Transmission Tot 3 Information

This Path Rating (Tot Description) is provided for information only and is not to be considered as an official copy. The official Path Ratings are maintained by the Western Systems Coordinating Council (WSCC) and can be requested from their web site at www.wscc.com.

Location: Border between Northeast Colorado and Southeast Wyoming

Definition: Sum of the flows on the following transmission lines:

Line: Metered End:

Archer-Ault 230kV Archer

Laramie River-Ault 345kV Laramie River

Laramie River-Story 345kV Laramie River

Cheyenne-Rockport 115kV Cheyenne

Sidney-Sterling 115kV Sidney

Sidney-N. Yuma 230kV Sidney

Transfer Limit: North to South: 1509 MW (Maximum)

South to North Not defined

Depending on local generation levels, DC tie levels and direction, the real-time rating can range between a maximum of 1509 MW and a minimum of 663 MW. Typically, the real-time rating is calculated dynamically and updated every minute based on Table 1A.

Critical Disturbance that limits the transfer capability: The critical disturbances and limiting elements vary with the various scenarios. Reference Table 1A for further information.

When: Rating was first established in 1981. The current rating was established in
July 1999 with publication of the “Comprehensive Progress Report for the
Revised Rating of the TOT 3 Transfer Path.” The study was conducted by
Western and the revised rating was jointly proposed by:
Western Area Power Administration (WAPA) - Loveland
Tri-State Generation & Transmission Association, Inc. (TSGT)
Public Service Company of Colorado (PSC)
Basin Electric Power Cooperative (BEPC)

System Conditions: This rating is independent of transfer levels between major areas of WSCC. The transfer limit is impacted by local area generation and the direction and magnitude of DC tie flows. Historically, the flows have all been north to south across the path. Under certain operating conditions, when TOT 3 is loaded to its limit, the TOT 5 capability cannot be used since additional schedule on TOT 5 will overload TOT 3.

Study Criteria: (Summary)
System intact:

Per unit voltages between 0.95 p.u. and 1.05 p.u.

All line and transformers loaded to less than continuous rating.

Single contingency outage conditions:

Per unit voltages between 0.90 p.u. and 1.10 p.u.

All lines loaded to less than 15 minute emergency ratings.

All transformers loaded to less than 30 minute emergency ratings.

Transient voltage swings down to 0.7 p.u. permitted.

Remedial Actions Required: Remedial actions are required to achieve the rated transfer capability. Following an outage, all overloaded lines and transformers must have their loadings reduced to continuous ratings within 15 minutes. This is accomplished by reducing schedules and adjusting generation.

Formal Operating Procedure: There is a formal operating procedure dated November 1999. WAPA-Loveland is the operating agent and uses real-time flows to monitor the path.

Allocation: The transfer capability of the path is divided between WAPA, Missouri
Basin Power Project (MBPP), Public Service Company of Colorado (PSC), and Tri-State Generation & Transmission (TSGT). TSGT and BEPC are members of MBPP.

Interaction w/Other Transfer Paths that would Reduce the Capability of this path: None.

Contact Person: Thu-Hong Tran
Western Area Power Administration
Rocky Mountain Region
P. O. Box 3700
Loveland, CO 80539-3003
(303) 490-7404
(303) 490-7213 - fax
trant@wapa.gov

TABLE 1A
TOT3 SYSTEM INTACT LIMITS
1999 HEAVY SPRING
Pawnee-Story at 625 MVA emergency rating - Rawhide at 720 MW - Wray Transformer is out of service.
DC Ties

300 MW East to West 0 MW 300 MW West to East

LRS 1100 MW
Pawnee 495 MW 1a1a18
New TOT3 = 1509
(Outage Pawnee-Story loded Gary-Woodrow at 100% normal rating 109 MVA)
1a1b21
New TOT3 = 1412 MW
(Outage Pawnee-Story loaded Gary-Woodrow at 100% of normal rating 109 MVA & Alvin 115 KV bus at 0.9 p.u. during LRS-Ault outage)
1a1c21
New TOT3 = 1165 MW
(Outage LRS-Story loaded Sidney-Stegall at 100% of normal rating)

LRS 550 MW
Pawnee 495 MW 1b1a19
New TOT3 = 1233 MW
(Outage Sidney-N. Yuma loaded Peetz-Sidney at 100% of normal rating 109 MVA)
1b1b21
New TOT3 = 1129 MW
(Sidney 115 bus at 0.9 during Sidney Transformer outage)
1b1c17
New TOT3 = 899 MW
(Outage Stegall-DJ loaded LRS-DJ at 100% of nominal rating 441 MVA)

LRS 1100 MW
Pawnee 0 MW 1a2a3
New TOT3 = 1352 MW
(Outage Sidney-N. Yuma loaded Peetz-Sidney at 100% of normal rating 109 MVA)
1b2b12
New TOT3 = 1311 MW
(Outage LRS-Ault loaded Pawnee-Story 108% of emergency rating 625 MVA)
1a2c9
New TOT3 = 1179 MW
(Outage LRS-Ault loaded Sidney-Stegall at 100% of nominal rating)

LRS 550 MW
Pawnee 0 MW 1b2a6
New TOT3 = 1113MW
(Outage Sidney-N. Yuma loaded Peetz-Sidney at 100% of normal rating 109 MVA)
1b2b12
New TOT3 = 1133 MW
(Sidney 115 bus at 0.9 during Sidney Transformer outage)
1b2c9
New TOT3 = 918 MW
(Outage Stegall-DJ loaded LRS-DJ at 100% of nominal rating 441 MVA)

Transmission Area Map
RMA OASIS Home Page

	300 MW East to West	0 MW	300 MW West to East
LRS 1100 MW Pawnee 495 MW	1a1a18 New TOT3 = 1509 (Outage Pawnee-Story loded Gary-Woodrow at 100% normal rating 109 MVA)	1a1b21 New TOT3 = 1412 MW (Outage Pawnee-Story loaded Gary-Woodrow at 100% of normal rating 109 MVA & Alvin 115 KV bus at 0.9 p.u. during LRS-Ault outage)	1a1c21 New TOT3 = 1165 MW (Outage LRS-Story loaded Sidney-Stegall at 100% of normal rating)
LRS 550 MW Pawnee 495 MW	1b1a19 New TOT3 = 1233 MW (Outage Sidney-N. Yuma loaded Peetz-Sidney at 100% of normal rating 109 MVA)	1b1b21 New TOT3 = 1129 MW (Sidney 115 bus at 0.9 during Sidney Transformer outage)	1b1c17 New TOT3 = 899 MW (Outage Stegall-DJ loaded LRS-DJ at 100% of nominal rating 441 MVA)
LRS 1100 MW Pawnee 0 MW	1a2a3 New TOT3 = 1352 MW (Outage Sidney-N. Yuma loaded Peetz-Sidney at 100% of normal rating 109 MVA)	1b2b12 New TOT3 = 1311 MW (Outage LRS-Ault loaded Pawnee-Story 108% of emergency rating 625 MVA)	1a2c9 New TOT3 = 1179 MW (Outage LRS-Ault loaded Sidney-Stegall at 100% of nominal rating)
LRS 550 MW Pawnee 0 MW	1b2a6 New TOT3 = 1113MW (Outage Sidney-N. Yuma loaded Peetz-Sidney at 100% of normal rating 109 MVA)	1b2b12 New TOT3 = 1133 MW (Sidney 115 bus at 0.9 during Sidney Transformer outage)	1b2c9 New TOT3 = 918 MW (Outage Stegall-DJ loaded LRS-DJ at 100% of nominal rating 441 MVA)

Location:	Border between Northeast Colorado and Southeast Wyoming
Definition:	Sum of the flows on the following transmission lines:
	Line:	Metered End:
	Archer-Ault 230kV	Archer
	Laramie River-Ault 345kV	Laramie River
	Laramie River-Story 345kV	Laramie River
	Cheyenne-Rockport 115kV	Cheyenne
	Sidney-Sterling 115kV	Sidney
	Sidney-N. Yuma 230kV	Sidney
Transfer Limit:	North to South:	1509 MW (Maximum)
	South to North	Not defined
	Depending on local generation levels, DC tie levels and direction, the real-time rating can range between a maximum of 1509 MW and a minimum of 663 MW. Typically, the real-time rating is calculated dynamically and updated every minute based on Table 1A.
Critical Disturbance that limits the transfer capability:	The critical disturbances and limiting elements vary with the various scenarios. Reference Table 1A for further information.
When:	Rating was first established in 1981. The current rating was established in July 1999 with publication of the “Comprehensive Progress Report for the Revised Rating of the TOT 3 Transfer Path.” The study was conducted by Western and the revised rating was jointly proposed by: Western Area Power Administration (WAPA) - Loveland Tri-State Generation & Transmission Association, Inc. (TSGT) Public Service Company of Colorado (PSC) Basin Electric Power Cooperative (BEPC)
System Conditions:	This rating is independent of transfer levels between major areas of WSCC. The transfer limit is impacted by local area generation and the direction and magnitude of DC tie flows. Historically, the flows have all been north to south across the path. Under certain operating conditions, when TOT 3 is loaded to its limit, the TOT 5 capability cannot be used since additional schedule on TOT 5 will overload TOT 3.
Study Criteria:	(Summary) System intact: Per unit voltages between 0.95 p.u. and 1.05 p.u. All line and transformers loaded to less than continuous rating. Single contingency outage conditions: Per unit voltages between 0.90 p.u. and 1.10 p.u. All lines loaded to less than 15 minute emergency ratings. All transformers loaded to less than 30 minute emergency ratings. Transient voltage swings down to 0.7 p.u. permitted.
Remedial Actions Required:	Remedial actions are required to achieve the rated transfer capability. Following an outage, all overloaded lines and transformers must have their loadings reduced to continuous ratings within 15 minutes. This is accomplished by reducing schedules and adjusting generation.
Formal Operating Procedure:	There is a formal operating procedure dated November 1999. WAPA-Loveland is the operating agent and uses real-time flows to monitor the path.
Allocation:	The transfer capability of the path is divided between WAPA, Missouri Basin Power Project (MBPP), Public Service Company of Colorado (PSC), and Tri-State Generation & Transmission (TSGT). TSGT and BEPC are members of MBPP.
Interaction w/Other Transfer Paths that would Reduce the Capability of this path:	None.
Contact Person:	Thu-Hong Tran Western Area Power Administration Rocky Mountain Region P. O. Box 3700 Loveland, CO 80539-3003 (303) 490-7404 (303) 490-7213 - fax trant@wapa.gov