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

2. 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.

3. 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.

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

5. 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

6. 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

7. 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

8. 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

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

10. 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

11. 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)

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

13. 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.

14. 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

16. 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.

17. 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.

18. Questions?