Transmission Tot 1A 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 Northwest Colorado

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

Line: Metered End:

Bears Ears - Bonanza 345kV Bears Ears

Hayden - Artesia 138kV Hayden

Meeker - Rangely 138kV Rangely

Transfer Limit: East to West 650 MW (Maximum)

West to East Not defined

Depending on local generation levels and the flows on underlying 115kV and 138kV facilities, the real time rating can range between a minimum of 230MW and a maximum of 650MW (Reference Attachment 1.) Typically, the real time rating centers around 550MW.

Critical Disturbance that limits the transfer capability: Outage of the Bears Ears - Bonanza 345kV line. The limiting element can be the emergency overload on the Upalco - Carbon 138kV line, the Flaming Gorge 230/138kV transformer, the Hayden - Artesia 138kV line, or the Meeker - Rangely 138kV line (Reference Attachment 1.)

When: Rating established in March 1990 with the publication of "Bears Ears - Bonanza 345kV Line Operating Study Report." The operating study was conducted jointly by:

Western Area Power Administration - Salt Lake, Golden, Montrose

Tri-State Generation and Transmission Cooperative

Utah Associated Municipal Power System

Platte River Power Authority

Deseret Generation and Transmission Cooperative

Salt River Project

Utah Power & Light Co. (now PacifiCorp)

Colorado-Ute Electric Association (now TSGT and Public Service Company of Colorado)

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

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 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, except PacifiCorp which is limited to 0.85 p.u. and DG&T Rangely bus which is limited to 0.75 p.u.

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 or lowering local generation. Unit trip schemes are implemented for Bonanza and Flaming Gorge generation for outages of the Bonanza-Mona 345kV line. Remedial action schemes are required to achieve the rated transfer capability.

Format Operating Procedure: There is a formal operating procedure dated July 26, 1990. 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, PRPA, TSGT, and UAMPS.

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

Attachment 1

TRANSFER CAPABILITY ALGEBRAIC EXPRESSIONS
TOT 1A transfer (schedule) limit is equal to
The lesser of
1 - TOT 1A limit based on Upalco-Carbon limit due to
    Bonanza-Mona outage
TOT 1A = UPC>CBNlf + 5.4(145 - UPC>CBNlf) + .886(BNZg)
                + .52(FGg) + NET INTERCHANGE + VNL>FGlf
2 - TOT 1A limit based on Flaming Gorge 138/230
    Transformer limit due to Bonanza-Mona outage
TOT 1A = UPC>CBNlf + 4.5(200 - FGxf) + 1.13(BNZg)
                + 2.74(FGg) + NET INTERCHANGE + VNL>FGlf
3 - TOT 1A limit based on Hayden-Artesia or Meeker-Rangely
    limit due to a Bears Ears-Bonanza outage
Hayden-Artesia
TOT 1A = MKR>SWRlf + HDN>ARTlf + 7.0(140 - HDN>ARTlf)
Meeker-Rangely
TOT 1A = MKR>SWRlf + HDN>ARTlf + 4.9(160 - MRK>SWRlf)
Where
BNZg = Droppable Bonanza generation
FGg = Droppable Flaming Gorge generation
MRK>SWRlf = Meeker-Southwest Rangely line flow
HDN>ARTlf = Hayden-Artesia line flow
VNL>FGlf = Vernal-Flaming Gorge 1 & 2 line flows
UPC>CBNlf = Upalco-Carbon line flow
FGxf = Flaming Gorge 138/230 1 & 2 transformer flows
140 = Hayden-Artesia emergency rating
160 = Meeker-Rangely emergency rating
250 = Flaming Gorge transformers emergency rating
145 = Upalco-Carbon emergency rating

Transmission Area Map
RMA OASIS Home Page

Location:	Extreme Northwest Colorado
Definition:	Sum of the flows on the following transmission lines:
	Line:	Metered End:
	Bears Ears - Bonanza 345kV	Bears Ears
	Hayden - Artesia 138kV	Hayden
	Meeker - Rangely 138kV	Rangely
Transfer Limit:	East to West	650 MW (Maximum)
	West to East	Not defined
	Depending on local generation levels and the flows on underlying 115kV and 138kV facilities, the real time rating can range between a minimum of 230MW and a maximum of 650MW (Reference Attachment 1.) Typically, the real time rating centers around 550MW.
Critical Disturbance that limits the transfer capability:	Outage of the Bears Ears - Bonanza 345kV line. The limiting element can be the emergency overload on the Upalco - Carbon 138kV line, the Flaming Gorge 230/138kV transformer, the Hayden - Artesia 138kV line, or the Meeker - Rangely 138kV line (Reference Attachment 1.)
When:	Rating established in March 1990 with the publication of "Bears Ears - Bonanza 345kV Line Operating Study Report." The operating study was conducted jointly by: Western Area Power Administration - Salt Lake, Golden, Montrose Tri-State Generation and Transmission Cooperative Utah Associated Municipal Power System Platte River Power Authority Deseret Generation and Transmission Cooperative Salt River Project Utah Power & Light Co. (now PacifiCorp) Colorado-Ute Electric Association (now TSGT and Public Service Company of Colorado)
System Conditions:	This rating is independent of transfer levels between major areas of WSCC, although the actual flow is heavily impacted by east to west inadvertent. The transfer limit is impacted by local area generation and load levels. Historically, the flows have all been east to west across the path.
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 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, except PacifiCorp which is limited to 0.85 p.u. and DG&T Rangely bus which is limited to 0.75 p.u.
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 or lowering local generation. Unit trip schemes are implemented for Bonanza and Flaming Gorge generation for outages of the Bonanza-Mona 345kV line. Remedial action schemes are required to achieve the rated transfer capability.
Format Operating Procedure:	There is a formal operating procedure dated July 26, 1990. 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, PRPA, TSGT, and UAMPS.
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