Integrated Transmission System Assessment

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Western South Dakota ... CEII Policy of any affected Transmission Owner (TO) identified in this document .... 2012: Continue with scheduled rebuild of Oahe Substation (final completion targeted for ... o Removal of UVLS in Pierre load pocket.
Integrated Transmission System Assessment Western South Dakota Area 4 (2012-2021) December 2011

Developed For: FERC Order 890 and NERC Standards TPL-001 through TPL-003

Prepared by: Western Area Power Administration Upper Great Plains Region Division of Transmission System Planning Billings, MT

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CRITICAL ENERGY INFRASTRUCTURE INFORMATION NOTICE

Materials contained in the complete study document include Critical Energy Infrastructure Information (CEII). All materials designated as CEII must be handled and protected in accordance with the CEII Policy of Western Area Power Administration (WAPA) and the CEII Policy of any affected Transmission Owner (TO) identified in this document or attached materials. In order to receive a complete study report, the requesting party will need to follow Western's Critical Energy Infrastructure Information (CEII) Policy. This CEII Policy is posted within Western's Effective Business Practices Folder (http://www.oatioasis.com/WAPA/WAPAdocs/Western-Common-Business-Practices.html). The direct link to the pdf file is http://www.oatioasis.com/woa/docs/WAPA/WAPAdocs/Western-OATT-BP-CEII-PolicyVersion-2010-0812.pdf. If the request for CEII can be granted, a Non-Disclosure and Confidentiality Agreement (NDA) will be offered you. A template of the NDA is also posted in Western's Effective Business Practices Folder. The direct link to the pdf file is http://www.oatioasis.com/woa/docs/WAPA/WAPAdocs/Western-OATT-Confidentiality-NDAAgreement-Form-Version-2010-0812.pdf.

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TABLE OF CONTENTS 0.0

EXECUTIVE SUMMARY ............................................................................................... 4

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INTRODUCTION.............................................................................................................. 6

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SCOPE OF STUDY ........................................................................................................... 7

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STUDY PROCEDURE ...................................................................................................... 7

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STUDY RESULTS ............................................................................................................. 8

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AREA SENSITIVITIES .................................................................................................. 19

5.1 Rapid City Area Load Pocket ......................................................................................... 19 5.2 Pierre Area Load Pocket ................................................................................................. 22 6.0

CONCLUSIONS AND RECOMMENDATIONS ......................................................... 24

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EXECUTIVE SUMMARY The purpose of this study is to evaluate and identify system additions needed in the Western, Basin, and Heartland Integrated System (IS). This is accomplished by analyzing near term and out-year summer and winter peak scenarios with best available load estimates and presently known transmission system planned facility additions. This effort will identify limiting transmission element(s) and potential problem areas where load serving capability is limited by voltage or thermal limitations. The goal is to maintain system reliability and customer load serving capability by identifying possible problems and resolving them before they appear. This study examines the high voltage (69 kV and above) transmission system in WAPA’s control area located within the Mid-continent Area Power Pool (MAPP) footprint. Rapid load growth has occurred in the Rapid City load pocket resulting in potential thermal and voltage violations for contingencies in the area. System improvements were planned as a part of the 890 study process, but UVLS is required until system improvements are in place. Rapid load growth has also occurred in the Pierre load pocket resulting in potential thermal and voltage violations for contingencies in the area. System improvements were planned as a part of the 890 study process, but UVLS is required until system improvements are in place. Unplanned Oil load growth is occurring in North Dakota. During system intact conditions this additional load does not have a major effect on the Western South Dakota system; however numerous Category B and C contingencies in North Dakota result in depressed voltage and increased thermal loading in the Western South Dakota region. Major system improvements are planned in the Western North Dakota/Eastern Montana area over the next 5 to 10 years. See the separate North Dakota reports for more information. Brief Summary of Results for Western South Dakota / Northern Nebraska (Area 4)  2011: Continue with scheduled replacement of Philip transformer (already in 890 Models, final completion targeted for June 2012)  2012: Continue with scheduled rebuild of Oahe Substation (final completion targeted for 2015) o Installation of additional UVLS may be required depending on load growth. o Installation of parallel 230/115 kV transformer o Populate existing 230 and 115 kV buses to double breaker/double bus o Eagle Butte – Oahe 115 kV line rating increase by replacing CTs such that this line rating is increased to at least 80 MVA. A rating of 104 MVA (limited by the bus/jumper ratings) is preferred. o Oahe – Philip Tap – New Underwood 230 kV line rating increase  Adjust/Replace CTs such that this line rating is increased to at least 320 MVA  A rating of 440 MVA (limited by the conductor rating) is preferred (would require LIDAR study)  2015: Construct Oahe – Ash Tap 115 kV line and abandon Ash Tap. o Requires rating increase of existing Ash Tap – Ash Street – Evans Street – Pierre line to conductor limit (112 MVA summer)

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 Requires CT setting changes and CT replacements  May require LIDAR study to increase to conductor limit o Removal of UVLS in Pierre load pocket 2012: Continue with scheduled upgrade of Fort Randall substation (final completion targeted for 2015) o Replace limiting jumpers and buswork o Install dedicated 230 and 115 kV breakers for two existing transformers o Installation of SPS for load shedding Pump Station 21 for loss of Fort Randall – Gregory 115 kV line 2012: Continue with scheduled system improvements in the Rapid City area (final completion targeted for 2015) o Sectionalizing New Underwood 230 and 115 kV buses o Installation of a parallel 230/115 kV transformer at New Underwood o Installation of a 230/115 kV transformer at RCDC tie o Installation of a 115 kV line from RCDC tie to RC o Removal of UVLS 2012: Study Nebraska Panhandle area for possible system improvements o Parallel 345/230 kV transformer at Stegall o Additional source to networked 115 kV system in Nebraska 2015: Install SPS/Generator Dropping scheme when Lower Brule – Witten 230 line is placed in service. o Will require additional study work to determine settings o PS 21 SPS will become for prior outage use only 2015: Construct Oahe – Ash Tap 115 kV line and abandon Ash Tap. o Requires rating increase of existing Ash Tap – Ash Street – Evans Street – Pierre line to conductor limit (112 MVA summer)  Requires CT setting changes and CT replacements  May require LIDAR study to increase to conductor limit o With the above facility improvements, study removal of UVLS in Pierre load pocket 2016: CT Increases on New Underwood – Rapid City lines: o New Underwood – Ellsworth and Ellsworth – Rapid City lines o New Underwood – Rushmore Tap – Rapid City line o Increase rating from 80 MVA to 120 MVA by changing CT settings and performing thermal studies on these lines 2016: Study Replacement of Newell 115/34.5 kV transformer

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