1. Comanche-Walsenburg RAS Input Modification
August 1st, 2017

2. Background
Tri-State’s Operation, Engineering, and Protection group initiated a project to modify the Comanche-Walsenburg 230 kV RAS inputs to address unintentional activation due to breaker switching for breaker/relay testing.

3. System Overview
Comanche

4. System Overview

5. Comanche-Walsenburg RAS
Classification: LAPS
Function: Mitigate overload of parallel 115 kV line
Input: Comanche-Walsenburg 230 kV line status
Output: Trip Walsenburg-Gladstone 230 kV
5-second delay for reclosing coordination

6. Comanche-Walsenburg RAS
Loss of
Comanche-Walsenburg 230 kV
Trip Gladstone-Walsenburg 230 kV

7. Comanche-Walsenburg RAS

8. Other RAS’s in Area
Three (3) RAS’s on the Comanche-Walsenburg-Gladstone 230 kV Path:
Comanche-Walsenburg RAS
Trips Walsenburg-Gladstone for loss of Comanche Walsenburg
Walsenburg-Gladstone RAS
Reduces Northeast New Mexico load fed from Gladstone/Clapham for loss of 230 kV path into Gladstone
WECC-1
Trip Gladstone PST

9. Existing RAS Operation
Comanche-Walsenburg 230 kV line status is detected via 52b contacts in the terminal breakers.
Using 52b contacts has resulted in unintentional tripping when operating Breaker XFER switch.

10. Coordination
5.0-second delay was based on reclosing coordination on Comanche-Walsenburg 230.
Walsenburg Terminal: 1-shot, operates at 63-cycles after line opening.
Comanche Terminal: 1-shot, operates at 20-cycles after line opening. Currently disabled.
Tri-State OPS is working with Xcel to re-enable.
Proposal: Decrease RAS Time Delay to 2-seconds to coordinate with reclosing.

11. Proposed RAS Operation
RAS Inputs:
Add Walsenburg-Stem Beach 115 (as measured at Walsenburg) to input logic
351 Amps (70 MVA)
Non-Directionalized
RAS Time Delay decreased to 2-second from 5-seconds

12. Proposed RAS Operation
Monitor Walsenburg-Stem Beach 115 kV
Line Current: 351 Amps
Trip Delay reduced to
2-seconds from 5-seconds

13. Proposed RAS Operation
The new input supervises the RAS.
Increases security
Increases system reliability by eliminating trips deemed unnecessary due to loading conditions.
The 5-second delay is not appropriate given the speed of reclosing.

14. 351 Amp Determination

15. 351 Amp Determination
351 Amp (70 MVA) set-point was determined using a 4-variable load/flow matrix.
Loads: Pueblo Tap, Stem Beach, Walsenburg
Flow: Walsenburg-Gladstone 230 (Gladstone PST)
Loads/Flow varied from historical minimum to maximum and 10-year forecast under the following outages:
All lines in-service
Comanche-Walsenburg 230 out-of-service
Both Walsenburg 230/115 XMFRs out-of-service

16. 351 Amp Determination Approximately 3,000 load/flow matrix cells
Identified 351 Amps (70 MVA) as the optimal set-point given load forecasts and historical loading data.

17. Existing Config. - Primary

18. Existing Config. - Backup

19. Proposed Changes - Primary

20. Proposed Changes - Backup

21. Proposed Changes - Primary

22. Tri-State is requesting that RASRS approve the Comanche-Walsenburg RAS logic change and reduced time delay.

23. Questions?