Transcript 06-Mitigation Update and Uncertainty Scenarios 2012-2013 Updated:2013-07-25 12:54 CS

Local Area Study
Mitigation Plan Update
and
Uncertainty Scenarios
2012 - 2013
Mitigation Plans Updates
 East Helena bus fault or transformer outage
» Ranked # 7 - Outages result in complete loss of the Helena 69 kV
system
» Construct 100 kV loop to radial fed Helena area 100 kV
distribution substation
» Tie proposed distribution substation needed for continued
growth in the Helena area to new 100 kV facilities
» Construct and tie new 100 MVA 100/69 kV auto substation to
new 100 kV facilities
» Add breakers to East Helena 69 kV bus to complete breaker-anda-half scheme
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Mitigation Plans Updates
 Broadview to Billings Area 230 kV double contingency
» Ranked # 8 - Outage results in low to very low voltage in the
Billings Area
♦ Problem worsens after loss of Corette and continued Billings area growth
» Build a new 230 kV line from Broadview into Billings
♦ Assumes slightly diverse route from existing Broadview to Billings 230 kV
lines
 Clyde Park bus fault or transformer outage
» Ranked # 13 - Outages result in loss of Livingston and Big
Timber Loads
» Upgrade Big Timber Auto to a 50 MVA transformer
» Reconductor weak 50 kV line near Big Timber
» Add capacitors to Big Timber and Livingston area distribution
substations
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Uncertainty Scenarios
Scenarios Considered:
 Extreme Winter
 Low Thermal, Heavy Import
 High Wind System Wide
 High Generation North of Great Falls (NOGF)
» Similar to stakeholder suggestion
Study Assumptions:
 N-0 and N-1 conditions considered
 All existing Special Protection Schemes considered
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Extreme Winter
Scenario Details
 2017 Extreme Winter load profile (1:50 forecast)
 Hydro plants significantly reduced
» Rivers/reservoirs partially frozen
 Thermal plants dispatched at max
» Corette assumed to be mothballed
 Wind dispatched at 5%
Scenario Findings
 230 kV and 161 kV systems more heavily relied on to supply the
underlying 100 kV systems
 Loss of Butte area 161/100 kV tie overloads remaining 161/100 kV tie
 100 kV system in Judith Gap area overloads from loss of major 230
kV line in Great Falls area
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Low Thermal, Heavy Import
Scenario Details
 2017 Heavy Summer load profile
 All major thermal plants are offline
 Wind dispatched at 5%
 Path 8 heavily importing
Scenario Findings
 Kalispell 115 kV tie line overloads (within emergency limits) for the
loss of Rattlesnake 230/161 kV auto transformer
 Loss of Butte area 161/100 kV tie overloads remaining 161/100 kV tie
 Steamplant bus outage causes additional overloads on Billings area
100 kV ties to the higher voltage BES
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High Wind System Wide
Scenario Details
 2017 Heavy Summer and Light Autumn load profiles
 Existing wind projects dispatched at capacity
 All other generation dispatched same as original case
 MATL has little to no flow at Great Falls
Scenario Findings
 No new thermal issues
 Minor high voltage under outage conditions identified in Two Dot
area
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High Generation NOGF
Scenario Details
 2017 Light Spring load profile
 Great Falls and NOGF area hydro generation at max
 Other Montana hydro dispatched same as original case
 Great Falls and NOGF area wind generation at max
 Remaining wind generation dispatched at moderate
levels
 MATL importing at Great Falls near 300 MW
 Path 8, 18, 80 transfers similar to original case
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High Generation NOGF
Scenario Findings
 Butte area 100 kV line heavily loaded under N-0
conditions
 Loss of Great Falls – Ovando 230 kV line overloads 100
kV lines in Helena area
 Loss of Great Falls – Judith Gap – Broadview 230 kV line
overloads 100 kV lines in Harlowton, Judith Gap, and
Broadview areas
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Conclusions
 System still robust in most areas, few new potential
problems found.
 Benefits of widely dispersed generation are
demonstrated.
 Potential weaknesses in the 100 kV system were
identified.
» Line or transformer upgrades and/or new facilities could be
required to mitigate problems observed.
 This analysis is “Informational” and not the primary
driver for mitigation.
» Because of the uncertain nature of these scenarios, formal
mitigation plans have not been developed.
» In some cases, new generation or TSR requests would drive
mitigation for problems observed.
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