Path Rating Catalog 2013 - Western Electricity Coordinating Council

16. Idaho - Sierra
Revised December 2010
Accepted Rating
Existing Rating
Other
Location:
Definition:
Transfer Limit:
Critical
Disturbance
that limits the
transfer
capability:
When:
System
Conditions:
Study Criteria:
Remedial
Actions
Required:
Formal
Operating
Procedure:
Allocation:
Interaction
w/Other
Transfer Paths:
Border between southern Idaho and northern Nevada
Midpoint (Idaho Power Co.) – Humboldt (SPPC) 345 kV line. The metering
point is considered to be at the Idaho-Nevada border
North to South: 500 MW
South to North: 360 MW
The capacities listed above are non-simultaneous ratings of the line.
Simultaneous ratings are dependent on Sierra’s net control area operations.
Seasonal System Operating Limits (SOLs) may be more restrictive for
operating South to North.
Outage of the Humboldt-Coyote Creek 345 kV line which overloads the
Humboldt 345/120 kV transformer, is a critical disturbance which determines
the North to South rating. The South to North rating is determined by both
outages of the Coyote Creek-Valmy and/or Coyote Creek-Humboldt 345 kV
lines and following thermal overloads of the 345/120 transformers and
underlying 120 kV system..
Initial non-simultaneous transfer studies were performed jointly by Sierra
Pacific Power Company and Idaho Power Company in 1980. Periodically,
Sierra updates their net system import limit studies to quantify simultaneous
limits.
Studies of the Sierra net system import limit have been conducted for all
seasons and at various load levels.
Criteria used in determining Sierra’s net import and export limits:
• The post disturbance steady state voltages on the Ft. Churchill-Pavant
230 kV load buses must recover to 90% of pre-disturbance voltage and no
less than 0.90 p.u. Automatic reactor switching allowed.
• The post disturbance net flow on the Sierra-PG&E 120 kV and 60 kV
interties must not exceed the limitations on that intertie (nominally
180 MW).
None
None
The transfer capability of the path is allocated as follows:
Ownership
Allocation
50% Idaho 100% North-bound capacity
50% Sierra 100% South-bound capacity
Sierra’s system import and export limits and the flows on their other tie lines
affect the scheduling capability of this intertie.
PART VI Item 1-43