Path Rating Catalog 2013 - Western Electricity Coordinating Council

Revised January 2013
III-13. Midpoint West Upgrade
(Gateway West)
Accepted Rating
Existing Rating
Other
Location:
Definition:
Transfer Limit:
Critical
Disturbance
that limits the
transfer
capability:
When:
System
Conditions:
Study Criteria:
Remedial
Actions
Required:
Southeast Idaho
Sum of the flows on the following lines:
Line
Midpoint-Hemingway 500 kV
Cedar Hill-Hemingway 500 kV
Midpoint-Boise Bench 230 kV
Midpoint-Rattlesnake 230 kV
Justice-Dram 230 kV
L Malad-Mt Home 138 kV
U Salmon-Mt Home 138 kV
Metered End
Midpoint
Cedar Hill
Midpoint
Midpoint
Justice
L Malad
U Salmon
East to West: 4400 MW (Gateway West Stage One)
West to East: Not rated
With the Gateway West Project (Stage 1), the Midpoint West 4400 MW
transfer capacity is limited by the (N-1) loss of the Populus-Cedar Hill-
Hemingway 500 kV line (5% post-transient reactive margin) and the double
line (N-2) loss of Midpoint-Hemingway 500 kV and Midpoint-King 230 kV
lines (thermal – Midpoint 230 kV series capacitors) or N-2 loss of the
Midpoint-Hemingway 500 kV and Midpoint 500/345 kV transformer due to
breaker failure (2.5% post-transient reactive margin).
The increase in transfer rating for the Midpoint West path entered Phase 2 on
February 6, 2009 as part of the Gateway West Project, and achieved Phase 3
status on July 21, 2011 with an Accepted Rating of 4400 MW.
The Midpoint West transfer rating with the Gateway West Project (Stage 1)
was determined with simultaneous heavy transfers on series path (Path C
south to north, Bridger West, Borah West, and Idaho-Northwest with the
Boardman-Hemingway 500 kV project) consistent with the transfers of
eastern thermal and alternative renewable resources to the west.
NERC/WECC Planning Standards
Remedial action schemes (RAS) will be required to achieve the increase
Midpoint West rating and will initiate one or more of the following Remedial
Actions:
Tripping of one/two Jim Bridger unit(s).
Bypassing either or both Midpoint and/or Burns 500 kV
Series Capacitors.
Insertion of one or more of the Kinport, Borah, and Midpoint 345 kV
Shunt Capacitors.
Insertion of one or more of the Midpoint and Hemingway 500 kV
Shunt Capacitors.
PART VI Item 1-242