Customer Meeting April 28, 2010 Torrington, WY

Agenda Introductions Accomplishments Update on Torrington Area PVVC Overview PVVC Schedule and Cost Estimates Questions/Comments Wrap Up

Accomplishments since 2003 Whiterock Substation (2005) Lingle Tap (2003) Lyman-Yoder Tap (2005) McGrew area Caps (2005) Stored mobile transformer at Guernsey Rural (2004) Wood Pole Testing and Treatment (2003 & 2004) Letter of Concurrence between Tri-State and Western on Platte Valley conversion project (2005) Glendo Substation Relay System & RTU replacement

Accomplishment since 2003 Gering Station Service Switchgear (2006) Gering PCBs 162, 462, 966 replacement (2006) Glendo PCB 524 (2006) Limestone additions (PCB 442, new control & relay system, new RTU) (2009) Repaired Mobile transformer and returned to Guernsey Rural (2009)

Upcoming Projects ( ) Torrington transformer KY2A addition (In-service May 2010) Gering-Gering Valley 34.5-kV rebuild (2011)

Torrington KY2A addition Project to add 115/34.5-kV 50 MVA transformer Joint project with City of Torrington Transformer delivered - Oct 2008 Construction contractor complete – Dec 2008 Control Design & switchboard delivered Commissioning ongoing

Platte Valley Voltage Conversion The objective of the Platte Valley Voltage Conversion Project is to convert the operating voltage of the kV transmission lines and related facilities between Lingle Substation and Sievers Rural Substation to 69- kV. The lines were rebuilt in the early 90’s to 69-kV standard.

Platte Valley Voltage Conversion The majority of the work is converting the numerous substations and taps along the line segments to 69-kV. Western and Tri-State signed a Letter of Concurrence in November 2004 laying the initial scope and responsibilities for the upgrades.

Platte Valley Voltage Conversion Scope: Lingle Substation: Install a 115/69-kV 40 MVA transformer and associated equipment. Torrington Substation: Install a 69/34.5-kV 50 MVA transformer and associated equipment. Sievers Rural Tap: Install a 69/34.5-kV 25 MVA transformer and associated equipment. Construct eleven miles of new 69-kV line between East Morrill Tap and Sievers Rural Tap.

Platte Valley Voltage Conversion Scope (cont): Torrington Rural Tap: Replace transformer and rebuild high side for 69-kV. Henry Tap: Replace transformer and rebuild high side for 69-kV. Village of Morrill Tap: Make necessary modifications to operate existing dual winding transformer at 69-kV. Connect the Town of Lingle Tap to the Limestone-Lingle 34.5-kV line.

Platte Valley Voltage Conversion Scope (cont): Estimated Cost: $21M Planned ISD: FY2015 Project Manager: Roy Gearhart Current Status: Not planned to start until FY2012. System Studies updated every two years. System Studies planned for 2010.

Platte Valley Voltage Conversion Major Milestones to date Various System Studies: Meeting with Platte Valley Customers: April 2003 Western and Tri-State signed Ltr of Concurrence: November 2004 Meeting with Platte Valley Customers: April 2005 Meeting with Platte Valley Customers: April 2007 Published Platte Valley Voltage Conversion Project Overview: January 23, 2006

Platte Valley Voltage Conversion Lingle Substation Scope: 115kV/69kV 40MVA transformer with high and low side interrupters for protection. New Substation site required for 115/69kV additions New Control Building Schedule: Estimate: $4,730k (In 2014 $’s)

Platte Valley Voltage Conversion Lingle Town Scope: Move connection to Limestone 34.5-kV line with ~0.5 mile of new 34.5-kV line. Schedule: Estimate: $100k - $200k (no detail estimate done)

Platte Valley Voltage Conversion Torrington Rural Scope: Convert to 69-kV with a 69kV/12.47kV 5MVA and a 69kV/24.9kV 7.5MVA transformers and 69kV improvements on high side. Schedule: Estimate: $1,500k (In 2014 $’s)

Platte Valley Voltage Conversion Torrington Substation Scope: New 69-kV yard with 4–69kV bays; 69kV/34.5kV 50MVA Transformer; New Control Building; more land. Schedule: Estimate: $5,400k (In 2014 $’s)

Platte Valley Voltage Conversion Henry Scope: Convert to 69-kV with a 69kV/12.47kV 7.5MVA transformer and 69kV improvements on high side. Schedule: Estimate: $900k (In 2014 $’s)

Platte Valley Voltage Conversion Village of Morrill Scope: Convert to 69-kV high side winding on existing 34.5/69/7.2/12.47kV 2.5MVA transformer and 69kV improvements on high side. Schedule: Estimate: No estimate done

Platte Valley Voltage Conversion East Morrill Tap – Wildcat 69-kV line Scope: Construct ~3 miles of new 69-kV line from East Morrill tap to Wildcat. Creates the Lyman-Wildcat 34.5-kV line. Allows Village of Lyman and Lyman Rural loads to remain 34.5-kV Schedule: Estimate: $1,395k (in 2012 $’s)

Platte Valley Voltage Conversion Wildcat Substation Scope: No new additions initially planned at Wildcat. Should the system needs change, the new Torrington-Sievers Rural 69- kV line could be interconnected with the 34.5-kV system at Wildcat to provide system reliability improvements.

Platte Valley Voltage Conversion Wildcat-Sievers Rural 69-kV line Scope: Construct a new 10 mile 69-kV line between Wildcat and Sievers Rural to bypass Mitchell area. Bypasses City of Mitchell and Mitchell Rural loads, leaving them at 34.5-kV Schedule: Estimate: $4,045K

Platte Valley Voltage Conversion Sievers Rural Scope: 69/34.5kV 20 MVA transformer with high and low side protection; new control building; land. Sievers Rural load remains served at 34.5-kV. Schedule: Estimate: $2,250k (In 2014 $’s)

Wrap Up Questions or Comments?

Thank You Contacts Bob Easton (Western) or Roy Gearhart (Western) or Stan Lawrenson (Tri-State) or