Naughton RAS (Southwest Wyoming Generation Tripping Scheme) – LAPS Presented by Seongtae Kim RASRS Meeting November 14-16, 2017

Current Transmission System and Existing Naughton RAS (SW WY Generation Tripping Scheme) – LAPS Current System The load in Park City area is served from Cottonwood radially. A second source will increase reliability of load service for this area. Existing RAS For outages of Naughton – Ben Lomond 230kV & Birch Creek – Ben Lomond 230kV lines RAS is armed when average flow of Naughton West & Evanston West paths is more than 900 MW. This N-2 outage causes overloading on Naughton – Treasureton 230kV line. For outages of Naughton – Ben Lomond 230kV & Naughton – Birch Creek 230kV lines RAS is armed when average flow of Naughton West & Evanston West paths is more than 1000 MW. This N-2 outage causes overloading on Painter – Long Hollow 138kV line.

New Transmission System New addition Croydon – Coalville – Silver Creek 138kV line (completion of Railroad – Croydon – Coalville – Silver Creek 138kV line) New Path Redefinition of Evanston West path due to the new line addition Modification of the existing RAS Due to addition of the new Croydon – Coalville – Silver Creek 138kV line, the existing RAS needs to be modified.

Outages of Naughton – Ben Lomond 230kV line & Birch Creek – Ben Lomond 230kV line (Credible N-2 Contingency)

Pre-contingency (Before outages of Naughton – Ben Lomond 230kV line & Birch Creek – Ben Lomond 230kV line) Normal (N-0) during light load & 820 MW flow on new Evanston West – breaking point scenario

Credible N-2 contingency for breaking point scenario Credible N-2 Contingency (After outages of Naughton – Ben Lomond 230kV line & Birch Creek – Ben Lomond 230kV line) Credible N-2 contingency for breaking point scenario Loads to 100 % of 30-minute emergency rating on Silver Creek – Snyderville 138kV line

Pre-contingency (Before outages of Naughton – Ben Lomond 230kV line & Birch Creek – Ben Lomond 230kV line) Normal (N-0) during light load & 1200 MW of new Evanston West – worst scenario

Credible N-2 contingency for worst scenario Credible N-2 Contingency (After outages of Naughton – Ben Lomond 230kV line & Birch Creek – Ben Lomond 230kV line) Credible N-2 contingency for worst scenario Loads to 145 % of 30-minute emergency rating on Silver Creek – Snyderville 138kV line Loads to 115 % of 30-minute emergency rating on Snyderville – Snyderville Tap138kV line Loads to 135 % of 30-minute emergency rating on Snyderville Tap – Cottonwood138kV line Loads to 105 % of 30-minute emergency rating on Naughton – Treasureton 230kV line

Total Amount of Generation Tripping Required *Naughton – Treasureton 230kV, Naughton – Ben Lomond 230kV, Birch Creek – Ben Lomond 230kV & Railroad – Croydon 138kV lines

Induced Equation for Total Amount of Generation Tripping Required Total amount of generation tripping = 1.04 x flow of new Evanston West path – 810 MW

Summary for Credible N-2 Contingency of Naughton – Ben Lomond 230kV line & Birch Creek – Ben Lomond 230kV line Breaking point Light load & 820 MW flow on new Evanston West Mitigation Trip up to 610 MW of Southwest Wyoming generators To prevent generation over-tripping, the following equation will be applied: Gen tripping amount = 1.04 x flow of new Evanston West – 810 MW New RAS set-up for outages of Naughton – Ben Lomond 230kV line & Birch Creek – Ben Lomond 230kV line Arm RAS when 800 MW flows on new Evanston West path – margin considered Trip up to 610 MW of the southwest Wyoming generators in order of: Mountain wind – tripping up to 140 MW Hinshaw wind – tripping up to 140 MW Naughton coal generation #2 – tripping up to 225 MW (OR Naughton coal generation #3 – tripping up to 330 MW)

Naughton RAS (SW WY Generation Tripping Scheme) Diagram for Outages of Naughton – Ben Lomond 230kV line & Birch Creek – Ben Lomond 230kV line

New Naughton RAS (SW WY Generation Tripping Scheme) Classification This RAS results in Up to 610 MW generation tripping No load losses Misoperation or failure of this RAS will result in thermal overloads on the southwest Wyoming and Park City transmission system. Manual operation to reduce the southwest Wyoming generation output or back down the new Evanston West flow by adjusting the Monument phase shifting transformers Failure of this RAS will not result in cascading and impact will be limited to southwest Wyoming and Park City areas only. Therefore, Naughton RAS (SW WY Generation Tripping Scheme) is classified as LAPS.

Necessity for new modified RAS Additional redundant communication channel for Railroad – Croydon 138 kV line to monitor flow of new Evanston West path Remove one of the existing credible N-2 (outages of Naughton – Ben Lomond 230kV & Naughton – Birch Creek 230kV lines) from Naughton RAS (SW WY Generation Tripping Scheme) according to new credible N-2 criteria Update the existing RAS

Heads-up for Future Transmission System New addition Jordanelle – Midawy138kV line (expected in-service date: December 2019) Update the modified RAS With the addition of the new Jordanelle – Midway 138kV line, the Naughton RAS (SW WY Generation Tripping Scheme) needs to be remodified.

Naughton RAS (SW WY Generation Tripping Scheme) – LAPS PacifiCorp requests WECC RASRS accept the modified Naughton RAS (SW WY Generation Tripping Scheme) as a LAPS.

Questions?