Path Rating Catalog 2013 - Western Electricity Coordinating Council

Revised January 2013
III-3. Montana Alberta Tie Line
Accepted Rating
Existing Rating
Location:
Between Lethbridge, Alberta and Great Falls, Montana
Other
Definition: The Montana-Alberta Tie-Line (MATL) transmission project is a 230-
kilovolt (KV), 330 megavolt ampere (MVA) electrical transmission line
allowing for movement of power between Alberta and Montana. The
project consists of a new substation in Alberta, located approximately 15
km north of the City of Lethbridge, Alberta that ties into the existing 240
kV Alberta Interconnected Electric System (AIES) system. A phase
shifting transformer will be installed to control flows both north and south
and to step the voltage up from the transmission line voltage of 230 kV to
the Alberta nominal system voltage of 240 kV. A mid-point substation
named Marias will be built approximately 10 km south of the town of Cut
Bank, Montana and will contain Series Capacitors (SC) facing south for
voltage support. A Hay Lake substation approximately 41 km north of
Marias will be a connection point for the proposed wind generation project.
This site will also contain SC facing north. At the south end, the MATL
transmission line will terminate at the existing Great Falls, Montana, 230
kV substation.
Transfer Limit: 325 MW N to S and 300 MW S to N metered at MATL 120S substation.
The S to N limit is valid with and without wind generation at Hay Lake.
Because studied deliveries to Great Falls did not exceed 300 MW, the N to
S transfer capability (metered at MATL 120S substation) when wind
generation is present at Hay Lake needs to be reduced by approximately
one MW for each MW of generation that is on-line at Hay Lake.
Critical
Disturbance
that limits the
transfer
capability:
When:
System
Conditions:
None. The non-simultaneous limit is determined by the steady state thermal
rating of the MATL
Phase shifting transformer.
On August 28, 2007 MATL achieved Phase 3 status with an Accepted Path
Rating of 325 MW north to south and 300 MW south to north (metered at
MATL 120S) for its tie line, without any generation interconnected. On
October 9, 2009, MATL provided notification that it was amending the
WECC Accepted Path Rating of the MATL project to include 300 MW of
wind generation connected at Hay Lake substation. Following the
expression of interest period, a Project Review Group (PRG) was formed to
aid with scope preparation and to oversee the execution of the study of the
addition of the wind generation to the MATL project. The objective of this
new study as stated in the August 2010 study scope was to determine if the
generation connection detrimentally impacts the current Accepted Path
Rating, and if it does, what mitigation will be needed to maintain the
Accepted Path Rating. This study work was concluded and MATL received
accepted Phase 3 rating 325 MW north-to-south and 300 MW south-tonorth
on November 30, 2012.
For the original 2007 studies, heavy summer and light spring conditions
were studied for the non-simultaneous analysis. For the Path 1
PART VI Item 1-216