Transmission Tot 2A 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: Extreme southwest Colorado

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

Line: Metered End:

Hesperus-San Juan 345kV San Juan

Durango-Glade Tap 115 kV Glade Tap

Lost Canyon-Shiprock 230kV Shiprock

Transfer Limit: North to South: 690 MW minus net load in the Montrose-Curecanti-San
Juan-Shiprock area of southwest Colorado. The load itself ranges 110-220 MW, and internal thermal generation can be 100 MW and hydro generation can be 15 MW. However, the maximum rating is 690 MW.

South to North Not defined

Depending on local load and generation levels, the real time rating ranges between a maximum of 690MW and a minimum of 550MW. Typically, the real time rating centers around 650MW.

Critical Disturbance: The critical disturbance is the outage of the 345kV system between Montrose and San Juan. The limiting elements are low voltages or emergency overloads on the local 115kV system, or emergency overloads on local 230/115kV or 138/115kV transformers. The specific outage and limiting element depend on load levels and generation patterns.

When: The rating was established jointly by Colorado-Ute Electric Association (CUEA) and Western Area Power Administration (WAPA)-Montrose, in 1989.

System Conditions: This rating is independent of transfer levels between major areas of WSCC although the actual flow is heavily impacted by inadvertent. The transfer limit is impacted by local area generation and load levels. Historically, the flows have been predominately north to south across the path, although flows south to north have been recently experienced.

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 down to 0.7 p.u. permitted.

Remedial Actions Required: Remedial action schemes 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, lowering local generation or manually tripping a lower voltage parallel path. For the Montrose-Hesperus 345kV line outage with generation at Nucla above 60MW, the parallel Montrose-Nukla 115kV line can be automatically transfer tripped. This automatic transfer trip scheme is normally enabled. If it is disabled, then real time transfer capability limits are calculated using local load and local generation as input variables.

Formal Operating Procedures: There is a formal operating procedure, in the form of a letter agreement between CUEA and WAPA, dated June 1, 1989. WAPA-Montrose is the operating agent, and uses real time flows to monitor the path.

Allocation: The transfer capability of the path is divided between WAPA, Public Service
Company of Colorado and Tri-State G&T.

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

Contact Person: Brent Vossler
Western Area Power Administration
Rocky Mountain Region
P. O. Box 3700
Loveland, CO 80539-3003
(970) 490-7482
(970) 490-7213 - fax
avossler@wapa.gov

PSCO TOT2A Capacity:   9/11/01
As portrayed below, there are a number of facilities that effect PSCO's TOT2A
capacity allocation. The numbers below all represent the PSCO allocation
when Nucla Generating Station is operating. If Nucla is off, then all of the
allocations are further reduced.

TOT2A Prior Outage Lists and PSCO Allocation:
(The numbers below represent only PSCO's share of North to South Capability
derived from system studies. They are all subject to change based on actual
system conditions, notably including changes in load in SW Colorado)
                                                                            PSCO
                                                                            -MW-
System Intact Average Capability Limit                    129
Forced Outage                                                    PSCO
Montrose-Hesperus 345 kV Line                             39
Hesperus-San Juan Line 345 kV Line                       32
Curecanti-Lost Canyon 230 kV Line                        74
Lost Canyon-Shiprock 230 kV Line                         75
Ute Grand Junction-Montrose 115 kV Line              98
Lost Canyon-Cahone 115 kV Lines                         106
Lost Canyon-Durango 115 kV Line                          98
Nucla-Cahone 115 kV Line                                     100
Nucla-Montrose 115 kV Line                                  108

Planned Outage *                                               PSCO
Montrose-Hesperus 345 kV Line                             14
Hesperus-San Juan Line 345 kV Line                       5
Curecanti-Lost Canyon 230 kV Line                        129
Lost Canyon-Shiprock 230 kV Line                         129
Ute Grand Junction-Montrose 115 kV Line              49
Lost Canyon-Cahone 115 kV Lines                         69
Lost Canyon-Durango 115 kV Line                         49
Nucla-Cahone 115 kV Line                                     54
Nucla-Montrose 115 kV Line                                  74

* The 1st 8 hours of all planned outages are considered forced outage

Transmission Area Map
RMA OASIS Home Page

Location:	Extreme southwest Colorado
Definition:	Sum of the flows on the following transmission lines:
	Line:	Metered End:
	Hesperus-San Juan 345kV	San Juan
	Durango-Glade Tap 115 kV	Glade Tap
	Lost Canyon-Shiprock 230kV	Shiprock
Transfer Limit:	North to South:	690 MW minus net load in the Montrose-Curecanti-San Juan-Shiprock area of southwest Colorado. The load itself ranges 110-220 MW, and internal thermal generation can be 100 MW and hydro generation can be 15 MW. However, the maximum rating is 690 MW.
	South to North	Not defined
	Depending on local load and generation levels, the real time rating ranges between a maximum of 690MW and a minimum of 550MW. Typically, the real time rating centers around 650MW.
Critical Disturbance:	The critical disturbance is the outage of the 345kV system between Montrose and San Juan. The limiting elements are low voltages or emergency overloads on the local 115kV system, or emergency overloads on local 230/115kV or 138/115kV transformers. The specific outage and limiting element depend on load levels and generation patterns.
When:	The rating was established jointly by Colorado-Ute Electric Association (CUEA) and Western Area Power Administration (WAPA)-Montrose, in 1989.
System Conditions:	This rating is independent of transfer levels between major areas of WSCC although the actual flow is heavily impacted by inadvertent. The transfer limit is impacted by local area generation and load levels. Historically, the flows have been predominately north to south across the path, although flows south to north have been recently experienced.
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 down to 0.7 p.u. permitted.
Remedial Actions Required:	Remedial action schemes 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, lowering local generation or manually tripping a lower voltage parallel path. For the Montrose-Hesperus 345kV line outage with generation at Nucla above 60MW, the parallel Montrose-Nukla 115kV line can be automatically transfer tripped. This automatic transfer trip scheme is normally enabled. If it is disabled, then real time transfer capability limits are calculated using local load and local generation as input variables.
Formal Operating Procedures:	There is a formal operating procedure, in the form of a letter agreement between CUEA and WAPA, dated June 1, 1989. WAPA-Montrose is the operating agent, and uses real time flows to monitor the path.
Allocation:	The transfer capability of the path is divided between WAPA, Public Service Company of Colorado and Tri-State G&T.
Interaction w/Other Transfer Paths that would Reduce the Capability of this path:	None.
Contact Person:	Brent Vossler Western Area Power Administration Rocky Mountain Region P. O. Box 3700 Loveland, CO 80539-3003 (970) 490-7482 (970) 490-7213 - fax avossler@wapa.gov

Transmission Area Map RMA OASIS Home Page

Transmission Area Map
RMA OASIS Home Page