Path Rating Catalog 2013 - Western Electricity Coordinating Council

25. PacifiCorp/PG&E
115 kV Interconnection
Revised January 2013
Accepted Rating
Existing Rating
Other
Location: Southern Oregon/Northern California (Line 14)
Definition:
Sum of flow on Line 14, measured at Cascade.
Transfer Limit: Winter Summer
North to South: 100 MW * 80 MW
South to North: 45 MW ** 45 MW **
The thermal rating of this 115 kV line is 100/149 MVA Summer/Winter
(397.5 ACSR conductor).
Critical
Disturbance
that limits the
transfer
capability:
When:
System
Conditions:
Study Criteria
* Due to load growth in the area, there are periods when the winter transfer
limit may be reduced below 100 MW, sometimes as low as 80 MW.
** The south to north non-simultaneous rating listed in the WECC Transfer
Capability Diagram is 45 MW. This capability is rated under tie-line open
south of phase shifter and is equivalent to the magnitude of PacifiCorp’s local
area load.
Path rating was established on April 19, 1984 with the publishing of the
WECC progress report, by project owners.
The powerflow and stability studies deriving the path rating, above, were
conducted by PacifiCorp and PG&E.
This interconnection operates in parallel with the California-Oregon Intertie
(COI). In order to direct flow of the 100 MW south on Line 14, a
75/100/125 MVA, 118 kV 0-60 degrees compensated phase shifter is
installed at PacifiCorp’s Weed Junction substation, Weed Junction,
California. This phase-shifting transformer regulates the flow of power,
preventing power scheduled over it from flowing on the COI.
The following stability simulations were made:
A. Islanding Without the Line 14, 115 kV Tie
This simulation assumes 3200 MW on the COI as well as 4163 MW on
the Arizona to southern California path and indicates that minimum
standards for stable operation can be achieved, complying with WECC
criteria. Stability plot of the Devers 500 kV bus shows oscillations of
increasing amplitude through the first 7-8 seconds, with decreasing
amplitude thereafter.
The minimum transient swing voltage was at the Devers 230 kV bus with
81.7%. Use of the SDG&E’s Damping Coefficient Method demonstrates
a 7.6% damping on this bus. Frequencies drop to 58.84 Hz minimum in
California causing some under-frequency load shedding.
PART VI Item 1-70