Economic Planning Study MWWG Economic Study Results

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Economic Planning Study MWWG Economic Study
Results

• Presentation to TRANSAC on 10/23/08

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Objectives

• Evaluate Transmission Impacts caused by
  installation of wind farms in selected high wind
  areas
• Quantify congestion for various levels and
  locations of new generation
• Transmission upgrades necessary to accommodate
  500 MW of new generation under N-0 conditions.

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Study Assumptions Scenarios

• GE 1.5 MW machines used to model the wind farm.
• An equivalent Machine of 100 MW, 250 MW and 500
  MW were put at the defined location.
• 2008 Light Autumn case used as it was the most
  recent available case for the existing system
  without new GIAs.
• MT-NW was increased by the equivalent amount in
  order to keep the same dispatch pattern
• Judith Gap kept at 135 MW
• No MATL

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Study Assumptions Scenarios

• New Generation in three different high wind areas
  were studied
• Glacier/ Toole County
• Generation Connected at South Cut Bank 115 KV and
  Shelby auto 115 kV
• Wheatland/ Judith Basin
• The total generation was connected to Judith Gap
  230 kV bus.
• Park/ Sweet Grass/ Stillwater
• The total generation was connected to Col. Raplje
  161 kV bus

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Path 8 Load Duration Curve for 2007
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Path 18 Load Duration Curve for 2007
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Preliminary Results Glacier / Toole County
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Preliminary Results Glacier Toole County
North of Great Falls (NOGF)

• Thermal overloads seen for N-0 conditions for
  high level generation in the NOGF area.
• The 230/ 115 kV auto bank at Shelby for 250 MW
  and higher
• 115 kV lines overload in Cut Bank and Conrad for
  500 MW generation.
• Overload in the Havre-Rudyard area for 500 MW
  generation.
• Thermal overloads seen on the 115 kV system due
  to N-1 credible N-2 contingencies. ( Causes
  overloads in the WAPA control area on the Havre-
  Rudyard area)
• Limited due to thermal rating of the 115 kV GEC
  line between South Cutbank and Shelby.
• Low Voltages seen on 69 kV under N-1 and N-2
  conditions in Bole area

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Load Duration Curve for NOGF
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Load Duration Curve for NOGF with 100 MW, 250 MW
and 500 MW request with Limiting Constraints
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Preliminary Results South of Great Falls

• There are some segments approaching its thermal
  capability under certain N-1 outages in the SOGF
  path
• E.g. East Helena to Canyon Ferry lines on the
  outage of the Great Falls to Ovando 230 kV line.
• Credible N-2 of Great Falls to East Helena 100 kV
  line overloads the Great Falls to Holter line.
• Limiting constraints dependent on the Load and
  hydro generation in Great Falls.
• The limiting constraints presented in the curves
  are preliminary. The values of the limiting
  constraints may change as more detailed studies
  are performed.

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Preliminary Transient Stability Analysis

• Preliminary analysis have shown an increase in
  the trip amount of Colstrip for the 500 kV
  contingencies.
• No other major dynamic issues were seen.
• Special Protection Schemes may be required in
  order to maintain the stability of the system
  during certain outages.

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Mitigations Required for 500 MW under N-0
Conditions

• Upgrade of the 230/115 kV bank at Shelby
• Upgrade of the CTs on WAPAs 230 kV line.
• A new 230 kV line from South Cut Bank to Great
  Falls
• A new 230 kV Substation at South Cut Bank with a
  new 230 /115 kV transformer bank at South Cut
  Bank.
• Upgrade of the 500 kV transmission system in
  order to accommodate higher flows
• 70 series Compensation on the 500 kV system.
• Increased Ampacity on the 500 kV in order to
  accommodate higher flows.

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Preliminary Results Wheatland Judith Basin
County

• Outage of the 230 kV line from Judith Gap to
  Broadview causes overload on the underlying 100
  kV system.
• Outage of the 230 kV line from Judith Gap to
  Great Falls also causes an overload on the 230
  /100 kV auto bank at Judith Gap.
• 230 /100 kV auto bank overload under certain N-1
  and N-2 conditions for 100, 250 and 500 MW
  generation.
• Preliminary Study shows this to be the limiting
  constraints for the South of Judith Gap (SOJG).
  Further analysis required in order to determine
  the correct limit for SOJG.
• Increases loading on the series capacitor banks
  at Broadview in the event of outage of the
  parallel 500 kV line for 250 MW and higher
• Overload on the 100 kV due to Credible N-2
  contingencies.

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South of Judith Gap (SOJG) Load Duration Curve
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South of Judith Gap (SOJG) Load Duration Curve
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South of Judith Gap (SOJG) Load Duration Curve
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Transient Stability Analysis

• The 500 kV contingencies showed increased amount
  of Colstrip tripping under the conditions
  studied.
• The new generation was required to drop in order
  to maintain the stability of the system.

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Mitigations Required for 500 MW under N-0
Conditions

• Upgrade of the 230/100 kV Auto bank at JudithGap
  Tap.
• Upgrades to the 500 kV system in order to
  accomodote higher flows.
• 230/500 kV auto banks at Broadview
• Series Compensation at Broadview, Garrison, Taft.
  
• Ampacity on the 500 kV lines
• SPS to drop the generation units under certain
  outages to maintain the stability of the system.

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Preliminary Results - Park/ Sweet Grass County

• N-0 Overloads for the 500 MW generation.
• 161 kV system in the Columbus Rapleje Area
  overload.
• N-1 Outage of the 161 kV line causes overload on
  the underlying system.
• Melville Big Timber 50 kV
• Limiting constraints for the Columbus Rapleje
  load duration curve is under study.

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Transient Stability Analysis

• Preliminary analysis shows increase in the
  tripping at Colstrip for the 500 kV contingencies
• SPS required to maintain the stability of the
  system under certain conditions.

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Mitigations Required for 500 MW

• Connection of the 230 to 161 kV at Columbus
  Rapleje.
• Upgrade to the 500 kV transmission system in
  order to accommodate higher flows.
• 230/500 auto banks at Broadview
• Series Compensation

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Future Work

• Report