Mitigation Plan Update and Uncertainty Scenarios 2012 2013 2 Mitigation Plans Updates East Helena bus fault or transformer outage Ranked 7 Outages result in complete loss of the Helena 69 kV system ID: 550336
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Slide1
Local Area Study
Mitigation Plan Update
and
Uncertainty Scenarios
2012 - 2013Slide2
2
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 substationTie proposed distribution substation needed for continued growth in the Helena area to new 100 kV facilitiesConstruct and tie new 100 MVA 100/69 kV auto substation to new 100 kV facilitiesAdd breakers to East Helena 69 kV bus to complete breaker-and-a-half schemeSlide3
3
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 growthBuild a new 230 kV line from Broadview into BillingsAssumes slightly diverse route from existing Broadview to Billings 230 kV linesClyde Park bus fault or transformer outageRanked # 13 - Outages result in loss of Livingston and Big Timber LoadsUpgrade Big Timber Auto to a 50 MVA transformerReconductor weak 50 kV line near Big TimberAdd capacitors to Big Timber and Livingston area distribution substationsSlide4
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Uncertainty Scenarios
Scenarios Considered
:
Extreme WinterLow Thermal, Heavy ImportHigh Wind System WideHigh Generation North of Great Falls (NOGF)Similar to stakeholder suggestionStudy Assumptions:N-0 and N-1 conditions consideredAll existing Special Protection Schemes consideredSlide5
5
Extreme Winter
Scenario Details
2017 Extreme Winter load profile (1:50 forecast)
Hydro plants significantly reducedRivers/reservoirs partially frozenThermal plants dispatched at maxCorette assumed to be mothballedWind dispatched at 5%Scenario Findings230 kV and 161 kV systems more heavily relied on to supply the underlying 100 kV systemsLoss of Butte area 161/100 kV tie overloads remaining 161/100 kV tie100 kV system in Judith Gap area overloads from loss of major 230 kV line in Great Falls areaSlide6
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Low Thermal, Heavy Import
Scenario Details
2017 Heavy Summer load profile
All major thermal plants are offlineWind dispatched at 5%Path 8 heavily importingScenario FindingsKalispell 115 kV tie line overloads (within emergency limits) for the loss of Rattlesnake 230/161 kV auto transformerLoss of Butte area 161/100 kV tie overloads remaining 161/100 kV tieSteamplant bus outage causes additional overloads on Billings area 100 kV ties to the higher voltage BESSlide7
7
High Wind System Wide
Scenario Details
2017 Heavy Summer and Light Autumn load profiles
Existing wind projects dispatched at capacityAll other generation dispatched same as original caseMATL has little to no flow at Great FallsScenario FindingsNo new thermal issuesMinor high voltage under outage conditions identified in Two Dot areaSlide8
8
High Generation NOGF
Scenario Details
2017 Light Spring load profile
Great Falls and NOGF area hydro generation at maxOther Montana hydro dispatched same as original caseGreat Falls and NOGF area wind generation at maxRemaining wind generation dispatched at moderate levelsMATL importing at Great Falls near 300 MWPath 8, 18, 80 transfers similar to original caseSlide9
9
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 areaLoss of Great Falls – Judith Gap – Broadview 230 kV line overloads 100 kV lines in Harlowton, Judith Gap, and Broadview areasSlide10
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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.