20180208PAC to Staff North Umpqua Runback RAS - Assessment.docx

PacifiCorp Main Grid Planning
PRC-(012 through 014)-WECC-CRT2
Attachment B RAS Assessment
RAS Name
North Umpqua Runback Scheme
Reporting Party
PacifiCorp
Group Conducting Assessment
PacifiCorp Area Planning
Assessment Date
12/17/14
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 North Umpqua Runback scheme is designed to mitigate overload conditions on the Dixonville to Toketee 115 kV line following loss of the Dixonville to Soda Springs 115 kV line.
The North Umpqua Runback scheme is listed as a Local Area Protection Scheme. This designation 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 local 115 kV transmission system for failure of the scheme to operate. There are no system impacts beyond partial and temporary loss of local generation for inadvertent operation of the scheme.
Study results indicate that the North Umpqua Runback LAPS is still necessary to mitigate thermal overloads on the Dixonville to Toketee Switching Station 115 kV transmission line following the loss of the Dixonville to Soda Springs 115 kV transmission line.
The scheme is effective for all seasonal load and generation conditions and is always armed.
Study Years
2014and beyond
System Conditions
The assessment was done with existing conditions depicting maximum total generation of 170 MW from the eight North Umpqua hydroelectric plants, for summer, winter, and lightload conditions. Loss of the Dixonville to Soda Springs 115 kV line results in an overload of the Dixonville to Toketee Switching Station 115 kV line. The problem is related to generation output, and not load or grid flow conditions.
Contingencies analyzed
(select what applies)
N-1
N-1-1
N-2
Extreme
N-1
Date when the technical studies were completed
May 2013
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).
N/A
Additional Notes
The assessment is valid until a system topology or generator change takes place because the situation is independent of load or grid flow conditions.