposed interconnection alternatives, the study cases used, outage scenarios assumed and
results of all work in the areas of concern.
Summary
The performance of three interconnection alternatives was evaluated to integrate a simple cycle
gas turbine with a summer rating of 91 MW and a winter rating of 99 MW, located at Bennett
Mountain Power Plant, into the Idaho Power System. Alternative #3 is the recommended
alternative.
Alternative #1:
Alternative #2:
Construct a radial 230 kV interconnection line, from a new 230 kV substation
at Bennett Mountain, to the Midpoint-Boise Bench #3 transmission line. One
l contingency results in unacceptable overloads for this alternative.
Additional improvements , of a 230/138 kV transformer at Rattlesnake with a
new 138 kV line from Rattlesnake to Mountain Home Junction, were
evaluated in an unsuccessful attempt to achieve acceptable performance under
l outage conditions.
Construct two new 230 kV transmission lines from Bennett Mountain to
Evander Andrews and Evander Andrews to Rattlesnake. These lines would
complete a 230 kV loop from Rattlesnake to Bennett Mountain to Evander
Andrews and back to Rattlesnake. In addition, the Dram-Midpoint #1 230 kV
line would be looped into Rattlesnake and rebuilt to support bundled 230 kV
conductors west of Rattlesnake. Additional transmission modifications were
also modeled at DRAM substation to make the "Old Midpoint to DRAM #1"
230 kV line bypass the DRAM Substation and terminate at Boise Bench.
230/138 kV transformer was modeled at Evander Andrews to improve system
performance under N-l conditions. Alternative #2 has no N-l outages that
produce overloads that exceed 115% of continuous rating and are also greater
than existing system overloads for the same N-l. Alternative #2 will require
curtailments of the proposed generators output following multiple N-
outages. As a result, Alternative #2 does not provide acceptable performance
for Network Resource Interconnection Service for the proposed unit at full
output. The Network Resource Rating for Alternative #2 is 70 MW.
Alternative #2 is anticipated to be similar in cost to Alternative #3, yet does
not perform as well.
Alternative #3:Rebuild a de-energized 132 kV transmission line to 230 kV construction
between Bennett Mountain and Mora Substations. This alternative utilizes the
406 line route which passes in the vicinity of both Bennett Mountain and
Evander Andrews. The west end of the 230 kV line is assumed to terminate at
a new 230 kV Mora Substation, which is folded into the Boise Bench-
Caldwell 230 kV line. No 230/138 kV transformer is modeled to tie the two
Mora busses. A 230/138 kV transformer was modeled at Evander Andrews to
improve system performance under N-l conditions. Studies revealed the need
to reconductor/rebuild the Evander Andrews to Mountain Home Junction 138
kV line. With the previously mentioned additions in-service, one N-l outage
produces an overload above equipment continuous ratings. This overload
only requires a 6% reduction in loading to fall to a level that can be sustained
continuously. The estimated total cost for this alternative is approximately
$26 Million, with approximately $21 Million allocated Idaho Power Company
- Power Supply for the generator interconnection improvements and the
remaining $5 Million allocated to Idaho Power Delivery to correct existing
operational concerns. Following the execution of either a Large Generator
Interconnection Agreement or an Engineering & Procurement Agreement by
Idaho Power Company - Power Supply, Idaho Power Company estimates the
time required to construct these facilities is approximately 18-21 months.
These cost estimates include direct equipment and installation labor costs, indirect labor costs
and overheads, and allowance for funds used during construction (AFUDC). A cursory
attempt has been made in this study to characterize each transmission improvement as either
needed to integrate the proposed generator" or "needed to correct existing operational
concerns . The proposed cost allocation is subject to change, as more information is known.
These are cost estimates only and final charges to the customer will be based on the actual
construction costs incurred.
Summary of Interconnection Request
A request was made to Idaho Power Co. by Idaho Power Company - Power Supply to study
the interconnection of a proposed 91/99 MW simple cycle gas turbine at the Bennett Mountain
Power Plant, near Mountain Home, Idaho, to Idaho Power s transmission system at the 230 kV
level for Network Resource Interconnection Service.
Scope of Interconnection Feasibility Study
The Interconnection Feasibility Study was done and prepared in accordance with the FERC
Order 20m-, Standard Large Generator Interconnection Procedures, to provide a preliminary
evaluation of the feasibility of the interconnection of the proposed large generating project to
the Idaho Power transmission system. This study will only be concerned with the capabilities
of the Idaho Power system to manage this new resource within the study area of the proposed
interconnection.
Description of Proposed Generating Project
Idaho Power Company - Power Supply proposes to connect a 91/99 MW simple cycle gas
turbine to the Idaho Power 230 kV transmission system, at the existing Bennett Mountain
Power Plant, 2750 NE Industrial Way, Mountain Home, ill 83647. The maximum generating
capacity of the proposed unit is estimated to be 91 MW for the summer and 99 MW for winter
temperatures. The equipment is described as being aGE LMS 100 Package or two LM6000
Packages. The proposed commercial operation date is April 1 , 2007.
Description of Existing Transmission Facilities
At the Scoping Meeting for this Interconnection Request, it was agreed that the interconnection
voltage to be studied would be 230 kV. The existing generating units at Evander Andrews Power
Complex utilize the 138 kV transmission grid. No 230 kV transmission is present at Evander
Andrews at this time.
Bennett Mountain Power Plant has four 230 kV lines in relatively close proximity. Three of them
run from the Midpoint Substation(north of Twin Falls, ill) to the east Boise area. The closest is
the Midpoint-DRAM #1 line, which is approximately 4 miles Northeast of Bennett Mountain
Power Plant. This line utilizes single 715.5 MCM conductors and has a continuous rating of 339
MV A. The Rattlesnake-Boise Bench #2 line is approximately 5 miles Northeast of Bennett
Mountain Power Plant and utilizes a 2 conductor bundle of 715.5 MCM. This line has a
continuous rating of 677 MV A. The Midpoint-Boise Bench #3 line is approximately 7 miles
Northeast of Bennett Mountain Power Plant. This line has similar conductors and the same rating
as the Rattlesnake-Boise Bench #2 line. The fourth 230 kV line terminates at Bennett Mountain
Power Plant and is the Rattlesnake-Bennett Mountain line. Rattlesnake is a relatively new
substation that folds the Midpoint to Boise Bench #2 230 kV line into and out of the substation.
This line utilizes single 1272 MCM conductors and has a continuous rating of 478 MV
In addition to the three Midpoint to the east Boise area 230 kV lines previously mentioned, there
are two 138 kV circuits which can carry power from the Mountain Home area to the Boise Area.
They are:
Mountain Home Junction-Lucky Peak-Micron 138 kV Line
Mountain Home Junction-Evander Andrews-Strike-Swan Falls-Bowmont 138 kV
Line
Generators located in the Mountain Home area which are intended to serve load growth in the
Treasure Valley area, will be adding new incremental flows on top of existing committed east-to-
west transactions across the Midpoint West transmission cutplane. This feasibility study will
model 1100 MW of transfers across the Midpoint West cutplane, prior to this proposed generator
addition. For these studies , the flow level of the Midpoint west cutplane is defined as the sum of
the flows on the following lines:
. Midpoint-DRAM #1 230 kV line
. Midpoint-Rattlesnake #2 230 kV Line
. Midpoint-Boise Bench #3 230 kV Line
Lower Malad-Mountain Home Junction 138 kV Line
Upper Salmon-Mountain Home Junction 138 kV Line
Description of Configurations Studied
Since the most limiting operating conditions are expected during heavy production on the
upper and middle Snake and Boise River hydro plants, with heavy east-west transfers across
the Idaho Power transmission system, the injection of the simple cycle gas turbine s 91 MW
summer output was inserted into a power flow case that would simulate committed (1100 MW)
pre-contingency flows on the Midpoint West transmission path.
In accordance with the Scoping Meeting for this Feasibility Study Request, three alternatives
were studied, all of which employed a 230 kV interconnection voltage.
Alternative #1 employed a radial 230 kV line to connect the generator to the Midpoint-Boise
Bench #3 transmission line. The line was modeled as being 7.7 miles in length and utilized
1272 MCM single conductor construction. Additional improvements of a 230/138 kV 200
MV A transformer(duplicate of the Midpoint unit) at Rattlesnake Substation and a new 138 kV
line from Rattlesnake to Mountain Home Junction was explored to improve the performance of
this alternative.
Alternative #2 calls for the construction of two new 230 kV transmission lines from Bennett
Mountain to Evander Andrews, and Evander Andrews to Rattlesnake. These lines would
complete a 1272 MCM single conductor 230 kV loop from Rattlesnake to Bennett Mountain to
Evander Andrews and back to Rattlesnake. In addition, the Dram-Midpoint #1 230 kV line
would be looped into Rattlesnake and rebuilt to support a two conductor bundle of 715.5 MCM
conductors west of Rattlesnake. Additional transmission modifications were also modeled
outside of DRAM substation to make the "Old Midpoint to DRAM #1" 230 kV line bypass
the DRAM Substation and terminate at Boise Bench. The combination of bundled conductors
and folding the #1 line into Rattlesnake Substation necessitated the change to avoid overloads
at DRAM associated with the loss of the DRAM to Boise Bench 230 kV line. A 230/138 kV
200 MV A transformer(duplicate of the Midpoint unit) was modeled at Evander Andrews to
improve system performance under N-l conditions.
Alternative #3 employed the rebuild of a de-energized 132 kV transmission line to 230 kV
bundled 795 MCM construction between Bennett Mountain and Mora Substations. This
alternative utilizes the 406 line route (originally was the Upper Salmon to Caldwell line) which
passes in the vicinity of both Bennett Mountain and Evander Andrews. The west end of this
new 230 kV line is assumed to terminate at a new 230 kV Mora Substation, which is folded
into the Boise Bench-Caldwell 230 kV line. No 230/138 kV transformer is modeled to tie the
two Mora busses. A 230/138 kV 200 MV A transformer(duplicate of the Midpoint unit) was
modeled at Evander Andrews to improve system performance under N-l conditions. Studies
also revealed the need to reconductor/rebuild the Evander Andrews to Mountain Home
Junction 138 kV line, with this alternative.
Post-transient Study Results
This Interconnection Feasibility Study Report is for Network Resource Interconnection Service
at 230 kV, for a 91/99 MW simple cycle gas turbine at the Bennett Mountain Power Plant.
System transfers across the Midpoint West cutplane are modeled at 1100 MW prior to the
proposed transmission improvements or the proposed generator producing any power. Hydro
generation production for the Boise & Snake plants, were modeled at heavy, but realistic
levels. Ouput levels for the existing peakers at Evander Andrews and Bennett Mountain were
varied over their operating ranges as appropriate. N -0 and N -1 outage performance for the
existing system are recorded. As agreed in the Scoping Meeting, three alternatives were
evaluated. For each alternative, the new generator s output was taken to its summer
temperature maximum level of 91 MW and system conditions recorded for both N-O and N-
outages.
Existin2 System
The following one line diagram depicts the existing system with no outages.
MldDolnt West .. 1100 MW
Existing System - No Outages
Figure 1
For the existing system, seven N-l outages produce overloads that exceed the continuous
rating of elements of the transmission system. The N-l' s that produce overloads with the
existing system are included in Appendix B , Figures 9-15.
Alternative #1
The following one line diagram depicts the system with Alternative #1 added, full summer
output of the generator, and with no outages.
BOISEBCH1.0 p'
MIOLOC31 MIO'OINT01" 1.00p'
Alternative #1 - No Outages
Figure 2
Alternative #1 has multiple N-l outages that produce overloads that exceed 115% of
continuous ratings. Some of the resulting overloads are reduced with the addition of the
Evander Andrews 230/138 kV transformer, and others are increased.
The Rattlesnake to Boise Bench #2230 kV line outage produces some of the larger overloads.
The following one line depicts a 128 % loading on the Mountain Home Junction to Lucky Peak
138 kV line, without the Rattlesnake 230/138 kV transformer.
Mid oint West = 927 MW
Alternative #1 - Rattlesnake-Boise Bench #2 230 k V Outage
Without the Rattlesnake 230/138 kV Transformer
Figure 3
Adding the Rattlesnake 230/138 kV Transformer to the above outage, produces a 171
loading on the Mountain Home Junction to Lucky Peak 138 kV line.
With the Rattlesnake 230/138 kV transformer in-service, no other N-l outage produces
overloads that exceed 115% loading.
Without the Rattlesnake 230/138 kV transformer in-service, four other N-l outages produces
overloads that exceed 115% loading and are also greater than existing system overloads for the
same N-l. They are:
Rattlesnake3 - Boise Bench #3 230 kV Line outage
Midpoint - Rattlesnake #2 230 kV line outage
Evander Andrews - Strike 138 kV line outage
Strike - Bowmont 138 kV line outage
Several other N -1 outages result in overloads below 115 % that would require curtailments
following the outage to get down to loadings that can be sustained continuously
Alternative #1 is an unacceptable alternative, due to the N-l outage that produces overloads
that exceed 115% of continuous ratings. The Network Rating for Alternative #1 is 0 MW.
Alternative #2
The following one line diagram depicts the system with Alternative #2 added, full summer
output of the generator, and with no outages.
Mid oint West = 1102 MW
Alternative #2 - No Outages
Figure 4
The addition of the Evander Andrews 230/138 kV transformer improves the performance of
Alternative #2 for all N-l outages. Alternative #2 has no N-l outages that produce overloads
that exceed 115% of continuous rating.
Curtailments are required for all three N-l outages of the 230 kV lines from the Mountain
Home area into Boise Bench. The following one line diagram depicts the system with
Alternative #2 added, full summer output of the generator, and the outage of the Boise Bench -
Rattlesnake #1 230 kV line.
Mid oint West = 1051
Alternative #2 - Rattlesnake-Boise Bench #1230 kV Outage
With the Proposed Unit (g) 91 MW Output
Figure 5
Loss of the Rattlesnake to Boise Bench #1 line require the proposed unit's output to be lowered
to approximately 70 MW to reduce the Boise Bench to Rattlesnake #2 overload to 100% of the
continuous rating or a level that the overload is no worse than it is for the existing system with
the same N-l outage. These contingencies and resulting system performance determines the
Network Resource Rating to be 70 MW for Alternative #2. The following one line diagram
depicts the same outage as Figure 5 above, but the output of the proposed unit has been
curtailed to 70 MW to relieve the overload on the Boise Bench to Rattlesnake #2230 kV line.
Mid oint West = 1055
Alternative #2 - Rattlesnake-Boise Bench #1230 kV Outage
With the Proposed Unit (g) 70 MW Output
Figure 6
The loss of the Midpoint to Boise Bench #3 230 kV line requires a curtailment to lower a
120% overload of the series capacitors on the Midpoint to Rattlesnake #2 230 k V line. This
alternative does not permit the overload to be reduced by lowering the output of the proposed
unit. Lowering the output of the proposed unit will increase the overload on the series
capacitors in question. Other generators would have to be curtailed to solve this overload
scenarIo.
Alternative #2 will require curtailments of the proposed generators output following multiple
loutages. As a result, Alternative #2 does not provide acceptable performance for Network
Resource Interconnection Service for the proposed unit at full output. The Network Resource
Rating for Alternative #2 is 70 MW. Alternative #2 is also believed to very similar in cost to
Alternative #3, yet it's performance is much more problematic than Alternative #3.
10-
Alternative #3
The following one line diagram depicts the system with Alternative #3 added, full summer
output of the generator, and with no outages.
MldDolnt West.. 1118 MW
Alternative #3 - No Outages
Figure 7
The addition of the Evander Andrews 230/138 kV transformer improves the performance of
Alternative #3 , for all of the N-l outages. With the Evander Andrews 230/138 kV transformer
in service, alternative #3 has no N-l outages that produce overloads that exceed 115% of
continuous ratings.
One N -1 outage results in an overload below 115 % and at a level that the overload is greater
than it is for the existing system with the same N-l outage. The loss of the Midpoint to Boise
Bench #3 230 kV line results in a 116% loading on the series capacitor of the Midpoint to
Rattlesnake #2230 kV line. This series capacitor is capable of 110% loading continuously, so
a 6% reduction in flow is required. Lowering generation in the Mountain Home area results in
increased flow on the series capacitor bank, so transfers across the Midpoint West cutplane
will need to be reduced to correct this overload, as well as prepare for the next contingency.
Alternative #3 changes the characteristics of the interconnected network enough to create the
need to reconductor/rebuild the Evander Andrews to Mountain Home Junction 138 kV line.
For the N-l outage of the Lucky Peak to Micron 138 kV line, the Evander Andrews to
Mountain Home Junction 138 kV line loads to 114% of its rating with all the peaking
generation in the Mountain Home area at full output. If the output of the peaking generation in
the Mountain Home area is reduced, the overload increases in magnitude. The following one
line diagram depicts the Lucky Peak to Micron 13 8 k V line outage with all the Mountain
Home area peaking generation off-line.
11-
Alternative #3 - Luck Peak to Micron 138 kV Line Outage
With Peakers Off-line
Figure 8
Alternative #3 is the recommended alternative for the proposed unit at 91/99 MW for Network
Resource Interconnection Service.
Cost Allocation of Proposed Improvements
Alternative #3 contains the following five construction components:
Bennett Mountain to Evander Andrews 230 kV line and terminals
Evander Andrews to Mora 230 kV line and terminals
230 kV generator connection terminal at Bennett Mountain
Evander Andrews 230/138 kV transformer and terminals
Reconductor/rebuild of the Evander Andrews to Mountain Home Junction 138
kV line
A cursory attempt has been made in this study to characterize each transmission improvement
as either "needed to integrate the proposed generator" or "needed to correct existing
operational concerns . The costs associated with those improvements believed to be "needed
to integrate the proposed generator" are allocated to the generator interconnection. The costs
associated with those improvements believed to be "needed to correct existing operational
concerns " are allocated to IPCo Delivery.
12-
Approximate estimated costs allocated to the generator interconnection are:
$16.5 Million - Bennett Mountain to Mora 230 kV line construction costs
$ 2.6 Million - Mora 230 kV substation
1.4 Million - Bennett Mountain substation improvements
$20.5 Million - Total estimated generator interconnection cost
Approximate estimated costs allocated to the IPCo Delivery are:
$ 3.5 Million - Evander Andrews 230 kV & 138 kV substation improvements
$ 1.7 Million - Evander Andrews to Mountain Home Junction 138 kV line rebuild
$ 5.2 Million - Total estimated allocation to IPCo Delivery
These cost estimates include direct equipment and installation labor costs, indirect labor costs
and overheads , and allowance for funds used during construction (AFUDC). The proposed
cost allocation is subject to change, as more information is known. These are cost estimates
only and final charges to the customer will be based on the actual construction costs incurred.
10.Short Circuit Study Results
Preliminary short circuit study results indicate the surrounding circuit breakers are believed to
be able to accommodate the increased fault duty. No circuit breaker replacements are
anticipated at this time.
11.Conclusions
The feasibility of interconnecting a 91/99 MW simple cycle gas turbine at Bennett Mountain Power
Complex to Idaho Power s 230 kV transmission system was studied. Three interconnection
alternatives were evaluated. Alternative #1 was found to be an unacceptable alternative due to
transmission system loadings that exceeded 115% for a N-l outage. Alternative #2 did not provide
acceptable performance for Network Resource Interconnection Service for the proposed unit at full
output. The Network Resource Rating for Alternative #2 is 70 MW. Alternative #3 was found to
be an acceptable interconnection alternative. While Alternative #3 does require minimal
redispatch/transmission switching for one N-l outage, it is minor in nature and deemed acceptable
for this feasibility study. The estimated total cost of the transmission improvements associated with
Alternative #3 is approximately $26 Million. At this time it is believed that approximately $21
Million of these estimated costs should be allocated to the generator interconnection.
13-
APPENDIX A
Method of Study
The study methodology inserts the proposed generator up to the maximum requested summer
output of 91 MW into the selected WECC power flow case and then, using the PowerWorld
Simulator powerflow program, examines the impacts of the new resource on Idaho Power
transmission system (lines , transformers, etc.) within the study area under various
operating/outage scenarios. The WECC and Idaho Power reliability criteria and Idaho Power
operating procedures were used to determine the acceptability of the alternatives considered.
The WECC case is a recent cases modified to simulate stressed but reasonable pre-contingency
energy transfers utilizing the IPC system.
Acceptability Criteria
The following acceptability criteria were used in the power flow analysis to determine the
acceptability of the alternatives:
Loadings on transmission lines and transformers should not exceed 115% of the
continuous rating, immediately flowing any N-l outage. Loading on the Midpoint 230
kV series capacitors should not exceed 135% of the continuous rating, immediately
flowing any N-l outage. These loadings levels of 115% on transmission lines and
transformers and 135% on Midpoint series capacitors correspond to IPCo s 30 minute
emergency equipment ratings. Any loadings immediately following an N-l outage
less than the 30 minute emergency rating is acceptable.
Loadings which are less than the 30 minute emergency equipment ratings, but greater
than the equipment continuous ratings , must be reduced to the continuous ratings by
generation curtailments, re-dispatch, or some other operating procedure. Any remedial
action schemes(RAS) or other transmission switching, must be judged to be reasonable
before the alternatives performance can be deemed acceptable.
The continuous rating of equipment is assumed to be the normal thermal rating of the
equipment. This rating will be as determined by the manufacturer of the equipment or
as determined by Idaho Power. Less than or equal to 100% of continuous rating for
transmission lines and transformers is acceptable. Less than or equal to 110% of
continuous rating for the Midpoint 230 kV series capacitors is acceptable.
Transmission voltages, under normal operating conditions, are maintained within plus
or minus 5% (0.05 per unit) of nominal. Therefore, voltages greater than or equal to
95 pu voltage and less than or equal to 1.05 pu voltage are acceptable.
The stable operation of the transmission system requires an adequate supply of volt-
amperes reactive (V ARs) to maintain a stable voltage profile under both steady-state
and dynamic system conditions. An inadequate supply of V ARs will result in voltage
14-
decay or even collapse under the worst conditions. Idaho Power designs its system to
integrate Network Resources at full capability during specified outage conditions.
Equipment/line/path ratings used will be those that are in use at the time of the study or that are
represented by IPC upgrade projects that are either currently under construction or whose
budgets have been approved for construction in the near future. All other potential future
ratings are outside the scope of this study. Future transmission changes may, however, affect
current facility ratings used in the study.
15-
APPENDIX B
l Outages That Produce Overloads On The Existing System
The following one line diagrams depict system performance following the seven N-l outages
that produce overloads which exceed the continuous rating of facilities. Figure 1 on page 5
depicts the operation of the existing system with no outages. The combination of heavy hydro
and peaker generation in the Mountain Home area, and 1100 MW east to west transfers on
Midpoint West, results in the Mountain Home Junction to Lucky Peak and Lucky Peak to
Micron 138 kV lines being loaded to 98% & 99% respectively, prior to any outages.
Mld olnt West.. 981
Existing System - Midpoint to Boise Bench #3230 kV Outage
Figure 9
16-
MldDolnt West.. 951
Existing System - Rattlesnake to Boise Bench #2 230 kV Outage
Figure 10
Mld olnt West. 997
Existing System - Midpoint to Rattlesnake #2 230 k V Outage
Figure 11
17-
MldDolnt West.. 1053
Existing System - Midpoint to DRAM #1230 kV Outage
Figure 12
Mld olnt West.. 1085
Existing System - CJ Strike to Bowmont 138 k V Outage
Figure 13
18-
""""'"'-"
MldDolnt West.. 1072
Existing System - Lucky Peak to Micron 138 kV Outage
Figure 14
MldDolnt West.. 1094
Existing System - Evander Andrews to CJ Strike 138 kV Outage
Figure 15
19-
LARGE GENERATOR INTERCONNECTION
FEASIBILITY STUDY REPORT
for the
230 KV INTERCONNECTION OPTION
MIDDLETON SITE
for
Idaho Power Company - Power Supply, Interconnection Customer
for connection of
A 200 MW OR 94 MW SIMPLE CYCLE GAS TURBINE PEAKING PROJECT
MIDDLETON SITE
IDAHO POWER COMPANY, Transmission Provider
TRANSMISSION SYSTEM
FINAL REPORT
September 12, 2005
'" "
Introduction
Idaho Power Company - Power Supply has contracted with Idaho Power Company (IPC) to
perform a Large Generator Interconnection Feasibility Study for Network Resource
Interconnection Service at 230 kV for the integration of either a new 200 MW or 94 MW
simple cycle gas turbine peaking project. The proposed location is the Middleton Site located
within the Middleton Industrial Park approximately 1.5 miles Southeast of Middleton, Idaho.
This report documents the basis for and the results of this Feasibility Study. It describes the
proposed interconnection alternatives, the study cases used, outage scenarios assumed and
results of all work in the areas of concern.
Summary
The performance of a 230 kV interconnection alternative was evaluated to integrate a 200 MW
simple cycle gas turbine, located at the Middleton Site, into the Idaho Power System. A
detailed description ofthe location of the Middleton Site can be found in Section 5.0 of this
report. Idaho Power Company - Power Supply has requested Interconnection Feasibility
Studies for two units of different sizes at the Middleton Site. The larger unit is rated 200 MW
(fY -7 degrees C(winter rating) and 174 MW (fY 32 degrees C(summer rating). The smaller unit
is rated 94 MW (fY -7 degrees C(winter rating) and 86 MW (fY 32 degrees C(summer rating). It
is our understanding that only one unit will be selected for construction at this time. The same
230 kV interconnection alternative was selected for evaluation for each proposed unit.
The 230 kV interconnection alternative performed acceptably for the 174/200 MW unit. This
interconnection alternative is estimated to cost approximately $2.7 million. The smaller 86/94
MW unit will require the same interconnection facilities, thus have the same interconnection
cost. We find no reason to believe the smaller unit would result in operational problems that
were not apparent for the larger unit.
These cost estimates include direct equipment and installation labor costs, indirect labor costs
and overheads, and allowance for funds used during construction (AFUDC). These are cost
estimates only and final charges to the customer will be based on the actual construction costs
incurred.
Summary of Interconnection Request
A request was made to Idaho Power Co. by Idaho Power Company - Power Supply to study the
interconnection of either a proposed 174/200 MW or a proposed 86/94 MW simple cycle gas
turbine at the Middleton Site, near Middleton, Idaho, to Idaho Power s transmission system at
the 230 kV level for Network Resource Interconnection Service.
Scope of Interconnection Feasibility Study
The Interconnection Feasibility Study was done and prepared in accordance with the FERC
Order 2003-, Standard Large Generator Interconnection Procedures, to provide a preliminary
evaluation of the feasibility of the interconnection of the proposed large generating project to
the Idaho Power transmission system. This study will only be concerned with the capabilities
of the Idaho Power system to manage this new resource within the study area of the proposed
interconnection.
Description of Proposed Generating Project
Idaho Power Company - Power Supply proposes to connect one or the other of two different
sized simple cycle gas turbines to the Idaho Power 230 kV transmission system, at the
Middleton Site. The Middleton Site is located at Boise Meridian Township 4N, Range 2W
SE1I4 ofNW1I4 of Section 17. The larger unit is rated 200 MW (fY 7 degrees C(winter
rating) and 174 MW (fY 32 degrees C( summer rating). The smaller unit is rated 94 MW (fY
degrees C(winter rating) and 86 MW (fY 32 degrees C(summer rating). It is our understanding
that only one unit will be selected for construction at this time.
The equipment for the larger unit is described as being, a Siemens SGT6-5000F CT ECNO
Pack. The general equipment description for the smaller unit is a GE LM 6000 Package (2
units) or GE 7F A Package (1 unit). The proposed commercial operation date is April 1 , 2007
for either unit.
Description of Existing Transmission Facilities
The Middleton Site geographically lies adjacent to the Caldwell to Locust 230 kV transmission
line. The closest 138 kV line is approximately 3.5 miles away. At the Scoping Meeting for
these Interconnection Requests, it was agreed that the interconnection voltage to be stu(ij,
would be 230 kV. It was anticipated that the cost of a 138 kV alternative would be greater than
the 230 kV alternative with no apparent performance advantage. .
The Mj,~dleton Site is approximately 4.6 circuit line miles out of the Caldwell Substation on
the Caldwell to Locust 230 kV line.
,,-
Description of Configurations Studied
Since the most limiting operating conditions are expected during summer peak load conditions
the injection of the simple cycle gas turbine s 174 MW summer rated output was inserted into
a 2006 power flow case that would simulate peak summer loads in the Boise area.
The interconnection alternative selected for evaluation was a fold of the Caldwell to Locust
230 kV line and construction of a new 230 kV substation utilizing three 230 kV circuit
breakers. The three terminal ring bus configuration would accommodate the generator
terminal, the Caldwell to Middleton Site 230 kV line terminal, and the Locust to Middleton
Site line terminal.
Post-transient Study Results
This Interconnection Feasibility Study Report is for Network Resource Interconnection Service
at 230 kV, for a 174/200 MW or 86/94 MW simple cycle gas turbine at the Middleton Site.
The studies evaluate system performance for all levels of production from 0 MW output, up to
its maximum rating for the summer season. For this study, there is no reason to believe the
smaller unit would create operational problems, if the larger unit did not. N-O and N-l outage
performance for the existing system are recorded. For this alternative, the new generator
' '
output was taken to its maximum summer rating of 174 MW and system conditions recorded
for both N-O and N-l outages.
Existing System
The following one line diagram depicts the existing system with no outages.
~~\!'M
Existing System - No Outages
Figure 1
174 MW Middleton Generator Added
The following one line diagram depicts the system with the Middleton Generator at full output
and with no outages.
BROWNLEE1.043 u
174 MW ~ Middleton Site - No Outages
Figure 2
Single Contingency Line Outage Performance
Four single contingency line outages (N-l) will be considered to evaluate system performance
following the generator addition. The following one line depicts system performance following
the loss of the Boise Bench to Locust 230 kV line, with the generator at 174 MW output.
174 MW (ID Middleton Site - Boise Bench to Locust 230 kV Line Outage.
Figure 3
For col1lparison purposes, the following one-line depicts the existing system perfonnance for
the same Boise Bench to Locust 230 kV line outage.
n~~~
Existing System - Boise Bench to Locust 230 kV Line Outage
Figure 4
The following one line depicts system performance following the loss of the Brownlee to
Ontario 230 kV line, with the generator at 174 MW output.
B'j\~WE
174 MW ~ Middleton Site - Brownlee to Ontario 230 kV Line Outage
Figure 5
For comparison purposes, the following one-line depicts the existing system performance for
the same Brownlee to Ontario 230 kV line outage.
BROWNLEE .1.044 u
Existing System - Brownlee to Ontario 230 kV Line Outage
Figure 6
The Brownlee to Ontario 230 kV line outage is critical in determining the timing ofthe next
major transmission system improvement project required for Treasure Valley load growth. For
the existing system with no generation at the Middleton Site, approximately 205 MW of
Nampa/Caldwell area load growth can be accommodated before major transmission
improvements are required. With 174 MW of generation at the Middleton Site, about 315 MW
ofload growth in the Nampa/Caldwell area can be accommodated before major transmission
system improvements are required. As a result, the utilization ofthe Middleton Site will
:,.
significantly delay the schedule for the next major transmission system improvement to
accommodate load growth in the Nampa/Caldwell area.
The following one line depicts system performance following the loss of the Locust to
Middleton Site 230 kV line, with the generator at 174 MW output.
,~ma;
174 MW ~ Middleton Site - Locust to Middleton Site 230 kV Line C)utage
Figure
The following one line depicts system performance following the loss ofthe Caldwell to
Middl~ton Site 230 kV line, with the generator at 174 MW output.
c':
BROWNLEE1.043
174 MW ~ Middleton Site - Caldwell to Middleton Site 230 kV Line Outage
Figure 8
For comparison purposes, the following one-line depicts the existing system performance for
the same Caldwell to Locust 230 kV line outage.
Existing System - Caldwell to Locust 230 kV Line Outage
Figure 9
The 230 kV interconnection alternative exhibits acceptable performance for all conditions
studied. No single contingencies examined produced overloads or unacceptable voltage levels.
Utilizing the Middleton Site will delay the schedule for the next major transmission system
improvement to accommodate load growth in the Nampa/Caldwell area.
Estimated Cost of Proposed Improvements
Cost estimates for the 230 kV interconnection alternative were generated for two categories of
costs:
Transmission Line Costs
Substation Costs
Approximate estimated costs for the Middleton Site interconnection alternative are:
$ 2 687
$ 2 687 500
- Transmission Line Costs
- Substation Costs
- Total estimated generator interconnection cost
These cost estimates include direct equipment and installation labor costs, indirect labor costs
and overheads, and allowance for funds used during construction (AFUDCr No tax gross-up
is included in these estimates. These are cost estimates only and final charges to the customer
will be based on the actual construction costs incurred.
10.Short Circuit Study Results
Preliminary short circuit study results indicate five 138 kV circuit breakers at Boise Bench will
need to be replaced to be able to accommodate the increased fault duty. More detailed short
circuit analysis will be required to determine with certainty whether replacement of all five
breakers will be required. Additional short circuit studies will be required if either of these
generator interconnection projects proceed to a system impact study. If the additional short
circuit analysis studies still require breaker replacements, cost estimates will be developed at
that time.
11.Conclusions
The feasibility of interconnecting either a 174/200 MW or 86/94 MW simple cycle gas turbine at
the Middleton Site to Idaho Power s 230 kV transmission system was studied. The 230 kV
interconnection alternative evaluated was found to provide acceptable system performance for
either of the proposed generators. Utilizing the Middleton Site will delay the schedule for the next
major transmission system improvement to accommodate load growth in the Nampa/Caldwell area.
The estimated total cost ofthe transmission improvements associated with the 230 kV
interconnection alternative is approximately $2.7 Million.
...,..
'n.
:.~";
APPENDIX A
Method of Study
The study methodology inserts the proposed generator up to the maximum requested output of
174 MW into the selected WECC power flow case and then, using the PowerWorld Simulator
powerflow program, examines the impacts ofthe new resource on Idaho Power s transmission
system (lines, transformers, etc.) within the study area under various operating/outage
scenarios. The WECC and Idaho Power reliability criteria and Idaho Power operating
procedures were used to determine the acceptability of the alternatives considered. The WECC
case is a recent cases modified to simulate stressed but reasonable pre-contingency energy
transfers utilizing the IPC system.
Acceptability Criteria
The following acceptability criteria were used in the power flow analysis to determine the
acceptability of the alternatives:
Loadings on transmission lines and transformers should not exceed 115% of the
continuous rating, immediately flowing any N-l outage. Loading on the Midpoint 230
kV series capacitors should not exceed 135% of the continuous rating, immediately
flowing any N-l outage. These loadings levels of 115% on transmission lines and
transformers and .135% on Midpoint series capacitors correspond to IPCo s 30 minute
emergency equipment ratings. Any loadings immediately following an N-l outage
less than the 30 minute emergency rating is acceptable.
Loadings which are less than the 30 minute emergency equipment ratings, but greater
than the equipment continuous ratings, must be reduced to the continuous ratings by
generation curtailments, re-dispatch, or some other operating procedure. Any remedial
action schemes(RAS) or other transmission switching, must be judged to be reasonable
before the alternatives performance can be deemed acceptable.
The continuous rating of equipment is assumed to be the normal thermal rating of the
equipment. This rating will be as determined by the manufacturer of the equipment or
as determined by Idaho Power. Less than or equal to 100% of continuous rating for
transmission lines and transformers is acceptable. Less than or equal to 110% of
continuous rating for the Midpoint 230 kV series capacitors is acceptable.
Transmission voltages, under normal operating conditions, are maintained within plus
or minus 5% (0.05 per unit) of nominal. Therefore, voltages greater than or equal to
95 pu voltage and less than or equal to 1.05 pu voltage are acceptable.
The stable operation of the transmission system requires an adequate supply ofvolt~
amperes reactive (V ARs) to maintain a stable voltage profile under both steady-state
and dynamic system conditions. An inadequate supply of V ARs will result in voltage
decay or even collapse under the worst conditions. Idaho Power designs its system to
integrate Network Resources at full capability during specified outage conditions.
. .
Equipment/line/path ratings used will be those that are in use at the time of the study or that are
represented by IPC upgrade projects that are either currently under construction or whose
budgets have been approved for construction in the near future. All other potential future
ratings are outside the scope of this study. Future transmission changes may, however, affect
current facility ratings used in the study.
10-