20180208PAC to Staff Path 18 Overload Mitigation RAS - Assessment.docx

PacifiCorp Main Grid Planning
PRC-(012 through 014)-WECC-CRT2
Attachment B RAS Assessment
RAS Name
Path 18 OMS
Reporting Party
PacifiCorp
Group Conducting Assessment
PacifiCorp Main Grid Planning
Rikin Shah
Assessment Date
December 19, 2014
Review the scheme purpose and impact to ensure proper classification, is it (still) necessary, does it serve the intended purposes, and does it continue to meet current performance requirements.
The purpose of the scheme is to alleviate thermal overload on the Antelope – Goshen 161 kV line for the N-1 outage of Antelope – Brady 230 kV line when the flows on Path 18 are heavy northbound. This designation of LAPS is appropriate due to the level of generation tripping (<1000 MW) and load loss exposure (<300 MW). Impacts are limited to thermal overloads on the 161 kV line (thermal protection present for the overloaded line) for failure of the scheme to operate. There are no system impacts for inadvertent operation of the scheme.
For flows on Path 18 greater than 184 MW south to north, study results indicate that the scheme is still necessary meeting its intended purpose to alleviate thermal overload on the Antelope – Goshen 161 kV line for the outage of Antelope – Brady 230 kV line.
Path 18 OMS scheme once armed opens the Mill Creek end of the Mill Creek – Antelope 230 kV line and inserts the reactor at Peterson Flats to prevent high voltages on the open ended line.
The existing thermal protection on the Antelope –Goshen 161 kV line that will trip the line for flows over its emergency rating in 2 seconds serves as a back-up to the Path 18 OMS scheme to protect the thermal overload.
Study Years
2013
System Conditions
Light load conditions with flows on Path 18 South to North at its SOL rating.
Contingencies analyzed
(select what applies)
N-1
N-1-1
N-2
Extreme
N-1
Date when the technical studies were completed
April, 2013 (Refer to NWE’s Summer 2013 SOL study report)
Does the RAS comply with NERC standards and WECC Criteria?
Yes
Discuss any coordination problems found between this RAS and other protection and control systems during this (most recent) assessment.
None
Provide a Corrective Action Plan if this RAS was found to be non-compliant or had coordination problems during this (most recent) assessment (should be NA for owner’s initial assessment).
Based on the real time data and the amount of time the OMS has acted, PacifiCorp is holding discussions with other Path 18 owners to determine if the OMS is necessary or not.
Additional Notes
The flows on path 18 are rarely northbound as shown in Figure 1. Path 18 northbound OMS has never operated.
Figure 1: Flows on Path 18.